39 Plant Foods That Are Toxic

There are many plant foods that are toxic or poisonous.  Cassava (also called yuca or manioc) is a plant with a starchy root that is a popular food item in the tropics. The outer surface contains a glycoside that can cause poisoning of the body’s energy metabolism.  Processed  tapioca does not contain this poison.

West  Africa has a particular  problem with  this toxin, cyanogen, since people there rely heavily on cassava as a staple. Symptoms can include blindness (amblyopia) and nervous degeneration  (ataxic neuropathy). Lima beans, sorghum millet, kidney bean, garden pea, sweet potato, Indian gram, and almond also contain certain amounts of this cyanogen. By soaking and washing the food, the risk is reduced. By sprouting the food, risk is considerably reduced. Cassava should be avoided or at least not served as a staple. These common foods can be used as natural antibiotics.

A High Phytate Diet Can Stunt Growth

plant-foods-that-are-toxicOxalates are substances found in spinach, rhubarb, celery, beetroot, parsley, almond, and tea that bind calcium and other divalent minerals and carry them out of the intestinal tract. Phytates are similar substances with similar action but are found  in whole grains like wheat, rye, oats, and barley. In grains, the phytates are reduced considerably by the fermentative action of yeast. Thus unleavened bread is much higher in phytates. Both oxalates and phytates can lead to mineral deficiencies in large amounts are consumed and the diet is low in certain minerals. Residents of the Middle East consume a low-zinc, high-phytate   diet  that  can  stunt  growth   and  retard  sexual development.

Saffrole – A Cancer Causing Agent

The  natural flavor of root  beer used to come from sassafras. Sassafras contains copious amounts of saffrole, a cancer-causing agent, and therefore is now banned. Potatoes and a number of spices have harmless amounts of saffrole.

Poor Iodine Metabolism

plant-foods-that-are-toxicGoitrogens are substances found in plants that interfere  with iodine metabolism. Cabbage, turnip, cauliflower, kale, brussels sprouts, broccoli, and soybeans contain this iodine-binding agent. Regular intake of these vegetables in a raw state combined with a low-iodine diet could produce goiter in those with thyroid problems. Cooking these foods nearly eliminates goitrogens in the diet. Brussel sprouts can contribute to improved vision.

Lathyrogens are substances that are protein in nature and found in the garden plant vetch. The  lathyrogens in this pealike plant can cause skeletal deformities or paralysis if consumed to excess. In India, where vetch is usually a small part of the diet, this occurs only when availability of other foods diminishes.

Seeds of the cycad plant, found in the Pacific islands, are susceptible to bacterial attack when consumed and can produce a potent cancer-causing agent, cycasin. These seeds should be soaked, washed, and cooked to minimize the hazard.

Deadly Green Potato Shoots

Solanine  is a deadly chemical  found in sprouting potatoes that has an action similar  to nerve gas, disabling the central  nervous system. All potatoes contain some solanine, but only those exposed  to the sun and beginning to sprout contain deadly amounts. Potatoes with green  shoots  on them should be disposed  of.

Trypsin inhibitors are found  in soybeans,  peanuts, navy beans, and lima beans and  will  inhibit  protein digestion in the intestinal tract.  Steaming, cooking, or sprouting will deactivate  these potent substances. Lectins are another potent toxin  found in legumes  and neutralized by cooking or sprouting.

Raw egg whites  contain avidin, which  binds to the B vitamin biotin. Ex­cessive consumption of raw eggs could create a biotin deficiency. Cooking denatures avidin and renders it harmless.

Hemaglutinins are protein substances that cause the blood cells to clump together, thus impairing their  normal function and  potentially leading  to cardiovascular ailments. Found in soybeans,  Guatemalan red  bean, Indian red gram,  and  Philippine mung  bean,  these substances are inactivated by soaking the beans in water  before cooking.

Psoralens are a potent  carcinogen found  in all parsnips.

Comfrey tea is a favorite among some health enthusiasts. The leaves have been found to be carcinogenic in rats, and the leaves and roots can cause liver damage. Those people  trying  to pick  their own comfrey had  best be plant experts. Foxglove, containing the potent heart medicine digitalis, is a dead ringer  for  comfrey.

Caucasians who  are native  to the  Mediterranean area have an inherited vulnerability to illness when they consume fava beans. Favism causes illness in all people  and anemia in  young  children. Drying and aging of the fava bean reduces the toxicity.

plant-foods-that-are-toxicPlantains (a species of banana) contain  a substance that induces a common heart  condition in  the  Mrican tribes who  consume this  food regularly. Cooking significantly lowers the  risk.  Hypoglycins found  in the  Ackee fruit of the tropics can seriously lower blood sugar. Djenkolic acid found  in a bean popular in Indonesia causes the kidneys to excrete valuable body sub­stances. A purple  mint  plant  found  in the  United States and Asia (Perilla frutescens) can cause various lung disorders. The Great Plains of America produces some plants  that have unusually high levels of selenium  from  the soil and can induce  nervous disorders. Tetradotoxin is found  in the ovaries and liver  of the pufferfish and is lethal.

Ciguatera is a poison  found  in tropical fish such as grouper. The Centers for  Disease  Control in Atlanta estimates that  50,000  people  annually  are stricken with this toxin. This is the primary condition treated in emergency hospital  units  near tropical  coral reefs. Less than  I percent of the cases are fatal.  Certain fish, clams, and shrimp contain thiaminase, a substance that destroys  thiamin in the intestines. Thiaminase  is destroyed by cooking. The trendy raw fish (sushi) bars do not make good health sense for this reason and because raw fish may contain larvae of parasitic organisms, which are killed when cooked.

There are many other naturally occurring  toxins in food. Certain  mushrooms contain deadly poisons. Hemlock, renowned for its lethal effect on the ancient Greek  philosopher  Socrates, can also poison humans who eat birds or animals that have consumed hemlock.


Dr. Patrick Quillin

Dr. Patrick Quillin, PhD,RD,CNS is an internationally recognized expert in the area of nutrition and health. He has 30 years experience as a clinical nutritionist, of which 10 years were spent as the Vice President for a leading cancer hospital system where he worked with thousands of cancer patients in a hospital setting. He is a Best Selling Author with 18 books which have sold over 2,000,000 copies and also a Keynote Speaker.