The Thanksgiving meal is chock full of potential toxins – which ones can be avoided?

It’s that time of year again, when cooks turn their attention to foods they will buy for the Thanksgiving meal, where they will buy them from, and how they will prepare them.  My mother was a scratch cook for the most part – homemade stuffing from bead crust, onions and celery, gravy from pan drippings, and mashed potatoes from spuds.  When I have made Thanksgiving dinner I have opted to use processed gravy, boxed stuffing and packaged mashed potatoes in order to spend less time in the kitchen and more time with my family.  My sweet potato casserole is more or less from scratch, but I need to disclose that I top it with mini-marshmallows.  I do not recall anyone ever getting sick from any of the Thanksgiving meals prepared by either me or my mother, except for the one Thanksgiving some friends brought a pumpkin pie and left it out on the back porch because it would not fit in the refrigerator.  People that ate the pie got sick and those that abstained did not.  Although it was cold as a refrigerator outside it was a sunny day; consequently the pie was not kept as cold as we thought.

In this day and age, more consumers are turning to fresh, organic foods for the Thanksgiving meal. Many are convinced that they are doing a disservice to themselves and their families if they use processed foods or produce from conventional farms.  Blogs are full of horror stories about the long term adverse effects of use of such foods. One I find particularly amusing states that “nearly every food made in a factory is bad for you”[1]. The same article advocates making raw pumpkin pies and exposing fruits and vegetables to minimal heat during cooking. Another article states that “feeding our kids with organic food will significantly reduce their exposure to pesticide residues”[2].  These articles as well as countless others posted on the internet are biased in that they do not mention any risks whatsoever to organic foods. The reality is that there is some risk of toxicity from eating any food.

Toxic substances are naturally present in produce, even if grown organically.  There is no escaping exposure to microorganisms, mycotoxins, heavy metals, bioactive substances and pesticides from food.  Some of the most potent toxins known are produced from bacteria and fungi. According to Bruce Ames (a renowned genetic toxicologist), “it is probable that almost every fruit and vegetable contains natural pesticides that are rodent carcinogens[3] ”. Some natural pesticides that are rodent carcinogens are present in plants and spices in part per million ranges, several thousands of times higher than levels of synthetic pesticides[4] .  Foods specifically mentioned by  Dr. Ames as containing rodent carcinogens, include vegetables and spices that are consumed at the Thanksgiving meal (i.e. celery, broccoli, cauliflower,  mushrooms, Brussels sprouts, parsley, parsnip, nutmeg, mace, nutmeg).  Furthermore, members of the Brassica genus (which include broccoli, Brussels sprouts, cabbage, cauliflower, mustard greens and radishes) also contain goitrogens, substances that suppress the function of the thyroid gland[5].  Lectins, substances which bind to and agglutinate red blood cells, are present in lima beans, kidney beans, peas and lentils[6]. Teratogenic glycoalkaloids (α-solanine and α-chaconine) are found in potatoes, particularly the peels, sprouts and sun-greened areas6.  I could add plenty more examples of toxins inherently present in produce, but I will stop in the interest of preserving the traditional holiday meal. Basing food choices on whether or not natural toxins will or will not be present is ill advised, because all food contains toxins. Poisonous substances are not poisonous if they are consumed at levels that do not cause poisoning. The trick is to minimize the amount of poisons consumed from food.  How can this be accomplished, when food is full of toxins? What happens to the food before we decide to purchase it is basically beyond our control (unless we grow it), but we have full control of the food once we select it.   A little common sense goes a long way in reducing the potential for poisoning from food.

First, choose produce that is in good condition and use it before it spoils. Plants that are stressed contain more toxins than healthy plants.   Concentrations of furocoumarins (substances with phototoxic and photomutagenic properties) in spoiled and diseased parsnips may be up to 2500% higher than fresh parsnips[7]. Infection with fungal pathogens induces production of the furocoumarins timethylpsoralen and  8-methoxypsoralen in celery, increasing  the potential for photodermatitis from celery handling[8]. Synthesis of α-chaconine and α-solanine in potatoes is stimulated by light or mechanical injury[9], and concentrations of solanine in green or blighted potatoes are increased seven fold[10].  Bruised or soft fruits and vegetables can be contaminated with mold below the surface and should be discarded[11]. If in doubt, throw it out!

Second, wash produce thoroughly to remove toxins and pathogens that may be present on the surface of food. In spite of advances in modern technology and efforts to provide safe food, foodborne diseases remain a major public health concern in the United States. Currently, it is estimated that one in six Americans (or 48 million people) gets sick, 128,000 are hospitalized, and 3,000 die of foodborne diseases per year[12].  An effective way of reducing the pathogen load on produce is to wash it. The FDA recommends washing all produce thoroughly under running water before eating, cutting or cooking, even if the produce will be peeled before eating[13]. Produce with rinds, grooves or waxy skin (e.g. cucumbers, winter squash, citrus, melons, potatoes) should be scrubbed with a brush. To prevent cross contamination, the USDA does not recommend washing a turkey[14].

Third, ignore the advice of food bloggers to use minimal heat when cooking produce, and use a high enough temperature to kill pathogens and inactivate heat-sensitive toxins. Cooking at temperatures between 70° and 100°C (158-212 °F) kills most bacteria[15]. High temperature cooking destroys goitrogens in Brassica vegetables and lectins in beans. Because cooking temperatures under 176 °F do not destroy lectin, use of slow cooking and/or a crockpot is not advised for cooking beans[16].  Turkey should be cooked to an internal temperature of 165 °F, gauged by a thermometer inserted into the innermost part of the thigh and wing and the thickest part of the breast[17].  If you are thinking about making a no-bake pie, scrutinize the ingredient list and make sure that none of the ingredients could cause food poisoning if they were uncooked. I have personally made a delicious no-bake pumpkin pie for some of my Thanksgiving dinners (which, by the way, did not sicken anyone), but it did not contain eggs, unpasteurized milk or fresh pumpkin.  The recipe is full of processed foods that contain approved preservatives, ensuring low levels of microbial contamination until the package is opened.

Fourth, store food appropriately. Contamination with pathogens is possible, even in foods that have been cooked at high enough temperatures to kill bacteria.  Cooked food can become contaminated with bacteria from food handlers, uncooked or undercooked food or utensils. Bacteria grow most rapidly in the range of temperatures between 40 ° and 140 °F, doubling in number in as little as 20 minutes[18]. Cases of botulism have occurred in people consuming salads prepared from foil-wrapped baked potatoes and sautéed onions stored at room temperature[19].  The USDA recommends for consumers to never leave food out of refrigeration for over two hours and to place leftovers in shallow containers for quick cooling and refrigeration within two hours18. It is likely that the pumpkin pie that caused sickness at one of my Thanksgiving dinners would not have done so if it was placed in the refrigerator from preparation to consumption.

Lastly, there is always the possibility of toxicity due to overconsumption of food. It is no coincidence that Gastroesophageal Reflux Disease (GERD) Awareness Week coincides with Thanksgiving every year, and ingestion of heavy meals has been associated with increased risk of having a heart attack[20]. Symptoms of myristicin intoxication (similar to alcohol intoxication) have occurred in people consuming approximately 5 g (1 tsp) of nutmeg[21], so don’t consume an entire pie or dish seasoned with a teaspoon of nutmeg at one setting! Most readers know about the risks from drinking too much alcohol, so I will not get on my soapbox about that.

To sum it up, the best way to reducing the potential for poisoning from a traditional Thanksgiving meal is to use good quality produce and wash it before use, cook food at temperatures necessary to kill pathogens and inactivate toxins, keep perishable food at room temperature for less than two hours, and limit what you eat. Watch what you drink, too. I sincerely hope that your Thanksgiving meal (as well as the leftovers) will be enjoyed by everyone at your table.  By all means, do not leave the pumpkin pie on the porch.

References

[1] Adams, M.2014. Is Thanksgiving food killing you?  How to choose holiday food that’s healthy, not toxic. http://www.naturalnews.com/047803_Thanksgiving_meals_holiday_food_toxic_ingredients.html.

[2] The Organics Institute.  2015. 14 key reasons why you should go organic. http://theorganicsinstitute.com/organic/14-key-reasons-why-you-should-go-organic/

[3] Ames, B.N., Profet, M. and Gold, L.S. 1990. Dietary pesticides (99.99% all natural). Proc Natl. Acad Sci USA 87:7777-7781.

[4] Gold, L.S., Slone, T.H., Manley, N.B. and Ames, B.A. 2002. Misconceptions about the causes of cancer. Risk Controversy Series 3. The Fraser Institute, Vancouver, British Columbia.

[5] Greer, M.A. 1957. Goitrogenic substances in food. Am. J. Clin Nutr. 5:440-444.

[6] Shibamoto, T., Bjeldanes, L.F. 1993. Natural toxins in plant foodstuffs. In Introduction to Food Toxicology. Academic Press, San Diego, CA, pp. 78-79, 82-84.

[7] Ceska, O., Chaudhary, S.K. Warrington, P.J. Ashwood-Smith, M.J. 1986. Naturally-occurring crystals of photocarcinogenic furocoumarins on the surface of parsnip roots sold as food. Experentia 42:1302–1304.

[8] Zobel, A.M.; Brown, S.A. 1991. Dermatitis-inducing psoralens on the surfaces of seven medicinal plant species. J. Toxicol. Cutaneous Ocul. Toxicol. 10:223–231.

[9] Tice, R. α-Chaconine [20562-03-2] and α-Solanine [20562-02-1].1998. Review of toxicological literature. Prepared for Errol Zeiger, National Institute of Environmental Health Sciences. http://ntp.niehs.nih.gov/ntp/htdocs/Chem_Background/ ExSumPdf/ChaconineSolanine.pdf.

[10] Jones, J.M.J. 1995. Food Safety. Eagan Press, St. Paul, MN, pp. 71, 77, 84, 87.

[11] USDA. 2013. Molds on food: Are they dangerous? http://www.fsis.usda.gov/wps/wcm/connect/a87cdc2c-6ddd-49f0-bd1f-393086742e68/Molds_on_Food.pdf?MOD=AJPERES.

[12] CDC. 2014. Estimates of foodborne illness in the United States. http://www.cdc.gov/foodborneburden/2011-foodborne-estimates.html.

[13] FDA. 2015. Raw produce: Selecting and serving it safely. http://www.fda.gov/Food/FoodborneIllnessContaminants/BuyStoreServeSafeFood/ucm114299.htm#prep.

[14] USDA. 2013. Washing food; Does it promote food safety? http://www.fsis.usda.gov/wps/portal/fsis/topics/food-safety-education/get-answers/food-safety-fact-sheets/safe-food-handling/washing-food-does-it-promote-food-safety/washing-food.

[15] EUFIC. 2015. Frequently Asked Questions; What is the danger zone where bacteria multiply rapidly in degrees Celsius? http://www.eufic.org/page/en/page/FAQ/faqid/temperature-limit-food-avoid-bacteria/.

[16] Buhler, R. Eating raw, undercooked beans can be unpleasant. High Plains/Midwest AG Journal. http://www.hpj.com/archives/2004/nov04/nov15/Eatingrawundercooke ddrybean.cfm.

[17] FDA. 2015. Food safety tips for healthy holidays. http://www.fda.gov/ForConsumers/ConsumerUpdates/ucm092815.htm.

[18] USDA. 2011. How temperature affects food. http://www.fsis.usda.gov/shared/PDF/How_Temperatures_Affect_Food.pdf.

[19] ICMSF. 2005.  Vegetables and Vegetable Products (Chapter 5). In Microorganisms in Foods 6 (2nd Edition). Kluwer Academic/Plenum Publishers, New York.

[20] Newswise, Inc. 2015. Study links heavy meals to heart attacks. http://www.newswise.com/articles/study-links-heavy-meals-to-heart-attacks

[21] Newswise, Inc. 2015. Study links heavy meals to heart attacks. http://www.newswise.com/articles/study-links-heavy-meals-to-heart-attacks