You may be surprised to find that many foods that we eat everyday can be toxic if not properly stored, or if you eat too much of them. For example, did you know that eating more than a kilo of potatoes in one sitting could be potentially fatal? Or that leaves from the tomato plant are poisonous? Here are some facts that will surprise you:
1. Potatoes. Wild potatoes have toxic chemicals called solanine and chaconine. The highest concentration of this is just under the skin, and their concentration increases as the potato grows older or has more exposure to light. Commerical potatoes are potato varieties which have been bred to reduce the amount of toxic chemicals in them. Nonetheless, the toxic chemicals do increase as the potato ages and turns green. Cooking at high temperatures (over 170C/340F) does destroy some of the chemicals, but does not eliminate them completely. The safest thing to do is to avoid wild potatoes, and don't eat any potatoes that have turned green. Also avoid potatoes that have been kept under sunlight or have been kept for too long. Fresh store bought potatoes are generally after being cooked, though in theory, you could get solanine poisoning if you ate several kilograms of potatoes in one day. Note that potato leaves have very high levels of solanine and are toxic. The symptoms of solanine and chaconine poisoning are headaches, diarrhea, cramps. Higher doeses can lead to death. Toxic poisoning occurs if you eat more than 2mg-3mg of solanine per kilogram of body weight. A fresh commercial potato may have up to 200mg per kg of potato. So for a healthy 70kg person, the toxic dose would occur if you eat more than 700gms-1.05kgs of potatoes in one sitting. Beware of potatoes that have been damaged, kept in the sun or gone green. They can have more than 1,000mg of solanine per kg of potato. In other words, eating a single bad potato can kill you.
2. Brazil Nuts. A raw unshelled brazil nut has about 100mcg of selenium. Selenium is a chemical element (atom) which the human body needs to survive, and some scientists believe that insufficient selenium may leave the body prone to cancer. However, Selenium is considered a trace element and the body's tolerable upper intake level is only about 400mcg. That's equal to 4 raw brazil nuts, and anything more can give you selenium poisoning. The symptoms of mild selenium poisoning are hair loss, fatigue, neurological damage, gastrointestinal disorders, and garlic breath. Higher levels of selenium poisoning can result int liver cirrhosis, plumonary edema and even death. So don't ever binge on Brazil Nuts.
3. Peanuts / peanut butter. Peanuts that are not properly stored can grow a species of fungus (mold) called Aspergillus. As this fungus grows, it produces a type of molecule known as Aflatoxins. Aflatoxins can cause severe damage to the liver, and are highly carcinogenic. So throw out any moldy peanut butter or peanuts. You could be saving your own life.
4. Soy beans. There is a lot of controversy around soy beans. Some scientists believe that it is harmful to human health, while others believe it has many health benefits. But one thing is clear about raw soybeans: they contain high levels of protease inhibitors (a type of molecule). These molecules inhibit the action of proteases, which are enzymes that occur naturally in the human body. Proteases help the body digest food, among other things. Some of the protease inhibitors in soy beans can be deactivated by cooking over a high heat: 120 minutes at 140C/280F, or 30 minutes at 160C/320F. At the very least, bring soybeans to a rolling boil for at least 10 minutes before using them. Otherwise you might find yourself with a bad case of indigestion.
5. Kidney Beans / White Beans / Green Beans / Broad Beans / Fava Beans. When raw, these beans have a high levels of a molecule known as phytogaemagglutinin. As few as 5 raw kidney beans can cause poisoning, the symptoms being nausea, vomitting and diarrhea. Cooking the beans at 100C (boiling water) for at least 10 minutes can make the beans safe to eat by reducing the amount of phytogaemagglutinin up to 200-fold. But if you only cook them at 80C, you actually increase the amount phytogaemagglutinin tremendously, making the beans extremely toxic. The best thing to do is to soak these beans in water and bring them to a rolling boil for at least 10 minutes. Then you can use them in your recipes, or put them into a slow cooker for simmering.
6. Fruit Pits (Apricot kernels, Apple seeds, Almond, Cherry seeds, plums, peachesetc), Almonds, Lima Beans. They have a type of molecule called cyanogenic glycosides, which has a cyanide compound embedded in it. Ordinarily the cyanide is not released, so it is not dangerous. But when cyanogenic glycoside molecules come into contact with the beta-glucosidase enzyme which is found in the small intestine and some common foods, the cyanide is released and becomes dangerous. The amounts are small enough that you don't have to worry about in normal daily eating. But think twice if someone dares you to eat a pile of seeds.
7. Tapioca (Cassava, Yuca, Manioc). The raw leaves have cyanogenic glucosides and are poisonous. Tapioca roots can also have high levels of cyanogenic glucosides, and they must be processed correctly to reduce the levels of these cyanogenic glucosides to safe levels. This usually involves soaking the root for some time, then cooking it thoroughly. Don't prepare tapioca root at home unless you have professional advice.
8. Rhubarb Leaves. Rhubarb stalks are perfectly safe for use, but Rhubarb leaves are poisonous. They have oxalic acid and other toxic compounds. Eating a few kilograms of leaves could kill you, while smaller quantities can leave you seriously ill.
9. Tomato Leaves and Vines. The leaves and vines of the tomato plant are poisonous. You won't find them in stores, but be careful of them if you grow tomato plants in your garden.
10. Grapefruit and Starfuit. Both these fruits interfere with many modern medicines, and increase the potency of medicines in the body. This is potentially fatal because a usually safe dosage of medicine could suddenly have two or three times its normal potency if you eat one of these fruits. This can result in a fatal overdose of medicine. Starfruit also has oxalic acid, which can be fatal for patients with kidney diseases. Beware of starfruit juice and grapefruit juice, because it typically takes a lot of fruit to make one glass of juice, which means that a single glass of juice is the equivalent of eating a whole lot of these fruits.
Here is an interesting link on the effect of heat on foods.
Article Copyright © 2008: Wei L. Wang (Image credit: Fir0002)