The raw food diet craze
The belief in the benefits of raw foods—sometimes called “living foods”—is nothing new. Sylvester Graham, for whom the cracker is named, promoted raw foods 150 years ago, just as some chefs, cookbooks, celebrities, and websites promote them today. Among other claims, raw food diets are said to eliminate headaches and allergies, improve memory and immunity, ease arthritis, and reverse diabetes. Proponents say that cooking destroys nutrients, enzymes, and the “life force” of the food itself.
A raw food diet is based mostly or exclusively on uncooked and unprocessed plant foods, including fruits, vegetables, nuts, seeds, and sprouted grains. Most followers are strict vegetarians, though some eat unpasteurized dairy foods and sometimes even raw eggs, meat, and fish. Foods are prepared using blenders, processors, and dehydrators, and can be served either cold or warm, but not hot enough to cook them. Truly dedicated raw foodists shun refined sugar, vinegar, coffee, tea, soy products, most vegetable oils, dried herbs, and alcohol.
Raw food diets encourage people to eat lots of fresh produce, nuts, seeds, and other nutritious foods that contain little or no saturated fat, cholesterol, and sodium and are high in fiber. Though research comparing raw food diets to other eating patterns is limited, they have been linked to lower LDL (“bad”) cholesterol, triglycerides, and body weight. In one observational study from Roswell Park Cancer Institute in Buffalo, people who ate the most raw (as compared to cooked) cruciferous vegetables had a reduced risk of bladder cancer, possibly because the raw vegetables retain more cancer-protective isothiocyanates. Cooking, after all, does reduce some phytochemicals, including isothiocyanates, as well as many vitamins.
Some nutrients and potentially beneficial plant compounds are less available to the body in the raw state. Heat is needed to break down a plant’s cell walls and release the compounds. Cooking a carrot releases extra beta carotene, while cooking tomatoes releases more lycopene.
Of more concern, some uncooked and unpasteurized foods pose a risk of food poisoning, which is especially dangerous for pregnant women, young children, the elderly, people with compromised immunity, and those with chronic medical conditions, such as liver or kidney disease. Raw sprouts, raw oysters, and raw (unpasteurized) milk products have been the cause of many outbreaks of foodborne illness in recent years. Heat, in cooking and in pasteurization, kills pathogens. Depending on how strict the diet is, people on raw food diets may also need to take supplements to make up for potential shortfalls in calcium, iron, zinc, vitamin B12, and other nutrients.
What about the enzyme argument?
Raw foodists claim that the enzymes in raw foods (destroyed by cooking) aid digestion, prevent “toxicity” in the body, and have other curative effects. But these enzymes are there for the plants, not us. Moreover, they are largely inactivated by the highly acidic environment of the stomach and thus cannot aid digestion farther down in the intestines or have other benefits. And there’s no evidence that the enzymes can become reactivated in the intestines, as some raw foodists say. In any case, even if some enzymes do survive, the body usually makes all the enzymes it needs to digest and absorb food. The claim by some raw foodists that our bodies have a limited lifetime supply of enzymes makes no sense, either, and is simply not true.
Cooking, the mother of inventions
The invention of cooking was a crucial factor in the evolution of humans. Cooking, which distinguishes us from other species, makes high-protein foods softer and easier to digest, and this enabled our early ancestors to devote more energy to other activities besides hunting, gathering, and chewing raw foods all day. Besides killing bacteria and releasing healthful compounds from cell walls, cooking also allows us to more easily consume pasta, rice, wheat, corn, and potatoes.
A matter of balance
Raw fruits, vegetables, nuts, and seeds are certainly good for you. But you don’t need to—and should not—restrict yourself to raw foods only. There’s no conclusive evidence that a pure raw food diet will prevent or cure any condition or disease. Plus, it’s an extreme diet that’s hard to maintain over the long run, deprives you of some of the tastiest and most nutritious foods (like cooked beans, sweet potatoes, and most whole grains), makes dining out difficult, and can be deficient in some nutrients.