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Healthy Eating in the Tropics

Editor’s Note: We bring the following article to you not to scare you, but to arm you with information. Eating and cooking in the climate of the Yucatan is a different experience for many of us who come from more northern climates. From the time we first moved here from California, we noticed that fruit ripened and went bad much more quickly. We learned to freeze meat or eat it within a day or so, because it would even go bad in the refrigerator. We suffered on occasion from vague symptoms that could really only be attributed to what we had eaten the day before. And we were told, on more than one occasion, that parasites and worms were indeed something to take into consideration here.

Having lived with these facts for years, we were happy to see this article from the inimitable Dr. Stephen Fry, a man whose training and experience as a Public Health and Environmental Chemist with 34 years of professional experience makes him more expert than anyone we know on this subject. Of course, knowing too much about this subject runs the risk of making you want to get on the first plane to the Artic Circle. WIth that in mind, we have attempted below to deliver helpful information without overloading you with too much of it. As an academic, Dr. Fry has peppered his information below with citations of websites where the facts were gathered. We have included those citations for those who wish to check the facts or investigate further, but have tried to include them as unobtrusively as possible, for those who just want to read the article.

As promised, there is a lot of useful information here. Our first reaction upon reading it was an urge to go out and buy a lot of bleach, and we wouldn’t be surprised if you have a similar reaction. After sleeping on it, we’re still going to buy bleach and we plan to make some other changes in how we keep things clean. We appreciate Dr. Fry’s thorough treatment of this subject, and we encourage you to learn from it, "take what you need and leave the rest…" and do feel free to comment and ask questions at the end.

Living In the Tropics

Living happily in the Yucatan can involve a bit more than figuring out how to pay the CFE bills and deciding where to eat your next meal. But as it turns out, figuring out where and how to eat your next meal can be both one of the most rewarding experiences here, and one most fraught with peril. Anyone who has been here for awhile will start to hear about things like Chagas Disease (caught from the bite of a nasty Reduvid bug who drops down from a palapa roof while you are sleeping) or about someone’s bout with food poisoning. There are bugs here, big and small, that your mother surely didn’t teach you about. And it pays to know where they are and how to avoid them. In this article, we’ll be talking about the bugs too small to see, but powerful enough to make you extremely uncomfortable.

How Economy Affects HealthToilet

Let us start with a few observations from nationwide studies across Mexico, conducted by the US CDC (Center for Disease Control), NIH (National Institute of Health), Mexican hospitals, and Mexican Medical Schools. These statistics give us hints about why both tourists and expatriates normal and customary north-of-the-border hygiene habits may not work so well here on the Yucatan Peninsula and elsewhere in Mexico. Though certainly things have changed for the better in the last five years, this information is still an important clue.

Table Below: Comparison of socioeconomic indicators and prevalence of retail meat contamination and human Salmonella infection by state, Mexico, 2002–2005  (citation here). This table shows how economic factors directly affect how people live, and how they live affects their access to hygiene facilities and clean food. 


Yucatan %
Sonora %
San Luis Potosi %
Michoacan %

Population >15 that is illiterate or with incomplete primary education





Households with no toilet or latrine





Households with no sewage system





Working population earning less than $4 USD





Average prevalence of Salmonella in retail meat





Average prevalence of Salmonella in diarrheal episodes





Average prevalence of Salmonella in asymptomatic Children





While Yucatan is one of the safest places to live in North America relative to violent crime, this table demonstrates that everyone in Yucatan faces certain health challenges due to Yucatan’s overall poverty rates.  When you think about the people who handle food in the markets, grocery stores, and restaurants, keep in mind that over 40% of Yucatecans have no bathroom or septic system facilities and about 40% of them are illiterate or have very minor education.   Since even most literate Canadians and Americans have a limited understanding of practical microbiology and virology, you might consider that the person who prepares your salad may have even less understanding than you do of how to keep invisible microscopic tropical risks at bay. And as you read on, you may discover that your own understanding of these issues is not as comprehensive as you thought it was.

Meat Issues

The study results above also show that meat sold in a typical Mexican grocery store has equivalent or higher levels of salmonella contamination than was found in local animal intestine fecal samples.   Detailed analyses of the salmonella genotypes pointed to butchering practices as the most likely source of the contamination. This probably means that most Yucatecan meat starts out with pathogenic contamination, which then moves down the supply chain to your refrigerator, your countertop, or your favorite restaurant’s kitchen.   You might think these results for Mexico seem troubling, but think about this: the rates of contamination in the table above are actually roughly three times lower than the rates of contaminated US chicken: 83% of US chicken was found to be contaminated by either Salmonella or Campylobacter. Chicken in the mercado in Merida Mexico

So, you are probably asking yourself, if US chicken and other meats have similar or higher levels of commercial raw meat contamination, why would there be higher risks of getting food poisoning, worms, amoebas, or parasites in Mexico?

The experts from a study done by the CDC and experts at the O’Horan hospital here in Merida report, “…in the other states (like Yucatan), Salmonella spp. infections are probably acquired by other modes of transmission aside from contaminated food, such as from person to person or by contact with animal feces.  In settings with greater fecal-oral transmission, asymptomatic infections would not directly reflect contamination rates in the retail meat.”  

From this, we can conclude that understanding what your neighbor’s kindergartner who has no symptoms is carrying may save you a trip to the doctor or hospital. (From a public health perspective, it is worth noting that the Salmonella infections were also resistant to all tested common antibiotics (except Cipro) in about 15% – 20% of the cases. (citation here) From a personal perspective, this may not affect you but the statistic may encourage you to take a few more precautions.)

As we saw on the initial chart in this article, the following is true for the Yucatan (And if you plan to travel around Mexico, it’s good to note that Sonora, Michoacan, & San Luis Potosi were only nominally better):

  • 24.6% of Yucatan households have no toilet or latrine
  • 40.8% of Yucatan households have no sewage system
  • 16% percent of kindergartners walk around with endemic salmonella infections

This tells us that in many households in the Yucatan, the stage is set for bacterial invasion and infections.

Before we judge Yucatecans or criticize the state of these households too harshly, let’s do a reality check. How many readers mistakenly think that soap kills bacteria and microbes?  How many people reading this article wash their hands for 20 seconds (Two “Yankee Doodles” worth) of vigorously scrubbing with soapy suds on our hands)? When you are answering that for you and your friends, now consider how many (likely illiterate or generally less educated) food service workers know what is needed to stop salmonella transmission? Come to think about it, do you even know?

Past NIH tests of fecal coliform contamination of commercial fruits and vegetables in Mexico City consistently found high levels of salmonella in almost all samples, due largely to the use of “organic” (fecal – “night soil”) fertilizers and contaminated irrigation water. (citation here)

Your Body’s Ability To Fight These Things

If you recognize your daily exposures and take simple precautions that we will outline later, you can enjoy your time in the Yucatan, or anywhere in the tropics.  If you choose to ignore common sources of pathogens, and assume that your immune system will just handle everything, then you may find yourself in the hospital.   A little knowledge and a few precautions go a long way to staying healthy.

For those who believe "what doesn’t kill me makes me stronger”, consider that a number of food-borne pathogens can permanently alter the linings of your intestines. The cells of our micro-villi and intestinal walls regularly swap segments of DNA with bacteria and microbes in our food.   This means that snippets of DNA from any pathogens that you eat or touch, and then transfer to your nose or mouth, can get permanently incorporated into your intestinal lining’s cells. Your modified intestinal cells then can be "leaky" to future ingestions of pathogens, allowing some future microbes easy access from your gut into your circulatory system. Think of it as if you were passing out keys to your front door to a bunch of strangers.

After your intestinal epithelial cells’ DNA gets modified by some pathogenic organisms, it can leave you vulnerable to future attacks for the rest of your life. This is yet another reason to avoid unnecessary exposure to food-borne and contact-acquired pathogens, as this is a situation not addressed by our immune systems.

If those facts do nothing for you, then consider that we can often have low-level gastrointestinal parasites and/or pathogenic microbial infections that do not give us noticeable symptoms, but can leave us feeling a bit tired or rundown, as well as susceptible to colds or more serious infections, due to a heavily-taxed immune system. Eight million unnecessary cases of crud every year in Canada & the USA seems to rule out the idea that our immune systems will simply take care of exposures common pathogens. (citations here and here)

How Mexico Is Different

Typical Canadian and US food handling practices and dining and personal habits simply aren’t enough to address these facts:

  • Over 60% of Yucatecan meat is contaminated 
  • Many Yucatecan residents commonly have worms and their eggs, beasties that simply are not present in Canada and the northern USA
  • We enjoy ceviche (lime juice does not kill worms or encysted forms of worms inside the fish tissues)
  • Extensive use of night soil and pig waste to fertilize Mexican fruit and vegetable crops elevates our risks of food poisoning

These facts are game-changers that introduce pathogens like Salmonella Typhi and as many as four different kinds of worms that just are not a regular part of Canadian and US kitchens or Canadian/US market baskets.
Before you get too worried, keep in mind that most of our home environments are not loaded with harmful pathogens and our immune systems do offer some protection.   Outside of raw meats and a few kinds of fruits and vegetables, most foods do not regularly threaten us. If they did, we would be hearing about food poisoning outbreaks every few weeks. With some of the following precautions, we can be pretty sure that the meats, fruits and vegetables we eat will not harm us.

Practical Solutions: What Works and What Does Not

If you want to keep yourself and your family safe and healthy in the Tropics, it is important to find out what works and what does not in decontaminating the fruits and vegetables that you eat here.

The NIH study evaluating Mexican vegetable contamination found that the silver colloid-based fruit and vegetable disinfectant soaks (like Microdyne, Biodyne, etc.) lowers fecal coliform (bacteria from feces) counts, but does not eliminate them.   These same silver colloid products also did not remove salmonella typhi risks in any samples.  They found that only bleach-based disinfectant solutions (more on this later) were effective against all three major families of microbial contaminants tested. They killed fecal coliforms, salmonella, and various pathogenic mesophillic microorganisms.  It seems that peroxide solutions theoretically should offer similar protections from pathogenic microbes, but we have found no legitimate large scale studies to prove peroxide’s effectiveness.

Healthy practices boil down to three things: Washing your hands to disinfect is essentialy to health in the tropics

  1. Washing your hands well
  2. Regularly disinfecting oft-touched surfaces
  3. Handling known risky items like meat and fruit and vegetables appropriately 

If you know what you are doing and why, you’ll reap rewards with minimal effort and no stress.


Disinfect the things you commonly touch: Sink tap handles,  door knobs,  light switches,  the refrigerator handle, the toilet flush handle, stove knobs,  kitchen cabinet and drawer handles,  knife handles,  your car’s steering wheel,  your computer mouse and keyboard. Disinfect them regularly.   

Also, disinfect the surfaces and tools that touch likely-contaminated foods, like eggs (yes, especially the shells), vegetables, fruit or meat, and wash your hands thoroughly after handling them.  This keeps you from transferring the meat and fruit pathogens to other areas.

Finally, washing your hands thoroughly before eating and after using the bathroom is also very helpful.

When planning your cleaning and disinfecting strategies, remember that soap and hot water (as used in kitchen sinks) do not sterilize dishes or surfaces.  It takes scalding hot 145ºF deg water for at least 3 minutes of continuous contact to kill microbes, and our hands only tolerate about 108º – 110º hot water. Dilute bleach or peroxide work as well as and are a good substitute for hot water.

As you rank your risks, remember that our most important risks of microbial infections comes from a frequently soap-and-water-wiped kitchen and bathroom.  Since 60% of raw meat is contaminated with salmonella here, it is very important to disinfect your cutting board, knife, plate, and any surface that touches raw meat.  Kitchen sponge

Consider your kitchen sponge or wiping cloth. A typical North American’s kitchen-wiping practices, which involves using a damp sponge or cloth and soapy water, actually make kitchen surfaces, the refrigerator handle and stove knobs much dirtier than men’s bathrooms.  The best way to decontaminate these surfaces is to use a little dilute bleach or peroxide when wiping kitchen and bath surfaces. Otherwise, your sponge becomes a paint brush to smear the contamination everywhere you wipe.

Specifically when you clean your bathroom, focus on the toilet handle, faucet handles, light switches and door handles. A typical women’s bathroom is much more dirty, microbially speaking, than a typical men’s bathroom. So no matter what your gender, after using the bathroom, wash your hands thoroughly. By thoroughly, we mean rubbing and scrubbing for a full 20 seconds with soapy suds (whistling Yankee Doodle two times) to have a shot at significantly reducing microbes on your hands.

After dealing with raw meat handling issues, kitchen-wiping practices, hand-washing, and bathrooms, you must address the issues of the food in the kitchen. The best method for fruits and vegetables is to scrub and wash them first and then soak them in disinfectant (to remove feces-borne microbes on the outside).   Vegetable crops like lettuce are heavily fertilized with night soil or pig waste in Mexico.  You may want to reconsider Vendor in Merida, Mexicoeating salads in Mexico, because Salmonella typhi is present here at times, especially trapped in convoluted vegetables like lettuce. And Microdyne, Bacdyne, and other silver disinfectants only partly reduce microbial counts, and they do not touch salmonella typhi. These fruit and vegetable dips only kill about 80% of the potential pathogenic bacteria found here. The same issues do arise in Canada and the US, causing far too many deaths annually. Cantaloupes and bean sprouts and other things that cannot be scrubbed well are most likely the cause of roughly 8 million cases of food poisoning per year and roughly 1,000 deaths in Canada and the US every year from food borne pathogens. So you can see that these issues are not just in Mexico, but your chances of exposure are slightly greater in Mexico if you do not take some precautions.

Do you have a washing machine? Roughly 30% of Canadian and US home clothes washing machines are loaded with pathogenic microbes. There is an easy solution to this problem: run a bleach load as the last load.  This disinfects the pump and internal plumbing, which otherwise sit wet and  growing lots of gunk between loads.

Fallacy One: Soap

We’ve already discussed how “what doesn’t kill you makes you stronger” does not work for life in the Tropics. So now consider Mom’s advice on using soap and hot water to clean things.  Back in the Fifties, Sixties and Seventies, our mothers were mistakenly taught that soap magically kills bacteria.  It does not. Soap simply breaks up dirt, breaks up oils, and breaks up grease. When you can break up these things, you can rinse them away, along with the viruses, germs, bacteria and other microbes.   A recent USDA study found that cleaning fruits and vegetables by vigorous brushing is 97% as effective as commonly-sold fruit and vegetable spray cleaners, like Fit.  If you really want your fruit and vegetables clean enough for consistently safe consumption, no matter where you live, you need to scrub off all the dirt first, and then use a disinfectant like dilute bleach or possibly peroxide (see below).  (citation here)

Fallacy Two: Hot Water

Water temperatures that our hands can tolerate actually only plays a minor role in cleaning.  Warm water helps break up grease and oil by improving the soap’s or detergent’s action.  However, disinfecting with hot water takes three minutes or longer exposures to temperatures that burn or scald skin (145ºF / 65ºC).  So handwashing your dishes in hot water makes them look clean, but is not going to disinfect them.

Fallacy Three: Lime Juice

Love ceviche?  Do you think that lime juice and salt magically kills everything?  Time to hit the memory reset button.  Lime juice does not kill encysted parasites or worms in fish muscle tissue.  And unfortunately, typical studies find almost 100% rates of parasite infestation in many wild ocean fish. (citation here and here)

Properly prepared sushi, that has been sliced thin and carefully inspected on a lightbox, is a much safer bet than ceviche.   Carefully inspected and well-smoked lox can also be eaten with little worry of problems.

Fallacy Four: Freezing

Some people believe that freezing meat or fish is enough to make it safe.   In reality, raw fish must be frozen to an internal temperature of −20°C (−4°F) for at least seven days to kill parasites, which means that home freezers are generally not cold enough to kill parasites. (citation here

Fallacy Five: Big Grocery Chains

Meat in pretty packages at Americanized grocery store chains like Walmart, Chedraui, Soriana and Mega-Commercial  is tested, well-chilled, and safe, right? Unfortunately, as noted at the beginning of this article, we find that local meat sometimes goes bad in as little as two days.   After getting tired of feeding “bad” meat to the dog, I started watching meat-handling practices at these stores, checking out different stores repeatedly to try to find a good one. I found that employees routinely pack and unpack the cases of meat, leaving the meat sitting out warm in carts for one to two hours at all of these stores. While they are cleaning or arranging meat in the cases, microbes are multiplying. By the way, because the pH of dog’s stomachs is 100X more acidic than human stomachs, dogs relish meat that does not pass our sniff test. Dogs can eat meat that isn’t fit for humans and still live to tell the tale, but we wouldn’t encourage that behavior as a regular practice.

So, What Can You Do?

You can cook fish and meat to kill parasites and even encysted forms of parasites.   The USDA (citation here) offers this helpful reference table to remind us of safe internal temperatures for cooking meat, poultry and fish:





Minimum Internal Temperature & Rest Time

Beef, Pork, Veal & Lamb


160 °F

Steak, chops, and roasts

145 °F and allow to rest for at least 3 minutes

Chicken & Turkey


165 °F

Ground, stuffing, and casseroles

165 °F

Whole bird, legs, thighs, and wings

165 °F


Any type

160 °F

Fish & Shellfish

Any type

145 °F


Any type

165 °F


Fresh or smoked (uncooked)

145 °F and allow to rest for at least 3 minutes

Fully cooked ham (to reheat)

Reheat cooked hams packaged in USDA-inspected plants to 140 °F and all others to 165 °F.


Feel the packages in the cold cases of each store here, and if you find the meat warm to the touch (i.e., room temperature), walk away.   The only completely reliable solution is to buy meat that is still frozen, as it is sold at Super Aki and at Costco, or to buy prepackaged meats like ham.   Costco also seems to do a better job of butchering and storing their meat, but this is stricly an observation.  Some people rely on fresh-killed meats from local butchers, but all it takes is one fly to land and even that meat will have surface contamination.

Fortunately, typical bacterial contamination is only on the outside of meat, and it will be killed by cooking.  This is not true for hamburger and ground meats where the grinding process distributes the contamination throughout the meat. Hamburger should only be used when it is fresh, and it should be cooked to the higher internal temperature of 165ºF.   This means that well-cooked meat (thoroughly maintained at temperatures above 145ºF for at least 3 minutes) is generally safe from bacterial, protozoan, and amoebic contamination. 

It is also worth noting that the high percentages of salmonella on retail meat probably also translates to salmonella on the outside of the meat packages. To avoid contaminating your hands by handling meat packages, then touching the handle of the shopping cart and your car’s steering wheel, shop for your fruit and veggies first, and pick up some extra plastic bags.  Slip the bag over your hand (like a glove), pick out your meat, and then invert the bag back over your meat package. That will keep it all clean:  your hands, the shopping cart handle, and your car door handles and steering wheel.   Ever wonder why some grocery stores have begun to offer disinfecting wipes or gel as you enter the store?  They want you to use it to clean that cart handle that one-hundred or so other people have handled, most of them without taking these precautions.


All of this boils down to eating foods that come right out of a boiling pot, steaming tray, or hot oil and handed to you with clean paper or a clean plate. Wash your hands before and during food prep.  Disinfect your meats and fruits and vegetables and the tools that touch them.  Be cautious about relying on Microdyne, Bacdyne, and similar products because they just don’t work that well (and no, even though their names imply having iodine as an ingredient, they actually use colloidal silver).

Remember that short hand-washes also do not work, but learning to not touch your mouth, nose and eyes really does help. Soap and hot water do not disinfect things nor do they kill microbes. Soap and water simply remove dirt and grease that offer places for microbes to grow.

To kill microbes (i.e., disinfect) and to eliminate the hazards described above, you have these choices:

  • harsh chemicals (like dishwasher soap) and high temperatures (3 minutes @ 145ºF or 65ºC), in other words, a dishwasher
  • chemical disinfectants (like dilute bleach solutions… more below)
  • crown ethers (as in bar-glass washing solutions)
  • triclosan, as in antibacterial soaps
  • peroxide
  • alcohols, like the hand disinfectants popular since H1N1 flu outbreaks

Bleach Dilution Schemes for DisinfectionBleach as disinfectant and cleaning aid

Here are the recommendations for bleach solutions to disinfect the most commonly infected areas or items in your household.

  • Stored Water Treatment (tinacos etc): 10 mL (1 tsp) bleach per 100 L of non-turbid clear water or 1/4 cup of bleach per 275 gallon tinaco makes water microbially safe in 15 minutes.
  • Toilets and Sinks: Apply bleach without dilution via spray or brush for 10 minutes and rinse.
  • Drinking water: 2 drops of bleach per liter of clear water (20 drops per mLstrong) and wait 15 minutes.
  • Fruits and Vegetables: Wash & scrub thoroughly first to remove dirt, then 10 drops of bleach per liter of water and soak for 5 minutes. Rinse thoroughly.
  • Floors and bathroom surfaces (tub & shower): 1/4 cup (60 mL) bleach per gal of wash water and leave it on the surface for 5 minutes before rinsing.
  • Children’s Plastic Toys: Remove dirt first with soap and water, then use 1/4 cup (60 mL) bleach per liter of water and soak for 5 minutes and rinse.
  • Baby Bottles & Nipples:  1 drop of bleach per liter,  soak for 2 minutes and rinse.
  • Other Plastic Objects: Apply straight bleach for 5 minutes and rinse. Note that this might cause a permanent bleaching of some plastics.
  • Glasses and Plates: 1/4 cup (60 mL) per gallon of dish-washing soapy water, scrub off food residues, and allow to soak for 5 minutes.

Only use unscented normal bleach for these purposes. Do not use scented or non-splash syrupy bleach. NEVER combine bleach with any base (i.e., anything with a higher chemical pH). If you are not sure what that is, then do not combine it. NEVER mix bleach solutions with ammonia products or dried urine (concentrated UREA, like from an old mouse nest), because Base + Bleach = Toxic Chlorine Gas. (citation here re: various vegetable cleaning procedures)

Some people report that regularly dosing themselves with freeze-dried or other probiotic mixtures of beneficial bacteria and fungi can overseed their GI systems with microbes that put out the “No Vacancy” sign to incoming pathogens, giving them a type of "immunity" to these problems. We have no evidence for this, but we pass it on for further study or experimentation, though it is difficult still to find probiotics in Merida (other than capsules of lactobacillus,  which is also present in very low quantities in raw unpasteurized untreated yogurt).

Parasites and Treatments

Up to this point, we’ve described treatments for handling bacterial and viral contamination, with no mention of the other common health problems that arise from living in the tropics:  parasites.  I know of at least three different Yucatecan physicians who advise prophylactically treating yourself for worms, amoebas, and protozoans every 6 months here with anti-parasite medications.

There are a number of over the counter anti-parasitic meds sold at local farmacias for treating different parasites. The big choice comes when you decide if you want to include killing Cryptosporids in your treatment.

Some have found that "the cure is worse than the disease." When my wife and I used one (Daxon) that also treats Cryptosporids, we had a bad taste in our mouths and an upset stomach. Others, like the Working Gringos, have reported no side effects at all.  Some people choose Vermox, which works on many worms commonly found in Yucatecans.   The Dictionary of Specialized Farmacias says: "Vermox (mebendazole R17635) is effective against: Enterobius vermicularis (pinworm), Ascaris lumbricoides (roundworm), Trichuris trichiura (whipworm), Necator americanus, Ancylostoma duodenale (hookworm), Strongyloides stercolaris, Taenia solium, and Taenia saginata (tapeworm)." Who wouldn’t want to get rid of those?

If you choose to treat common worms, and amoebas, and protozoans like paramecia, then Vermox is not enough. It takes Metronidazole, or Ornidazole, or Secnidazole or Tinidazole or Daxon (Nitazoxanide) to handle that job. You can read this reference if you want more detailed background info: Clinical Evidence: Amoebic Dysentary. We suggest you talk with your local Mexican pharmacist or physician about what is best for your needs. Please note that OTC treatments are only effective for mild cases of amoebic infestations. Serious amoebic dysentery often requires multiple medicines taken over a longer period of time than the "one-shot" OTC treatments you buy at local Mexican farmacias, and should not be taken lightly.

Let’s Keep This In Perspective

Editor’s Footnote: By now, you probably have the keys in hand to go to the store to buy that bleach and you’re planning to visit the pharmacy too. These are not necessarily bad ideas, but we also don’t suggest panic. The suggestions about food handling and cleaning are good suggestions for anywhere you live in the world, but especially in the tropics and therefore, here in the Yucatan.

Are we going to stop eating ceviche? Not likely. Will we renew a bi-annual regimen of recommended medicines, something we were told to do when we first moved here? Yes, probably.

Dr. Fry reminds us of some statistics about the USA which might help keep this all in perspective. Almost all of us buy turkey and eat it happily at Thanksgiving in the United States. US Turkey was no better than Mexican turkey in past USDA studies, as it was found that roughly 50% of US retail turkey had salmonella. US Chicken has been worse, with 65% – 83% of retail chicken testing with salmonella and/or campylobacter in nationwide tests. On a more comforting note, US beef and pork were far cleaner, weighing in at under 5% found with salmonella.

As was written in the poem "Casey At Bat", there is no joy in Mudville. We all find no glee in telling these tales. But we do believe it is important to be informed. With knowledge and a little targeted effort, you can greatly improve your chances of good health for you and your family. We welcome your comments and questions and will do our best to answer them.

Steven Fry writes for Yucatan Living when he isn’t writing for his own blog, Yucalandia, for which we are very grateful.

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47 Responses to “Healthy Eating in the Tropics”

  1. Oy

  2. I am glad you have written this “warning” regarding steps and precautions we must take in our personal hygiene living here in tropical Yucatan. I was employed by the Wisconsin Health Department as a sanitarian. Trained to inspect water supplies-restaurants-milk processing plants-schools-swimming pools etc. I have been here living in Merida since January 2009 and have never…never eaten at any “hole in the wall” restaurant or any food from moving carts. Catch fisherman early in the morning returning from all night fishing to purchase your sea food and freeze it right away. Disinfectant bleach should be in your kitchen at all times and a water disinfectant pill should be put into your water tank up on the roof. Yes! Yes! Yes! you must “constantly” wash your hands..drink safe bottle water etc. You will always be as Happy as you want to be and enjoy life here in this beautiful tropical paradise. Thank you for sharing this information with all of us who have made Merida our permanent home.

  3. Thank you for this comprehensive article. I wash pretty much all vegetables and fruits in bleach treated water but not at the rates the doc suggests. That’ll change but the amount of bleach seems very high. Bleach is a carcinogen after all. I would like to have some feedback about that. Climbing up to the roof to tx the Tenneco is probably not going to happen. We use bottled water and bleach in the kitchen rinse water. The article implied rinsing meat in a bleach mix but was not clear about that. Should I be doing that? Jose suggests a “pill” for the tinaco. What pill is that?

    Thanks again. The article was very helpful and I look forward to hearing from the doctor or others about the pill, rinsing meat and upping the amount of bleach I use in the rinse water.

  4. Thank you for the informative article. Above Jose mentions a water disinfectant pill to put in your water tank on the roof. Please advise what they are called and where they can be purchased. Thank you

  5. The USEPA recommends 8 drops of REGULAR strength bleach per gallon for disinfecting drinking water. http://water.epa.gov/drink/emerprep/emergencydisinfection.cfm

    The rates of bleach listed above are for typical off-the-shelf ordinary strength commercial bleaches (4% – 6% sodium hypochlorite) sold at supermarkets. If you buy concentrated “Extra Strength” bleach (8% – 11%), then reduce the quantities of bleach added by one half.

    Chlorine “Tablets”: The USEPA further describes treating water with DRINKING WATER tablets:
    “You can use chlorine tablets to disinfect filtered and settled water.
    Chlorine tablets containing the necessary dosage for drinking water disinfection can be purchased in a commercially prepared form. These tablets are available from drug and sporting goods stores and should be used as stated in the instructions. When instructions are not available, use one tablet for each quart or liter of water to be purified.”

    The chlorine tablets you use for a swimming pool or spa also contain cyanuric acid to stabilize the chlorine in the pool, protecting it from UV sunlight degradation, so it should only be used on OUTSIDE swimming pools. There are downsides to adding pool chlorine tablets or spa chlorine tablets with cyanuric acid, because the cyanuric reduces the free chlorine ~ which is a problem, because it is the free chlorine that kills microbes. Several US state departments of health set maximum cyanuric acid levels for OUTSIDE swimming pools at just 100 ppm, but it should be noted that this level is based on swimming in the water, not drinking it. Further, a 2007 study by the Centers for Disease Control and Prevention (CDC) revealed that cyanuric acid significantly diminishes chlorine’s ability to inactivate the chlorine-resistant protozoan, cryptosporidium. Based on the findings of the CDC study, health departments recommends that cyanuric acid levels not exceed 30 ppm – which is easy to do if you use pool tablets or spa tablets in your tinaco.

    Re bleaching meat: Since microbial contamination of meat occurs primarily on the outside, a simple rinse of the cut of meat with water and then cooking it to the temperatures listed above is enough to kill pathogenic microbes in meat – unless you turn your meat with a fork. Poking the meat with a fork can inject the superficial microbes down into the meat tissue. If you choose not to use tongs, etc, and instead use a fork, then cook meats to 165º F inside, as you would hamburger and ground meats.
    Dr. Steven Fry

  6. Bleach is an aqueous solution of Sodium Hypochlorite. Sodium Hypochlorite (bleach) by itself is NOT carcinogenic.

    Chlorination of water does have a possibility of creating Trihalomethane compounds (THMs). The WHO has carefully evaluated the carcinogenicity of THMs, since bleach is so commonly used to disinfect drinking water. See: http://www.cdc.gov/safewater/publications_pages/thm.pdf from the CDC In Table 1, the WHO describes the carcinogenicity of THMs and chloroform as:
    “Inadequate evidence for human carcinogenicity. – Possible human carcinogen.”

    After 30 years of study, there is no solid evidence that THMs from chlorination of drinking water are carcinogenic. The USEPA does set exposure levels for THMs and other disinfection byproducts, but strictly following their guidelines would stop people from using public swimming pools,

    If you are actually worried about chlorinated byproducts of treating drinking water, then you should likely stop taking showers or baths. We experience far higher exposures to chlorinated byproducts in drinking and tap water from taking showers and baths than from drinking the treated water or washing dishes or cleaning foods.

    For people who are very concerned about chlorinated byproducts – and who don’t want to have to install a huge RO system or huge GAC system to take non-chlorinated showers or baths, you could consider putting a special shower head or tub faucet that contains zinc beads, that neutralize the chlorinated disinfection byproducts.

    The issue of THMs and other chlorinated byproducts is actually rooted in the Total Organic Content (TOC) of the water. Less than TOC of 2-4 ppm in the untreated water is cited as safe for chlorination. http://www.env.gov.bc.ca/wat/wq/BCguidelines/orgcarbon/drinking.html

    Since TOC comes from rotting leaves, dead animals, fecal matter, hog, cattle or chicken confinement operations etc, then typical deep well water like Merida’s, has very little TOC. If you are attempting to treat pond water, cenote water, somewhat nasty river water (like Mississippi river water), or shallow well water that is in contact with fosa septica or sumidoro wastes, then chlorinated byproducts might be a significant issue. Since natural forms of TOC tend to be colored, if your water is brownish or tea colored, then chlorination may not be your best choice.

    Merida ‘s municipal JAPAY drinking water, as supplied to our homes, is actually quite clean. http://www.ncbi.nlm.nih.gov/pubmed/7676351 It comes from deep wells drilled to approximately 350 feet, where the water quality is quite good. The problems with home tap water quality in Merida typically occur in the household plumbing / tinacos.

    The very small risks of health problems from bleach/chlorine disinfecting are much much smaller than the known and frequent health problems that come from Salmonella infections, Campylobacter infections, worms, protozoans, amoebas and other parasitic infestations, dysentary, giardia, fecal coliforms, and their little friends.

    My personal take on these things? : Enjoy taking showers, wash your hands frequently; learn to not touch your mouth, eyes, or nose; learn not to touch surfaces in public like hand rails etc; set-up a spray bottle of diluted bleach for spritzing counters and handles; hug & kiss your spouse or sig, other frequently; disinfect raw fruits (without a peel) and handle meats appropriately; . . . get plenty of good sleep; enjoy relaxing with friends or a good book; enjoy walking and regular exercise; develop good habits so you don’t have to sweat the small stuff, and enjoy life.

    Hope this helps keep things in perspective,
    Dr. Steven M. Fry

  7. Dr. Fry – thanks for this very valuable insight. It also confirm some of the practices that we currently use but also highlights other things that we ought to be doing as well, such as the use of bleach as a disinfectant.
    A couple of questions – We live just outside of Merida and have filtered, softened and UV treated water from a well that is quite deep. This water is plumbed to the entire house. We also have a reverse-osmosis set up for drinking water and ice in the kitchen. When we disinfect our veggies and fruit, we do this as soon as we get home with microdyne (soon to be microdyne and bleach) We then rinse the produce with our treated well water to cut down the taste/smell of the microdyne before refrigerating. What is your opinion about this procedure?? Looks like we should also look at a dish washer to sanitize our dishes. Does using running but treated (cold) water help when doing the dishes?

    We also have a tinaco on the roof that is used in emergencies – it is full of water all the time but is little used – is there an easy way of adding bleach or ??? to ensure that the water does not become contaminated??? Another commenter has suggested tablets but our tinaco is not easy to access. Any suggestions?

    I was also surprised that so few Yucatecos have access to WCs and sewage systems. I know that the Governor (not sure if it was Ivonne or before) has instituted a program to set up toilets, washing/shower facilities with septic systems in the pueblitos. These are prebuilt and are solar powered. Seemed like a good idea to me. The cost was quite reasonable, as I recall. The units were built in Merida.

    Many thanks,

  8. Typical Gringo overkill!

  9. As we said, John, take what you need and leave the rest. At least we’re comprehensive!

  10. Interesting article with some good and obvious tips but I think there is more of a silver lining. When I took Microbiology I learned about the crazy workings of bacterias, viruses and other microbes (prions- now that’s some scary stuff!) but you also learn about the amazing innate and adaptive immune system. I prefer to wash my hands, vegetables and cleaning surfaces while getting sunshine, exercise, and having fun. All equally as valuable I feel for fighting microbes that exist everywhere!
    And I never understand taking parasite medications prophylactically. While it may not be pleasant, it doesn’t cost much to take in a stool sample to a lab and get it tested. Then you can have a doctor prescribe the appropriate medication if necessary.

  11. Wow Dr. Fry! Great article….don’t listen to “John.” My question is about eating rare steaks and shrimp ceviche. Guess I have to give up the rare beef since getting it to that internal temperature will make it well done. But….do shrimp have the same parasitic problems as fish? Also, other than lettuce and canteloupe, you didn’t say what other vegetables are a risk. What about avocados, bananas, pineapple, etc.? I would think that since they must be peeled they would be safe, but I also thought that about canteloupe since those have such a thick skin. Thanks so much for all the great tips. I’ll be retiring there within the year and will use every single suggestion!

  12. Steve:
    Thanks for the great article, especially the various ratios for solutions (with practical measurements). The only thing you forgot was that one should make those up wearing clothes that can bear the possible splash and ‘bleach-burn’, so you don’t ruin that favorite blue pair of pants.
    Lots of good stuff here.

  13. I am a former RN and Advanced Nurse Practitioner and I always washed all vegetables and fruits before peeling them and everyone thought I was nuts until I explained that by slicing through contaminated skins contaminated the fruit underneath. My husband always thought I did an overkill on melons in particular, as I scrubbed them with a brush, soap and water and rinsed copiously prior to slicing or working with them. After we had a very bad outbreak of salmonella in the U. S. with cantaloupe lasts year he finally recognized I was correct.

    Your article really pointed out to me that a dishwasher, along with a system to disinfect water coming into the kitchen is a must for the area…I don’t like to do dishes, anyway. The alternative would seem to be to wash the dishes and then submerge all of them in extremely hot, as in almost boiling, hot water with an appropriate amount of bleach in it. I carry disinfectant, as in the hand cleaners with me and I clean the surface of trays and arms on airplane seats, grocery buggies, etc. After I wash my hands well, and I mean well, when in public bathrooms, I save the towel, if they have them now, and open the door out of the bathroom with that and turn off the water if a knob is used. If not, then one is contaminating one’s hands after washing them. I also use the maneuvers I learned when scrubbing for scrubbing in to assist in surgery and for passing instruments. It all comes in handy.

  14. Thanks for the kinds words.

    Bundling the replies to questions in 1 reply:

    Dishes: If
    ~ your home and kitchen are reasonably clean
    ~ dish drying & storage is roach-free, ant-free, and fly-free,
    ~ you disinfect your counters when cooking & doing food prep,
    ~ you handle fruits, veg, and meat properly,
    ~ you wash your hands before cooking and prepping foods,
    ~ and no one in your home is sick,
    then the risk of problems from dishes is not likely worth worrying about. Normal dish washing with soap and water to remove oils, grease, and food is generally good enough – as long as you air dry them. Drying with a damp towel is notorious for spreading any minor microbial problems. This means that a dishwasher with an internal water heater that hits 145º F water is likely NOT necessary.

    Bleach & clothes:
    You are correct. The bleach goes in with just the whites, and make the whites your last load – to disinfect the pump and tubing, so, that not much grows as the machine sits with wet guts until the next laundry day.

    Steaks & Shrimp:
    ~ In theory, public health experts advise cooking all meat to 145º F internal temperatures for 3 minutes. In reality, the salmonella contamination in beef has been found on the OUTSIDE of the cuts (not hamburger). Since the contamination is on the outside, then cooking the meat in hot oil in a skillet or on a grill kills the exterior microbes. Practical microbiology would predict that: if the microbes are only on the outside, then if your preparations do not inject or transfer the microbes to the interior of the meat:
    ~ no poking with a fork
    ~ no cutting inspection slits in the meat
    ~ no putting chunks of meat on a skewer or wooden stick or metal rod that transfer exterior microbes to the interior of undercooked meat.
    None of these practices are a problem if you cook the meat to 145º internal temperature. In theory, if you avoid all these meat handling problems, then the cooking kills the microbes on the exterior of beef, even if the center is still pink.

    I do not personally advise it, but a number of Nebraska restaurants sell still-bloody hamburgers, because they know the butchers, the butchers keep their practices and equipment very clean, and they sell the burgers within a few days of the butchering & grinding. These NE restaurants report ZERO cases of food poisoning even after 30 years of selling bloody burgers.

    ~ Shrimp: Again, experts say to cook it to 145º F internal temperature. In 30 years of reading food safety and microbiological literature, I have seen no references to parasites in shrimp – but exterior microbial contamination can be an issue with shrimp. This takes us back to the meat handling issues raised above. No poking the shrimp, no shrimp on a wooden or metal skewer (unless you cook it to 145º F), etc.

    Fruit and veg issues:
    ~ Fruits with a peel are typically safe to eat – e.g. the microbes on the outside of the banana don’t penetrate into the fruit – similar with a carefully peeled mango – but don’t lick the unwashed peel. If you peel the pineapple, or avocado, etc, then there’s no problem as long as the peeling process doesn’t transfer exterior gunk onto the fruit/veg’s flesh.
    ~ Fruits and veg with smooth skins that can be scrubbed with a brush to remove tiny bits of soil and debris and then soak in dilute bleach. You can generally do ok with a microdyne or bacdyne soak, since these colloidal silver products reduce common pathogenic microbes by 80% or more, meaning you only get a small dose of microbes. If there is a typhoid outbreak, then completely skip the bacdyne or microdyne and instead go to soaking in dilute bleach – which nails ALL of the problematic pathogens.

    In your previous Microbiology class you note: “but you also learn about the amazing innate and adaptive immune system. ”
    ~ Did your Micro professor specifically talk about living in the Tropics and the different issues we face here?
    ~ Were there discussions of leishmania or Chagas & reduvid bugs?
    ~ Did your prof discuss how microbes in the foods we eat swap segments of DNA with your gut’s epithelial cells?
    ° Did your prof discuss how segments of ingested microbial DNA can become permanently inserted in your GI wall linings cells? – creating permanent portals that cause a leaky gut that has nothing to do with your immune system?
    ~ Did your prof discuss how eating beef and its common beef pathogens insert bits of their DNA into our gut DNA – creating permanent openings in the intestinal lining that future beef pathogens use to move directly into our bloodstreams?

    Our “amazing innate and adaptive immune systems” do not address at all, these common items that arise while living here in Yucatan. Tropical microbiology is different than US/Canadian microbiological issues – which is the point of offering this article.
    Emily’s point is overall very good. We shouldn’t try to create a sterile environment.
    If we can instead avoid introduction of big doses of microbes, then our immune systems can cope with much of what we are exposed to. On the other hand, I have just had 2 friends hospitalized for weeks with pneumonia and another one killed by pneumonia here. I have had another friend hospitalized for a week and laid low for a month here. I personally got Rotovirus here that knocked the stuffing out of me and has left my gut seemingly permanently more susceptible to problems –
    ALL of these problems were likely preventable by following a few simple precautions – like bleaching/disinfecting door knobs, light switches, computer keyboards, computer mice, the car steering wheel, and kitchen and household handles, along with a little care in preparing foods and frequent hand washing.

    Take a few precautions – learn and practice a few new habits – to live happy & healthy lives here.
    Dr. Steve Fry

    PS If you enjoy reading these sorts of tips about living in Mexico & the Tropics, you might also enjoy checking out Yucalandia: Surviving Yucatan http://yucalandia.wordpress.com/ with articles on everything from cars, taxes, Immigration and Customs issues, driving, etc.

  15. Oooops, I just realized I missed answering the question on treating water in a tinaco.

    The best option is to treat it (roughly ¼ cup per 1100 liters) by dumping in bleach – which chlorinates stored water to roughly swimming pool chlorine concentration levels.

    If you cannot access the (roof-top?) tinaco to open the top and add bleach, you could pretreat/disinfect the cistern or ground level tinaco water, that is used to fill the roof-top tinaco. (?)

    Be aware that cheaper pumps may have a cast iron impeller that does not like sitting for weeks in bleach treated water – making the impeller rust. If you want to treat the ground level tinaco or cistern, realize that you may want to flush the ground-level pump with fresh water after filling the upper tinaco, to keep the ´pump from rusting.
    Dr. Steven Fry

  16. Wow! Great article!

    So you suggest soaking vegetables in the mild bleach solution, and then “rinsing thoroughly.” Given that tap water is suspect (especially in other parts of Mexico), are you suggesting we rinse our veggies in bottled water? Or, will the hypochlorite in the bleach evaporate, given enough time? Or is there another solution to getting rid of the chlorine/hypochlorite that doesn’t require so much bottled water?


    Kim G
    Boston, MA
    Where we are already fairly alert to bacteria.

  17. Hi Kim,
    Since 97% of Merida tap water was found clean for microbes, if your home water system is clean (bleaching the water in your tinaco as advised above), then it should be fine to rinse your vegetables with the tap water.

    The main goal of these efforts is to dramatically reduce your exposure to microbes that may be harmful at high levels or high doses, and to eliminate the likelihood of getting infested with parasites. There is no way to get our homes to operating room levels of disinfection, and we should not to try to create sterile environments.

    Applying this logic to fruits and vegetables: Most of the contamination is found in dirt, oils, waxes, or sticky sugary residues (like on mangos) on the outside of the fruits and vegetables, particularly those that are fertilized with human “night soil”, pig waste, and other manures that are loaded with pathogens. Scrubbing and washing are our best, most effective steps at reducing the numbers of microbes.

    If you then use Microdyne, you knock down the remaining bacteria by at least another 80% – except for salmonella typhi. Alternately, dilute bleach soaks kill everything that might put you at risk, killing germs, bacteria, viruses, et al. If there is a typhoid outbreak, then we really need to use bleach soaks, but fortunately, there have not been any reports of salmonella typhi outbreaks in our area.

    Since your home tap water in Merida is very very likely clean, the small amounts of water left on a vegetable (less than 500 microliters for smooth skinned things)will likely be trivial – especially if you air dry the fruit or veggies because the volume of residual tap water is so tiny. Alternately, if you have a shallow well, or you suspect contamination in your home plumbing, then you should consider brushing your teeth, rinsing fruit, etc with purified water. With all the 10,000′s of sumidoros and fosa septicas leaching our household septic waste into the first 30 ft of the Yucatan water table, shallow wells are often contaminated by the waste from our toilets.

    A US ground water expert who has been studying cenotes and Yucatecan ground water since the early 1960′s used to prove this by flushing blue food dye down a toilet, and then running people’s tap water from their shallow well into a white bucket. He reports that the water at the sink tap can turn blue within 15 minutes of flushing. In this kind of system, I would use a lot of purified water for ordinary kitchen and bathroom tasks.

    Recounting the key points: Our main goal is to reduce our chances of getting sick by making minor changes in our household cleaning practices and food prep practices. By taking a few regular precautions, along with hand washing and proper food storage and preservation, we can dramatically reduce our exposure to harmful microbes, and avoid unnecessary colds, food poisoning and greatly reduce our chances of needing unpleasant hospital stays.

    Take a few precautions, and enjoy this beautiful place!

  18. I have gone through the NYC food safety course and will agree with th above. I love using bleach in the kitchen and on floors.
    I take solice in the fact that people have lived here for hundreds of years and have not wiped themselves out and the remarkable human immune system.
    Here are a few tips I would like to add, always peel cucumbers, their skin is especially acceptable to holding fetrilizers and wax coatings, cook meats to reccomended temps., if you find yourself in a place with questionable food, eat less, hving less food in your system allows your body to fight off things much better then a full stomach, store meats at the bottom of your fridge, dripping juice can containate fruits and vegi’s., watch how you handle meat and then use the faucet in you kitchen, you might be re-contaimenating your hands when you turn off the water.
    I have never used micodyn or other cleaners here in the Yucatan and have never had a problem. In fact eating at a lot of small restaurants, I have had no problem either.

  19. Dr. Fry………….very good informative article. I appreciate your taking the time to put this together…… Most of us like to get out to a restuarant for dinner now and then…any recommendations for this venue……………..

  20. If our readers still think this is just hyperbole, and that tropical conditions like flies landing on raw meat hanging out in open-air markets or flies landing on pastries or seafood, you could check out a foto ofcommon fly behavior at YoListo: http://www.yolisto.com/index.php?/topic/4975-tiendas/page__pid__55550__st__20#entry55550

  21. Okay this will be a way out there question but here goes. What about the treatment of the pork, chicken and meat products purchased at any of the neighborhood markets or the big market????

  22. Patti,
    Open air markets with lots of flies indicate that it would likely have surface contamination. Follow the instructions listed above for proper handling of raw meat and kitchen items that come into contact with the meat, and then cook as described above to the internal temperatures listed in the table above.

  23. The fruit and veg disinfection scheme presented above has caused some people to reply with worries like: “By dumping into your body all of the chemicals suggested to “sterilize” your food, you are also destroying the very things in your gut that are helpful.”

    Let’s compare the amount of bleach that is left on food from soaking veggies in 10 drops of bleach per liter of water. The amount of bleach residue in a serving of veggies (i.e., chlorine left after disinfection) is very small. There is 860 times less chlorine from disinfection of vegetables than the chlorine present in a glass of tap water. Similarly, the tiny residue of bleach from disinfecting a serving of vegetables is 5700 times less than the bleach your body absorbs from taking a shower in chlorinated tap water.

    Since smoking related deaths account for roughly 500,000 US deaths per year, and ALL contaminants in drinking water cause only 250-1000 US deaths per year, being around smokers is 420,000 times riskier than eating disinfected vegetables.

    In terms of actual (increasing) relative risks, here are some interesting numbers:

    • 520 times higher risks of death from 3 glasses of water vs. 5 servings of disinfected vegetables per day
    • 1,150 times higher risk of death from 1 shower per day vs. 5 servings of disinfected vegetables per day
    • 28,900 times higher risk of death for driving vs. 5 servings of disinfected vegetables per day
    • 103,500 times higher risk of medical error death vs. 5 servings of disinfected vegetables per day
    • 420,000 times higher risk of smoking related death vs. 5 servings of disinfected vegetables per day

    10 drops of 5% bleach in a liter of water is a 1:2000 dilution that results in a disinfectant concentration of just 0.025 g of bleach per liter. 25 milligrams in a liter is a tiny amount. When you rinse the food with water, at most 2% of the original solution remains, which means that at most 0.0005 grams of bleach per LITER of bleach remains on your lettuce. For 0.5 mL remaining of the rinse water with tiny residues of bleach on your food, you then have just 0.0000007 g of bleach on the lettuce.

    If you believe that 0.0000007 g of bleach will affect the bacteria in your stomach, then you should probably stop drinking tap water nor should you ever take a shower.

  24. Please make it perfectly clear that this person is NOT a medical doctor at all, but a PhD. Nothing wrong with PhDs, but they are not Doctors, and the repeated use of “Dr” confuses the issue greatly.

  25. Consider it done.

  26. Hey Casi,
    You’ve made a good observation.

    Physicians, ( a.k.a. Medical Doctors) generally do not have much training in Public Health, nor do physicians study much microbiology – especially with little experience nor training in the food safety items discussed above. Physicians generally also have no background in food testing, nor do physicians have training in water treatment nor water testing nor water quality. Physicians typically have no training in evaluating nor protecting food quality.

    Physicians generally have minimal training in the chemistry of disinfection, and know little about food chemistry, water chemistry and soil chemistry. Physicians are generally untrained and have little experience in research or working in scientific laboratories. Physicians are well trained to memorize anatomy, physiology, the symptoms for 10,000′s of medical problems, etc., and physicians often only have modest introductory training in the hard sciences of chemistry, physics, etc.

    I’ve had extended conversations on these points with my brother-in-law and other physician friends. My brother-in-law is a fine physician who was also the head of Medical Education at University of Kentucky Medical School and the head of the Research and Residency programs at University of Richmond Medical School. At University of Rochester’s Medical School, he was in charge of research and training physicians to work better with patients.

    To give people some perspective on the skills of physicians, one Sunday conversation he related how even with his extensive time as a professor/teacher in charge of training physicians, the last time he “really had to think” was 25 years before in his third year of undergraduate studies in a Physical Chemistry class. Physician friends relate similar stories… that their time in Med School and Residency was spent memorizing vast amounts of information on illness and disease.

    So, yes, Casi has a fine point. It’s good to know who is offering you advice. Each kind of doctor has different qualifications and different training from other kinds of doctors.

    I am a Doctor of Chemistry, with 35 years of training and specialization in Public Health and Environment, including evaluating and ensuring the safety of Food and Water supplies and the associated testing capabilities.

    If those qualifications do not suffice, here are a few more. After the break-up of the Soviet, I was the first Western Scientist invited into the Former Soviet Republics to evaluate and advise the Clinton Administration on Public Health, Water Quality, Food Quality, Air Quality, and Soil Quality, with a special focus on Ukraine in the post-Chernobyl era. Based on the success of that effort, I was then invited to Moldova (later Belarus) and then to Tadjikistan by the US Government. I have worked on projects for roughly 17 different US states’ and 5 countries’ Public Health agencies, and have authored four methods for the US EPA.

    So, Casi is correct. It’s very important to recognize the expertise of medical doctors, and to not confuse a medical doctor’s training in diagnosing and treating disease and illness, with a scientist doctor’s roles in Public Health issues. Physicians are generally not scientists nor Public Health experts. Scientists and Public Health experts generally have little training in diagnosing illness.

    Choose the expert whose training and experience fit the problem.
    Dr. Steven M. Fry

  27. Glad we cleared all that up! :-) Thank you BOTH for your participation and for help in clarifying some issues.

  28. I would like to introduce another disinfectant to this conversation and would love to hear your take on it: vinegar. For the four years that I have lived in Mexico I have always used vinegar, yes, the plain household stuff ‘vinagre blanco, de alcohol de cana’ with 5% acidity. I have never had any problems. Was I just plain lucky?

  29. Victoria,
    We can’t predict which times we need effective disinfection and we can’t predict exactly which microbe will strike or when. Your home-grown method of using vinegar may work with small low level infestations of mild fecal coliforms or minor salmonella exposures – lulling you into a state where you believe you are well protected.

    At some later point, when your kitchen face some of the common but nasty microbes, like Salmonella typhimurium, Salmonella enteritidis, Salmonella Heidelberg or Salmonella newport, or Rotovirus, a mild treatment like vinegar won’t be enough.

    50% of raw meat across Mexico contains some type of salmonella. I have had 2 friends hospitalized for over a week apiece, and both took over a month to recover from garden variety microbial GI infections here in Mexico. I prefer to use simple easy-to-use methods that have decades of proof of reliability, rather than face prolonged hospital stays over something that can be cheaply and easily prevented.

    Dr. Fry

  30. Fantastic article and discussion. I seem to be doing most things right, but hadn’t thought about double bagging the meat packages in the store…or watching out for the cart handles.
    Many years ago while living on Isla Mujeres I was always amazed that the meat vendor I used never had flies swarming on his chicken, pork, etc. Then one day I came to the market before it had officially opened and I saw him spraying his whole stall (including hanging meat) with an insecticide…probably DDT. I went back to eating only fish which I speared daily for myself. I guess it was reasonably safe as long as you knew where the sewage treatment plant dumped its untreated waste. Of course you had to hope that the fish you were eating hadn’t been swimming on that side of the island or that a storm hadn’t contaminated the entire area. YUM.

  31. I just returned from a month in Merida and surrounding pueblos. I wish I had read this article before I left.
    At the end of my visit, I experienced dizziness and edema. After returning both symptoms have continued and the edema has worsened. I also have gained an additional 25 pounds since returning. After reading this article, I’m beginning to wonder if I should get checked for intestinal parasites.
    I haven’t really had any other symptoms but can’t seem to lose the weight in spite of going on a juice fast for 10 days.

  32. Even if parasites are not the problem, it is worth getting a medical lab test for Ova and Parasites. This test of your feces is commonly called an O&P. You can read more about it here: http://labtestsonline.org/understanding/analytes/op/
    “Getting an O&P” is code for seeing a Physician, having them examine you, and they order the O&P.

  33. I am an medical doctor (MD). Regarding the use of “Dr” in the author’s name, although it is a bit unusual for PhDs to use it, except in academic settings, I have thoroughly read the information presented here and have the following comments: 1) the info is well researched and extremely thorough presented, 2) the info is presented purely from a public health and epidemiology standpoint regarding sanitation and hygiene, 3) all the info presented is openly published in those areas and is readily available to any literate reader on the internet versions of research journals in those fields who wants to go to the touble of checking it for himself, 4) Dr. Fry makes no recommendations about diagnosing, advising, or treating patients for illnesses, but instead makes a really good effort to prevent disease. as he explicitly points out, and you don’t need to be an MD to do that, as any mother, housewife, chef, waiter, foodhandler, plumber, and so on, knows. I have no problem whatsoever with his use of the term “Dr”, and in fact think he did a hell of a good job collecting and presenting the info.

  34. Thank you Dr. Fry – I really appreciated your article and your response to the questioning of your doctorate degree. I also appreciated Dr. Dye’s comments as well!

    I live in the US and am planning to bring a group to Uaymitun. What do you suggest I do to prepare now, before we come out? Obviously coaching them on the cleaning issues, but are there any other things we should do ahead of time to prevent or decrease our chances of getting parasites? What about the probiotics? Do you suggest that?

    Thank you!

  35. Thanks for the kind words.

    Avoiding salads and ceviche seems to be the best courses to set. Bring wetnaps or your personal bottle of hand sanitizer, and wash your hands frequently – practicing 20 seconds of scrubbing with soapy suds.

    Probiotics are a particular favorite of mine. There have been some really fine articles in the NY Times et al describing the importance of having a robust group of microbes living in our gut, on our skin, and in our mouths. We personally have used various probiotic preps for the past 30 years, including various beneficial bacteria, fungi, and molds. In our experience, a good probiotic supplement includes a broad range of different types of microbes, including as many as 4-5 different species of lactobacillus, plus several species of Bifidobacterium like Bifidum longus, and various Pediococcus species.

    This advice and these approaches work for helping avoid incidental salmonella infestations, but do not work for some parasites and encysted worm eggs. Avoidance seems like the best advice when approaching parasites like worms, amoeba, and protozoans. You might also consider buying a dose of some of our over-the-counter anti-parasite medicines to take back home with you, because US pharmacies do not generally carry them, and US physicians are generally unaware of these tropical problems. Read all of the package inserts carefully, and strongly consider consulting a physician before using these medications, particularly if you have any liver or kidney complications.

    Best of all, relax, enjoy, sleep well, laugh, take a few practical precautions to reduce your exposures, and don’t stress out over these things.

  36. Sounds good

  37. I have physician friends in Guatemala who use a dilute iodine solution for vegetable washing. And of course, as a kid camping in the era before pumps, I used to use iodine tablets to purify water. I’ve looked online for references to compare bleach vs. iodine for vegetable rinsing but come up empty. Can you shed an light? Advantages and disadvantages? Thanks!

  38. I am not living in the Yucatan, but resided in Venezuela years ago for a few years and was trying to remember how much bleach I used in a sink full of water to disinfect raw veggies. After an internet search I came upon your article and found it to be very helpful. Call me paranoid, but these days, I’ve decided to clean my veggies even here in the States as thoroughly as I did when in S. America…
    Thanks for the information!

  39. Hi Josie,
    Good points with repeated E. coli, Salmonellas, and Listeria outbreaks in the USA over the past few years.

  40. I have been hearing conflicting information about the tap water in Merida. Is it safe to use municipal water to rinse fruit and vegetables and to cook with i.e. pasta? Are reverse osmosis systems worth the investment? We are currently in the process of renovating our home and deciding whether to go with the system or stick with bottled water. Thanks!

  41. Nancy, from what we could learn, there is not much difference between bottled water and the result of the reverse osmosis system, which we installed in our sink. We always used city water to rinse veggies and to cook with, except maybe when we made coffee. We’re still alive and kickin’ :-) Perhaps someone else has more technical information?

  42. Merida tap water in the pipes in the street is almost always safe to drink.

    The last big University study of roughly 375 households across Merida found that 19 out of 20 had no contamination at the meter. The 5% of homes with fecal coliforms in their water at the meter were in just one district.

    This past UADY water study results have been confirmed by a friend who sells water cooler-purification units found that every tinaco he tested, had sufficient levels of disinfecting free chlorine to meet US and Canadian public health standards …

    The same UADY study also took samples at the kitchen sinks of each home (in addition to at the meter), and that picture changed dramatically: 25% of Merida homes tested positive for fecal coliforms (pathogenic bacteria) at the kitchen sink tap.

    This means that 1 in 4 Merida homes had contamination in their tinaco or in their house’s plumbing – even though their property was receiving clean water from JAPAY.

    Moral of the story? Inspect your tinaco … and treat the water in your tinaco and your home water plumbing somewhat regularly with bleach. 1/2 cup of bleach in a standard 1100 liter tinaco gives you public swimming pool concentrations of disinfecting free chlorine.

    After adding the bleach to your tinaco, wait a half-hour for it to mix, then go around the house, flushing toilets, running the shower, and opening every every sink tap to run enough water till you smell a little chlorine.

    Let the chlorinated water stand in your pipes for 15 mins.

    If your tinaco and plumbing does not have lots of organic matter ( algae growing in rooftop PVC pipes… or old leaves, dead birds, etc), then this amount of bleach is enough to sanitize your home water system.

    Your shower water will smell like swimming-pool water for a few days, but it guarantees clean plumbing.

    I personally do this about 4 times a year – especially if we have guests/family coming to stay from America or Canada.

  43. Thank you, Steve!

  44. Thanks Working Gringos, in your opinion which would you recommend reverse osmosis or bottled water in your house, our archetict is recommending bottled water. We plan to live in Merida full time.

  45. Let’s just say that when we built our house, we put in a reverse osmosis system and were very happy with our decision.

  46. Different strokes for different folks.

    Reverse Osmosis (RO) units have water standing 24/7 for 365 days a year in their plumbing. Since the RO units remove chlorine, RO has ZERO capability for disinfecting the plumbing of the RO unit. Since the plumbing outlets of RO units are touched by humans, and by air that is loaded with mold spores, algae spores, and bacteria-laden tropical dust, unless you regularly soak that plumbing in disinfectant (like bleach), that RO plumbing grows bacteria, molds, algae, etc.

    No one I know has testing capabilities to show that their RO plumbing is still clean, 2 months, 6 months, 1 year later… How do the RO owners know their water is still clean?

    Since the bottled water companies (Pepsi and Coca Cola) regularly test their water, and since the bottled water companies disinfect their bottles every time, which water would you trust more a year, 2 years, 3 years later? I have an RO unit in our Colorado home and yes, I cleaned the plumbing, just as I disinfect/treat our tinacos here regularly, with bleach.

  47. Well, the obvious answer is we don’t know. We just know we aren’t sick yet :-) . Thanks for that explanation, Steve!


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