A number of toxins in foods are produced by molds, algae and plants and can cause serious illness. Some of the more common are usually caused by plant toxins.
Safrole can be found in sassafras, mace, and nutmeg. It can cause cancer when consumed in high doses.
Solanine is found in potato sprouts, green spots on potato skins. It can cause nausea, diarrhea, vomiting, hallucinations, loss of sensation and paralysis. it can be prevented by storing potatoes in a dark area and discarding the sprouts, peel and any any green tinged spots.
Mushroom toxins are found in some mushroom species such as amanita. It causes digestive upset, neurological symptoms; more lethal species can cause liver and kidney failure, coma and death. Illness is almost always caused by wild mushrooms picked by non-experts.
Herbal teas containing senna or comfrey. Onset depends on the dose; diarrhea and liver damage can occur. These teas are used in folk medicine and are not considered safe for internal use.
Lectins are found often in raw or undercooked legumes, usually kidney beans. Other foods with a high lectin activity include: grains (especially wheat) soy, nuts, and nightshade plants (eggplant, tomatoes, potatoes, peppers. In high doses there is a quick onset of nausea, vomiting, abdominal pain and diarrhea. As few as 4-5 raw beans can cause symptoms usually due to under-cooking.
Illness from these toxins is rare. However, licorice contains a natural toxin that can elevate blood pressure and cause heart failure. There is cyanide in lima beans and almonds. When plants are stressed in severe environmental conditions, they tend to produce greater quantities of toxins since they use these toxins to protect themselves from molds, bacteria, insects and other predators including humans.
Humans have been dealing with these toxins for centuries by learning how to avoid or limit their intake. Cooking limits the potency of certain toxins, but not all. It would be unrealistic to try to avoid them which would limit food choices and variety in the diet. But it is important to realize natural toxins do exist and to eat a varied diet to avoid any single toxin is eaten in amounts that exceed our ability to detoxify them.
Arsenic has been in the news lately due to its presence in rice products. From a previous post, it has also been found in chickens. The following article from Marion Nestle offers some advice.