Thursday, 6 December 2012

Is Cooked Food Toxic?

In the raw food movement, there are three main arguments for why you should eat a raw food diet. They are as follows:
  1. We haven't been cooking very long
  2. Cooking creates toxins, and carcinogens
  3. Cooking destroys nutrients

How long have we been cooking?

In his book “The 80/10/10 Diet”, Douglas Graham states we've likely only been cooking regularly for 10, 000 years. He states it takes around 50, 000 to 500, 000 years for evolutionary change to occur.

There's a lot of agreement among anthropologists that human ancestors were cooking their food as long ago as 250,000 to 500,000 years, but Richard Wrangham and a few of his colleagues see evidence that cooks spoiled the broth as long ago as 2 million years. That's about the time when our ancestors became less like apes and more like humans [1].

Italian wall lizards introduced to a tiny island off the coast of Croatia are evolving in ways that would normally take millions of years to play out. In just a few decades the 5-inch-long lizards have developed a completely new gut structure, larger heads, and a harder bite [2]. Exceptions don't make the rule of course, but consider that we could also be an exception and that it is uncertain how long adaptations take if they even need to occur.

If we had only been cooking consistently for 10, 000 years, we would have reason to suspect we may not be adapted to it, but it wouldn't prove anything. We need studies showing the negative effects of cooking.

Does cooking really create toxins, or carcinogens?

Many of the people promoting raw food diets say cooking creates toxins, often without mentioning what toxins, or giving any real proof. The following are all the potential, or proven, toxins I'm aware of that are created, or elevated, by cooking.


Acrylamide is known to cause cancer in animals. Also, certain doses of acrylamide are toxic to the nervous system of both animals and humans. Acrylamide is formed by frying, baking and grilling. Acrylamide has not yet been found in foods cooked below 120 degrees Celsius.[3] If it were found, levels would be very low. High intakes have been linked to certain cancers [4].

HCAs and PAHs

Exposure to high levels of Heterocyclic amines (HCAs)and Polycyclic aromatic hydrocarbons (PAHs)can cause cancer in animals; however, whether such exposure causes cancer in humans is unclear. Benzanthracene, benzofluoranthene, benzopyrene, dibenzanthracene, and indenopyrene are examples of PAHs. HCAs and PAHs are formed when muscle meat, including beef, pork, fish, and poultry, is cooked using high-temperature methods, such as pan frying or grilling directly over an open flame [5].


Nitrosamines have been proven carcinogenic in many species. They are probably carcinogenic to humans too [6]. Nitrosamines are made from nitrates. Nitrates are found in some vegetables, but Nitrosamines are not. They are mostly found in meat and dairy [7][8].


Small amounts of acrolein may be found in some foods, such as fried foods, cooking oils, and roasted coffee [9]. The Department of Health and Human Services (DHHS) has not classified acrolein as to its carcinogenicity. The International Agency for Research on Cancer (IARC) has determined that acrolein is not classifiable as to carcinogenicity in humans. The EPA has stated that the potential carcinogenicity of acrolein cannot be determined based on an inadequate database [10].


Advanced Glycation End Product levels aren't significantly different in raw and cooked plant foods. Some cooked items have lower levels than some raw items even [11].

If you're avoiding animal products, as well as grilled, baked and fried foods you shouldn't be consuming any potential, or proven, toxins or carcinogens. Although it can be said that those things are likely harmful to health.

Cooking destroys nutrients

Whilst this is true, the important question is, is a diet containing a lot of cooked food deficient in nutrients? Are raw food diets always better than diets containing cooked food? Of course a diet containing mostly cooked could potentially be deficient in nutrients, just the same as with raw diets, but it isn't necessarily deficient.

Lets take Vitamin C. Raw foodists will often talk about how cooking destroys Vitamin C. This is true. Vitamin C is very heat sensitive. It's also very important. The RDA is 90mg. You may benefit from getting more than this, but this isn't important for now. How can we obtain the RDA? 2 raw oranges give you 155% of the RDA, 1 raw red pepper gives you 169%, and 200g of boiled broccoli gives you 144%. This isn't a difficult nutrient to get a lot of.

Many 80/10/10 dieters rely on the banana as a staple. There's a calorie dense cooked food that beats the banana for Vitamin C content. The banana contains about 10mg of Vitamin C [12]. A boiled potato contains about 17mg of Vitamin C [13]. Yes cooking destroys Vitamin C. The potato had 42mg before cooking [14].

What if we need more Vitamin C? Out of all raw food dieters, 80/10/10 dieters probably get the most. The most popular 80/10/10 site on the internet is The creator of the site pushes high calorie fruits like bananas and dates. According to the records, dates don't contain any Vitamin C. Bananas aren't bad for Vitamin C, but you could get the same amount of Vitamin C as a person eating 30 bananas by eating 5 oranges a day. So eating a raw food diet doesn't necessarily mean you're getting more Vitamin C.

Denatured protein

Some will claim denatured protein is toxic and/or unusable. I see no evidence for it being toxic. Denatured proteins are actually more digestible [15]. A study tested the protein digestibility of raw and cooked egg. The cooked (denatured)egg protein was absorbed 41% more [16]. When you denature a protein it loses it's secondary and tertiary structure [17]. It's primary structure remains in tact. This is the important one. Your stomach acid denatures protein also [18][19].

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