Natural Toxins in Food

The toxins in food are not limited to manmade chemicals. There are several toxins which are found in natural plants that we choose as food. Some can be neutralized through proper preparation techniques (soaking, fermenting or cooking the food), others are poisonous in any form. Here’s a list of some natural food toxins. Note that most are associated with plants.


Aflatoxin is a carcinogenic toxin in food which is produced by the Aspergillus flavus fungus. This fungus can contaminate foods such as grain, nuts and legumes such as peanuts. Aflatoxin-producing members of Aspergillus are common and widespread in nature. They can contaminate grain before harvest or during storage. Aspergillus lives in soil, decaying vegetation, hay, and rancid grains and nuts. Crops which are frequently infected include:

  • Grains such as corn, sorghum, pearl millet, rice, and wheat
  • Oilseeds such as peanuts, soybeans, sunflower seeds, and cottonseeds
  • Spices such as chile peppers, black pepper, coriander, turmeric, ginger
  • Tree nuts including almonds, pistachios, walnuts, coconuts, and brazil nuts. 

The toxin can also be found in the milk of animals which are fed contaminated feed. Virtually all sources of commercial peanut butter contain minute quantities of aflatoxin, but it is usually far below the US Food and Drug Administration's (FDA) recommended safe level for toxins in food.


Ergot is a toxin produced when the Claviceps purpurea mold infects rye and other grains. In medieval times, outbreaks of the disease “ergotism” were common and known as St. Anthony’s fire. The name was in reference the severe burning sensations in the limbs caused by vasoconstriction of blood vessels. The vasoconstriction sometimes resulted in gangrene and loss of limbs due to severely restricted blood circulation. The neurological symptoms of an ergot infection included hallucinations and irrational behavior, convulsions, and death. 


Goitrogens are a class of toxins in food which suppress the function of the thyroid gland by interfering with iodine uptake. Long term exposure can cause an enlargement of the thyroid (goiter). Foods containing these substances include soybeans (and soybean products such as tofu), pine nuts, peanuts, millet, strawberries, pears, peaches, spinach, bamboo shoots, radishes, horseradish, and vegetables in the genus Brassica (bok choy, broccoli, brussels sprouts, cabbage, canola, cauliflower, Chinese cabbage, collard greens, kale, kohlrabi, mustard greens, rutabagas, and turnips.


Hydrazines are volatile, carcinogenic toxins in foods such as raw mushrooms, including shiitake and the white button mushrooms common to the grocery store produce section. Mice display a significant increase in the incidence of several types of tumors after they are fed uncooked mushrooms. Cooking the mushrooms destroys a third of the hydrazine compounds.


Lectins are toxic protein compounds which are found in small amounts in many foods. However, many seeds, grains and legumes contain large, toxic amounts of lectins. Consuming high amounts of lectins can damage the heart, kidneys and liver, lower blood clotting ability, destroy the lining of the intestines, and inhibit cell division. Cooking neutralizes lectins to some extent, and digestive juices further destroy them but this depends on altitude. People living at high altitudes, where water boils well below 212 degrees should cook lectin containing foods in pressure cookers to avoid lectin poisoning. 

In addition, this paper discusses the ability of lectins to bind to insulin receptors on your cells, enabling the transport of glucose into the cell, much like insulin does. The import of this is that even vegetables and nuts, which are staples in a low carb diet, can stall weight loss if they contain active lectins which mimic insulin. Lectin toxins in food are found in:

  • Grains:  especially wheat and wheat germ but also quinoa, rice, buckwheat, oats, rye, barley, millet and corn, and all products made from them (oils, vinegars, alcohols, flours, etc..) 
  • Dairy foods: if the cows producing the milk are fed grains instead of grass (this would include most commercial milk products) 
  • Nightshade Plants: these include most plants in the Nightshade family, including potatoes, tomatoes, eggplant and peppers. 
  • Legumes and Beans: (all dried beans, including soy and peanuts and the products made from them).

Note that the lethal toxin ricin is made from castor beans, which contain large quantities of a particularly deadly lectin. Raw black beans contain enough lectins to kill rats in one week. This article discusses the health effects of lectin consumption in more detail. 

Dr. Steven Gundry has written an excellent book and a companion cookbook on this subject as well.

Opioid Peptides

Opioid Peptides: these are proteins which effect the brain and mood. Most people with food intolerances have digestive issues with wheat and dairy products. The common factor between these foods seems to be the opiate-like substances produced when the proteins from these foods are broken down during digestion. These opiate substances act on the body's internal opioid receptors, and can alter the perception of pain and affect respiration, digestion and mood. These opiate substances are found in the following proteins:

  • Casomorphin (milk) 
  • Gluten exorphin (wheat gluten) 
  • Gliadorphin/gluteomorphin (wheat gluten) 
  • Rubiscolin (spinach)

Phytates and Phytic Acid

Phytates and phytic acid are compounds found in many foods, but especially soybeans, whole wheat and rye. In the human gut, phytic acid acts as an anti-nutrient. Phytic acid reduces the absorption of valuable minerals such as calcium, iron, magnesium, and zinc by binding the minerals into an insoluble salt. Relatively high concentrations of phytic acid occur in the following foods: whole grain cereal foods (wheat, rye, rice, oats), nuts and seeds, soybeans, other types of beans, potatoes, artichokes, blackberries, broccoli, carrots, figs, green beans and strawberries. Soaking or sprouting the grain will neutralize much of the phytic acid, except in soybeans, which must be cooked for more than 10 hours at very high temperatures to remove the anti-nutrients. 


Psoralens are toxins in food products such as celery, parsley and parsnips. These compounds sensitize the skin to the harmful effects of ultraviolet radiation in sunlight, and as such are said to be photocarcinogenic. They are not destroyed by normal cooking procedures (boiling or microwave); thus humans are exposed to appreciable levels of psoralens through the consumption of celery, parsnips and other psoralen-containing foodstuffs. Psoralens are used to treat pigment disorders of the skin and other skin diseases such as psoriasis and nonmelanoma skin cancers.


Solanines are toxic alkaloids found in high concentrations in the green patches on and just under potato skins and eyes. They are also found in tomatoes, peppers, and eggplant. Solanine has both fungicidal and pesticidal properties, and it is one of the plant's natural defenses. The human body converts solanines into a poison called solanidine. Solanine poisoning is primarily displayed by gastrointestinal and neurological disorders. Symptoms include nausea, diarrhea, vomiting, stomach cramps, burning of the throat, heart arrhythmia, headache and dizziness. Hallucinations, loss of sensation, paralysis, fever, jaundice, dilated pupils and hypothermia have been reported in more severe cases. Experts say that a hundred grams of raw potatoes contain between 2 and 13 milligrams of solanine.

Experts believe that doses of 200 milligrams of solanine eaten at one sitting may cause problems. Symptoms can be gastrointestinal (abdominal pain, nausea, diarrhea, vomiting) or neurological (apathy, drowsiness, mental confusion, shortness of breath, weak and rapid pulse).

You can avoid solanine and another similar toxin called chaconine by avoiding green potatoes. Exposure to light or stress (or even aging) causes a potato to synthesize a green pigment called chlorophyll. Light, stress, and aging also cause the potato to produce chaconine and solanine. The appearance of chlorophyll is a warning that something is wrong with the potato. You should also avoid eating potato peels. About 30% to 80% of the toxin content of a potato is in its peel. Fortunately, these compounds are not well absorbed by the gastrointestinal system and are soon eliminated in the feces.

Trypsin Inhibitors

Trypsin inhibitors include toxins in food that reduce the availability of trypsin, an enzyme essential to protein digestion and metabolism for humans and animals. They are found in abundance in soybeans, and in lesser amounts in raw egg whites and lima beans. 

More Information About Toxins in Food

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