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It will appear that heating does not destroy all of these constituents, and that some (but not all) of the toxins listed below are found in foods that are commonly eaten cooked, but that are inedible raw, except perhaps in small quantities (like potatoes). Thus a good argument in favor of eating raw is that you reduce your exposure to many natural toxins.
"Avoiding toxins" does not solve the nutritional cost/
"Alien" proteins vs. cooked forms of proteins. Finally, we notice that with the Paleolithic diet, which is not an all-raw diet, foods that are not edible raw are avoided but for different reasons than toxicity per se. From the Paleolithic diet point of view, it is more important to avoid "alien" proteins that cause problems via molecular mimicry (i.e., autoimmune reactions) than to avoid cooked forms of proteins we are adapted to. In this view, it is more a consideration that foods requiring processing were ones that were introduced relatively late in human history, so that genetic adaptation to them is not yet complete, irrespective of any cooking/
Considering the practicalities. Remark: We do not recommend worrying excessively about completely avoiding (all of) the foods listed below, first of all because the list is not exhaustive and toxins are quite widespread in nature. And secondly because our body has many detoxification mechanisms which are specifically designed to allow it to handle moderate, relatively normal amounts of toxins without deleterious consequences. Our goal, rather, is to show that one needn't be excessively concerned about potential harmful effects of the chemical constituents created by cooking, since all living animals are naturally exposed to quite a variety of toxins in the foods they eat anyway.
Fava beans. The well-
Soybeans. From Liener [1994], soybeans contain some heat-
Concerning poisonous mushrooms, obviously cooking amanitas (an extremely poisonous variety of mushroom) won't make them edible, but there are examples of mushrooms which become edible after cooking. Since these varieties are very special and can't be found at the grocery, we won't expand further.
Because of the large number of compounds in this class, generalizations about the function of flavonoids are difficult [McClure 1975]. However, the following can be said about certain flavonoids:
Note here that the monkeys were fed semi-
In tests feeding high-
Role of oxidized LDL cholesterol in atherogenesis. O'Keefe et al. [1995, pp. 70, 72] explain the role of oxidized cholesterol in atherogenesis as follows:
The oxidative modification of LDL cholesterol seems to be the final common pathway in the process of atherosclerosis.
Here it should be noted that some aspects of the effects of oxidized cholesterol are controversial in the sense that a scientific consensus has not yet been reached. Readers are encouraged to consult O'Keefe et al. [1995] and Steinberg et al. [1989] for a detailed overview of current knowledge in this field.
The paradox of relatively high cholesterol intake and cooked meats vs. rarity of heart disease in hunter-
This divergence may be due to the differences between the type of meat (wild game) in hunter-
Viewing single factors out of context can be misleading. Thus if cholesterol and/or oxidized cholesterol are in fact atherosclerotic in effect, then the implication is that there must be something else in the diets/
The general point here is to keep in mind that, before attempting to form conclusions that might be premature, it is important to view the role of any one factor in the equation of health in the context of the overall diet rather than in isolation. Depending on the situation, the benefits of a food or class of foods may mean more for the health of the body than whatever associated negatives there may be--
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From Marth [1990], mycotoxins (toxins produced by molds) are completely destroyed at their melting point, which is generally at high temperatures: 164°C (327°F) for Zearalenone, 170°C (338°F) for Rubratoxia. When roasting peanuts, the toxicity of aflatoxin B1 is reduced by 70%, and that of aflatoxin B2 by 45%. Thus, heat treatment cannot be considered as a satisfactory means to eliminate mycotoxins.
Raw kidney beans at a level as low as 1% of diet can cause death in rats in two weeks. Beans cooked at 100°C (212°F) for 30 minutes, and incorporated at a level as high as 20% of diet, do not retard growth when tested against casein. (Feeding rats with casein instead of beans doesn't affect their growth rate, and can therefore be used as a baseline for comparison.) However, when beans which have been cooked at the lesser temperature of 70°C (158°F) for 30 minutes are incorporated, growth retardation is almost as great as that which occurs when raw beans are fed. The small amount of lectin present in beans cooked at 70°C might be responsible for this effect [McPherson 1990]. However, cooking kidney beans doesn't destroy all antinutrients [Grant et al. 1982].
From Faldet [1992], heat treatment of soybeans destroys or reduces heat-
The antinutrients here (anti-
Raw egg white contains a protein called "conalbumin" which binds to iron. Additionally, raw egg white contains avidin, which binds to biotin and can impair metabolism of other B-vitamins. Note however that raw egg toxicity should not be overstated: 20 raw eggs per day for several weeks would be necessary to create a biotin deficiency.
The most common commercial mushroom, Agaricus bisporus, causes cancer in mice [Toth 1986]. The dosages required were almost half of their total food intake.
Potatoes contain solanine and chaconine, which are not hazardous unless large quantities are eaten. They don't accumulate in the body, and are not destroyed by heat.
These contain oxalates, which among other effects inhibit calcium absorption. Again, they are not hazardous unless large quantities are eaten. They don't accumulate in the body, and are not destroyed by heat.
These are found in lima beans, cassava, and many fruit pits [Beier et al. 1994]. Processing techniques partially destroy cyanogenic glycosides, but some poisonings caused by the consumption of large amounts of cassava or fruit pits have been reported, including apricot kernels. When in contact with stomach acids, the cyanogenic glycosides release cyanide, which is the active component in Zyklon B (used by the Nazis in death camps). So indeed cyanide is toxic in large amounts, but obviously a few apricot kernels will not do much harm.
Contains some trypsin inhibitors and lectins, which are destroyed by heat [Seo 1990].
These contain toxic psoralens, which are potent light-
[C]onsumption of moderate quantities of this vegetable by man can result in the intake of appreciable amounts of psoralens. Consumption of 0.1 kg of parsnip root could expose an individual to 4 to 5 mg of total psoralens, an amount that might be expected to cause some physiological effects under certain circumstances...
Flavonoids are a broad class of compounds common in plants and in the human diet. The basic characteristic of flavonoids is that their chemical structure includes what is known as the flavonoid skeleton, that is, a skeleton (core) of diphenylpyrans, i.e., C6-C3-C6, where the C stands for carbon, and C6 is a benzene ring [Hertog and Katan 1998]. Over 4,000 flavonoids are known, and new ones are being researched and described [Hollman 1997]. In plants, flavonoids serve a number of functions: as pigments (the color of fruits and flowers is due to flavonoids), antioxidants, sunscreens, etc.
Alfalfa sprouts contain approximately 1.5% canavanine, a substance which, when fed to monkeys, causes a severe lupus erythematosus-
Let's mention quickly a few other examples: pyrrolizidine alkaloids, present in herbal teas, are carcinogenic, mutagenic, and teratogenic (cause birth defects); gossypol in cottonseed causes abnormal sperm and male sterility, and is a carcinogen; piperine in black pepper causes tumors in mice; capsaicin in hot pepper is a mutagen; allyl iosthiocyanate, in oil of mustard and horseradish, is a carcinogen in rats; quinones and their phenol precursors (in many different plants) have mutagenic and antimutagenic properties.
Other toxic effects of cooking
It is possible that heated milk protein may be a factor in atherosclerosis [Annand 1971, 1972, 1986].
Oxidized fats, oils, and cholesterol. Research reveals that in animal models, oxidized fats, oils, and cholesterol induce higher levels of arterial plaque (i.e., atherogenesis) than do the corresponding non-
LDL cholesterol must be oxidized or glycosylated (or both) before it becomes atherogenic.(8,9) Oxidative modification of cholesterol occurs by means of oxygen free radical processes. Only after the LDL has been modified (through oxidation or glycosylation) does it activate differentiation and migration of macrophages. The scavenger receptors on the macrophages recognize oxidized LDL (but not unmodified LDL) and allow for subsequent phagocytosis. When the macrophage becomes filled with oxidized LDL cholesterol, it becomes the foam cell that is typically observed in early atherosclerotic lesions...
Steinberg et al. [1989] also report that oxidized LDL cholesterol, at high levels, is atherogenic. For a good summary of the atherogenic properties of oxidized LDL cholesterol, see Table 2 in O'Keefe et al. [1995, p. 72], and Table 1 in Steinberg et al. [1989, p. 917].
(Lesson of the Pottenger's Cats Experiment: Cats Are Not Humans)
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