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Is raw food more nutritious?

Are we harming ourselves by cooking all of the goodness out of fresh foodstuffs? Dr Karl has been stirring the pot and he's here to serve up the results.

A chef with a basket of raw fruit and vegetables

A chef with a basket of raw fruit and vegetables (Source: Gary Cameron/Reuters)

According to the rock musician Frank Zappa, the only things you can't have too much of are sex and vegetables. He was a great musician, but maybe slightly lacking as a nutritionist. It turns out that eating only uncooked non-meaty food is too much of a good thing.

The raw food movement probably began with Sylvester Graham in 1850. He was a Presbyterian minister and promoter of dietary reform, who started the American Vegetarian Society. Vegetarians eat no meat, including fish and poultry.

The next stage along are the vegans. Vegans are vegetarians who eat neither dairy nor eggs — in fact no animal products at all — but who can usually get a belly-full of fruit, nuts, seeds, grain, cereals, berries, beans and sprouts.

And the next stage after that are the raw-food advocates. They are usually vegans who often have only one type of food at each meal, and who do not cook their food.

The raw food movement sputtered along in the 20th century. It was helped by a few people. They included the American scientist, E. B. Forbes. In 1933, he aired his dislike of both cooked food and houses with glass windows. In 1936, the American dentist Weston A. Price, blamed cooked food for many dental problems.

And of course, there was the Chicago medical doctor, Edward Howell, who wrote a book called The Status of Food Enzymes in Digestion and Metabolism. Today, there are a few raw-food restaurants in California, New York and Germany.

There are a few theories underlying the raw food movement.

One theory badly mangles the principles of thermodynamics and entropy to blandly claim that the energy in "living foods" is "of the highest order", and therefore is "most beneficial to health".

In another theory, Howell wrongly claimed that each of the foods we eat contain natural enzymes to digest that food, that the heat of cooking destroyed these enzymes, and therefore cooking foods made them harder to digest.

The theories all claim that cooking strips fruit and vegetables of their vital nutrients, and makes them harder for our bodies to metabolise, so that cooked foods are supposedly less healthy than raw foods.

But when you look at the nutritional science of it all, you get a different story. In fact, heating foods normally makes their nutrients more easily digestible. It does this in several ways. These include: breaking down the physical barriers in the food, for example, husk and thick skin; bursting open the cells so that the contents are more available; modifying the molecules; breaking down large indigestible molecules into smaller digestible molecules; and finally, breaking down toxins or chemicals in the food.

Yes, cooking vegetables does reduce their vitamin C a bit, but not to zero, and you do get vitamin C from fruit. One study showed that if you cooked vegetables, you would actually increase their antioxidant activity. We're not sure why, but probably the heat-softened the veges, and made their antioxidant chemicals more accessible to our digestive system.

Studies done on raw foodists show that they are generally undernourished. They have reduced bone mass (with bad implications for osteoporosis later in life), and reduced levels of good chemicals, such as vitamin B12, iron and vitamin D. And even though they eat more carotenoids (from yellow fruit and veges) than the rest of us, they have lower levels of vitamin A, because they seem to be poor converters of carotenoids to vitamin A.

The raw foodists claim that eating raw food has long been the "natural" way for us to eat our food. But we have archaeological evidence of humans cooking food some 700,000 years ago.

And finally, about half of the women who follow the raw food diet get so malnourished that they stop having periods. So if a raw-food diet makes women infertile, and if raw food was how we used to eat food, then how did the human race multiply so successfully? Surely baby-making should outrank a raw-food diet in terms of doing what comes naturally. It seems that with both food and baby-making, some like it hot...

Tags: health, diet-and-nutrition, vitamins, food-and-cooking, food-processing

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Published 29 April 2008

© 2019 Karl S. Kruszelnicki Pty Ltd