You may have seen the headlines on the Web sites: “Cooking kills! Live longer and stronger with living foods.” You may wonder: are some foods alive? Is this the latest nutrition breakthrough or just the latest unfounded fad? As with many questions in nutrition, the “either-or” approach doesn’t give the whole answer.
The Fiction and the Fact
The raw foods, or “living foods,” diet includes only fresh, unprocessed plant products, prepared using temperatures below 116°F. Ideally, they are organically grown. Supporters claim this way of eating is the most healthful and most natural. Cooking destroys not only nutrients, they say, but also enzymes in the food that are needed to digest those nutrients fully. Advocates point out that people ate raw fruits, vegetables, nuts, and seeds long before they learned to cook. They say that a return to this original diet increases energy, strengthens immunity to disease, and improves mental health.
It’s true that cooking destroys essential enzymes—essential to the food, that is. The human digestive tract itself contains the enzymes needed for digestion. A greater problem is that moderate heat actually activates some enzymes, allowing them to start destroying delicate nutrients like vitamin C. That’s why you’re advised to have water already boiling before adding food to cook: the higher temperature kills the enzyme before it can attack the nutrients.
It’s also true that humans have subsisted almost entirely on plant products for most of their existence. There’s no way to tell how healthy early humans were, however, or how much of that health was due to their physically active life.
What about the claim that cooking destroys nutrients? Applying heat can reduce nutritional values, especially in delicate fruits with sensitive vitamins. In some cases, however, it has the opposite effect. In fact, some researchers believe that if people had not learned to cook some 500,000 years ago, they might not have learned much else since then. How is this so?
Opening the Door to the Nutrient Store
Cooking can increase the amount of a nutrient that can be digested and absorbed, or its bioavailabilty. Carbohydrates, or starches, are a good example. You’ll recall that heat and water break down starch molecules in a process called gelatinization. Without this process, cereal grains and many root vegetables would be less enjoyable. Dry beans and peas would be inedible. Many types of beans benefit from cooking in other ways. The heat kills certain enzymes that prevent the intestine from absorbing the bean’s nutrients. Lima beans contain the poison cyanide, which is released harmlessly as a gas during cooking.
Thus, cooking added three major sources of carbohydrates to the human diet. Carbohydrates are literally brain food. Without them, scientists say, human intelligence would not have grown as it did.
Other nutrient profiles get a boost from cooking too. Corn contains niacin and lysine, an essential amino acid, but in forms that humans cannot use. In cultures where corn is a staple, people learned that boiling it in water mixed with wood ash or burnt shells made it easier to grind for recipes—to make corn flour for tortillas, for instance. Food grade lime replaces wood and shells today, but the effect is the same. The lime reacts chemically with the niacin and lysine molecules, changing then into a digestible form.
Finally, consider beta-carotene. Steaming or roasting carrots and squash breaks down their sturdy cell walls, releasing more of their rich supply of this phytochemical.
Of course, uncooked foods still play an important role in good health. The living foods diet may be only a fad, but the ancient wisdom of snacking on an apple or a handful of raisins still applies today.
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