The growing interest in vegetarianism -- driven by health and environmental concerns -- has spawned an offshoot known as the raw foods movement.
Those who aim to consume "living foods" do their best to eat foods as quickly as possible after harvest. Devotees say that beneficial components in plants -- variously referred to as enzymes, energy or even a life force -- are destroyed when foods are heated above a temperature of about 118 degrees.
The number of raw foodists in the U.S. is unknown, and very little research exists documenting their eating habits. In one report, interviews with 17 leaders in the movement indicated they had followed their diets for an average of 13 years, and most consumed a diet consisting of at least 85% raw foods.
They cited health as the primary driver in adopting the diet as well as a number of perceived advantages, including disease prevention, faster healing, weight control, better digestion, more energy and a greater connection with nature.
Research has yet to prove whether raw food can provide all of these benefits, but the diets have some potential shortcomings.
A raw vegan food plan may lack adequate protein and calcium and is likely to be deficient in vitamin B12. A compound found naturally only in animal foods, vitamin B12 protects nerve fibers and genetic material. In a recent study of 201 raw foodists in the Netherlands, published in the Journal of Nutrition, 38% were vitamin B12 deficient, and more than half had elevated blood levels of homocysteine, an amino acid that requires vitamin B12 for processing and that, when elevated, increases heart disease risk.
A diet rich in raw plant matter is bulky, filling and low in calories, so it is not surprising that the adoption of a living foods diet is associated with a substantial loss of weight. In one of the largest studies of long-term raw foodists in Germany, published in the Annals of Nutrition & Metabolism in 1999, 25% of women and nearly 15% of men were underweight. Among women of childbearing age, 30% had disruptions or cessation of their menstrual cycles -- likely related to loss of weight and body fat.
It should be noted that the plant enzymes that raw foodists attempt to preserve are no match for the highly acidic environment of the stomach. There, they're rendered inactive before digestion is complete. And some phytonutrients, such as the brightly colored carotenoids found in tomatoes, spinach and carrots, are not as readily absorbed from raw foods as they are from cooked foods. Similarly, the magnesium, calcium, iron and zinc naturally present in whole grains are released more thoroughly during cooking.
Anthropologists Richard Wrangham and Nancy Lou Conklin-Brittain of Harvard University say humans were meant to consume cooked foods. Heating foods renders them more digestible -- allowing better absorption of much-needed calories.
They point out that humans have cooked foods for more than 250,000 years, a time period long enough to produce biological adaptations -- smaller teeth, longer small intestines and smaller colons than our ancestors -- in response to eating a cooked-food diet.
Graham never got other food reformers of his time to rally behind him, but perhaps the resurgence in interest will generate much-needed research on the effects of a living foods diet.
Susan Bowerman is a registered dietitian and assistant director of the UCLA Center for Human Nutrition.