For raw-food fanatics, it's not a matter of whether raw is good - there's no punch to that line. The extremists making the media headlines vilify cooking. This forces a situation where cooking has to be bad or the raw foodist position isn't special.
One of the key arguments for the raw-food diet is that cooking destroys the enzymes in food and we need the enzymes to aid digestion. Living cells house membrane-bound packages of enzymes called lysosomes. They serve the purpose recycling nutrients and effecting self-digestion in older proteins. This self-digestion, called "autophagy" goes on continually throughout life. It's part of cell remodeling and is enhanced during stress, such as the stress from starvation.
When an organism dies, the lysosomes break, releasing the enzymes which digest protein in their vicinity. Thus the enzymes in food are not necessarily critical to digestion.
Yogurt is more digestible to many people because the protein is "predigested" by bacteria. Does that mean all foods should go through bacterial degradation before they're fit for consumption? We still have to use our own digestive enzymes to process the proteins, fats, and carbohydrates in raw food into the forms we can absorb.
In an attempt to get around these problems, raw foodists have an escape clause: They are "allowed" to make many preparations of soaked grains and legumes that are heated to just below the temperature at which enzymes are supposed to be destroyed. But methods such as this or other tricks, such as dehydrating, have yet to be put to solid scientific testing.
Some foods are only able to be properly digested when cooked. Legumes contain an inhibitor that counters trypsin, a protein-digesting enzyme in the small intestines. Heating destroys that inhibitor and thus increases the protein quality of the legumes. Legumes also contain phytic acid, which can bind minerals and make them less available. There are many ways to stop the actions of phytic acid: soaking, germination, fermentation and cooking.
Also, only cooking has the added advantage of gelatinizing the starch, which makes it more digestible. We obtain far more energy from starches (grains, beans, and potatoes) when they're heated and allowed to gelatinize.
The inability to fully access the calories in starch makes it difficult for raw foodists to hold body weight and strength. That's one reason for the weight loss in an all-raw diet. A "raw only" eater is also at risk for muscle loss, because it's difficult to store muscle glycogen effectively on such a diet.
Another myth of raw fanatics is that we are born with a certain amount of enzymes, and if we waste them on digestion, we don't have enough to carry on metabolism. This is utterly off base. Enzymes are highly specific protein molecules that perform equally specific tasks and are created as needed by the body.
We aren't bequeathed a limited number at birth any more than we are bestowed a ration of antibodies to fight infection. Enzymes aren't in limited supply unless there's an underlying nutrient deficiency, or genetic abnormality. We need vital materials from diet to build enzymes, just as we need vital materials to build any protein. True, many of these vital materials are found in abundance in raw food, but many are found in properly cooked food as well.
The fact that every reaction in the body is made possible because enzymes lower the "energy of activation" is not an argument for the necessity of eating them intact. Enzymes in foods are proteins and are digested the same as any other food protein - they're broken down into constituent amino acids.
For an enzyme in food to act as functional molecule in our body, it would have to routinely escape our digestive enzymes, and enter the blood as an intact protein. Then it would have to fool the immune system into thinking that this is not really a foreign protein, but a friendly nutrient. Otherwise we'd be in for a severe allergic reaction if not all-out anaphylactic shock resulting in physical collapse or even death.
Even if intact "live" enzymes acted as essential nutrients - which they can't - it's still only an argument for eating raw food, not for avoiding cooked food.
There are a few possible risks with an all-cooked diet. Raw foodists fear that cooking destroys vitamins. Well, that's true. Water-soluble vitamins, such as vitamin C, are destroyed in the cooking process. Not completely, but certainly enough to make a significant impact. Sailors of the Renaissance times found this out when they developed scurvy on long voyages. Solution? Eat some fresh fruit-problem solved. The fact that most Americans eat a highly processed diet very low in fresh fruits and vegetables is not an argument for restricting the diet by rejecting cooking.
The case for deficiencies
The usual argument against the all-raw diet is that there are risks for deficiencies, particularly calcium, iron, and B12. Part of the reason is that raw foodists are often vegans who have added yet another restriction to their already limited diets.
The risk of deficiency is present with any restricted diet, especially the modern fast-food diet. That's why "variety, balance, and moderation" is not merely a cliché but a solid nutritional defense strategy. Certainly; there are supplements to shore up any diet that creates a deficiency. But the real issue of raw food, the one that draws all the attention, implies all cooked food is bad.
Some raw foodists insist that at least 75 percent of the diet should be raw. And that's not an argument for a raw-food diet. It's an argument for the benefit of raw food in the diet, about which there is no debate. But if 25 percent of your diet is cooked, you're not a raw foodist, just somebody who likes raw food. If 25 percent of my diet is meat, am I a vegetarian?
The truly extreme raw foodists claim that cooking is unnatural, that no other animal cooks its food, only humans. Yet even by the most conservative estimates, cooking began at the very latest 300,000 years ago (with estimates on the other end going back to nearly one million years ago). Homo erectus, an ancestral cousin whose brain was about three-fourths the size of modern humans, was the dominant hominid then. Neanderthal, the large-brained hominid that emerged in Europe around 190,000 years ago (and is considered the quintessential "cave man") was cooking food. Homo sapiens (our species) didn't arrive until the earliest about 150,000 years ago in Africa.
In other words, cooking predates anatomically modern humans. There was no such thing as a natural, all-raw Homo sapien or any all raw food-eating large-brained hominid for that matter. How unnatural is cooking if we must go back to doll-sized monkeys swinging in trees to find a time when cooking wasn't routine?
Raw food is great and, I would argue, an irreplaceable part of a healthy diet. Raw food cookbooks offer some fun, interesting and innovative ways to introduce a large variety of healthful raw foods into the diet. But when the discussion changes from the benefits of raw food to the evils of cooking, we've left promoting health far behind and ventured into the shaky realm of selling a pseudo philosophy.