Raw foods diets: a review of the literature.
IT IS WELL ESTABLISHED that vegetarian lifestyles are associated with health advantages. The American Dietetic Association states that "... appropriately planned vegetarian diets are healthful, are nutritionally adequate, and provide health benefits in the treatment and prevention of certain diseases."
Much of what is known about vegetarian diets and related health effects is based on research on lacto-ovo-vegetarian diets. However, relatively little information is available about the health and nutrition aspects of vegan diets, as well as variants such as raw foods or living foods diets. A review of the literature was conducted to determine the extent to which there is scientific documentation of the health and nutritional aspects of raw foods diets, as a first step toward further study of this dietary practice.
Worldwide, little research data are available on the subject of raw foods diets. The majority of published research has been conducted in Finland at the University of Kuopio. Of the 24 papers included in this review, 15 originated in Finland. The remainder of the research was conducted in the US, the Netherlands, and Germany.
Raw foods diets are variously described as uncooked vegan diets, uncooked vegetable diets, or "living foods" diets. In one case, a raw foods diet included raw liver. All of the other studies reviewed here referred to vegetarian diets, most of which excluded all animal products and derived the majority of calories from uncooked plant matter. In one study, up to 95 percent of food was consumed in raw form. One study group derived 55 percent of calories from uncooked fruits and vegetables, carrot juice, salads containing raw vegetables, and grain products, though 58 percent of subjects also consumed some animal product during the recorded week of food intake. In other studies, a "living foods" diet was defined as an uncooked vegan diet that included germinated seeds, sprouts, cereals, vegetables, fruits, berries, and nuts.
The scientific literature contains relatively little information about the rationale for a raw foods or living foods diet. One paper provides a philosophical discussion that examines food energy and its role in sustaining optimal health. Other papers focus on specific health effects on adult subjects following a raw foods or living foods diet for a period of time ranging from as little as one week to as long as 3.7 years. Study groups ranged in size from as small as 13 subjects to as many as 513 subjects. Findings include dietary effects on weight, serum lipid levels, symptoms of rheumatoid arthritis and fibromyalgia (a condition that is associated with all-over aching, stiffness, and fatigue of the muscles and soft tissues), rates of dental erosion, fecal microflora, cancer treatment, vitamin [B.sub.12] status, and antioxidant and other nutrient intakes.
Four studies found uncooked vegan ("living foods") diets to be associated with substantial loss of weight. In one case, weight loss was associated with reduction of diastolic blood pressure, in one case reduction of fibromyalgia symptoms, and with amenorrhea (the absence of menstruation for at least three months in a woman who has previously menstruated) in another case. Other studies found subjective improvement of fibromyalgia and rheumatoid arthritis symptoms with the adoption of an uncooked vegan diet.
An uncooked vegan diet was associated with decreased serum total and LDL-cholesterol levels. Another study found that long-term uncooked vegan diets resulted in decreased levels of N-3 (Omega-3) fatty acids due to high intakes of linoleic and oleic acids. Two studies found significant reductions of serum vitamin [B.sub.12] concentrations in subjects following a raw foods ("living foods") diet, suggesting that long-term adherents to a raw vegan diet should include a reliable source of vitamin [B.sub.12] in their diets.
Other studies focused on favorable effects of an uncooked vegan diet on fecal microflora and other potential chemopreventive factors for cancer risk. One study found overall favorable changes in biochemical and metabolic health indicators, including serum protein, urea, and total cholesterol in subjects eating a raw foods diet for one week, but concluded that observation over a longer period was needed. One study found increased risk of dental erosion in subjects following an uncooked vegan diet. Another study examined coumarin 7-hydroxylation (the enzymatic conversion of plant substances into products that are soluble and can be excreted by the body) in subjects consuming a raw foods vegan diet matched with omnivorous controls, and concluded that plant substances had little effect on coumarin hydroxylase activity in subjects consuming a raw foods diet.
Finally, one study of 141 American long-term (mean time 28 months) adherents to a raw foods diet found self-reported improvements in health and quality of life after adoption of the diet. This measurement was based on survey results of each subject's current health and retrospectively of health prior to the dietary changes. The study found that salads, fruits, carrot juice, and cooked grain products provided 60-88% of most of the nutrients found in the diet. Dehydrated barley grass juice, nuts and seeds, potatoes, and squash provided the remaining 12-40%. The diet provided an average calorie intake of 1460 KCAL/day for women and 1830 KCAL/day for men. Fat provided 24% of calories, and average protein intake was 0.66 g/kg body weight. Mean calcium intakes were 580 mg/day for women and 690 mg/day for men. As compared to mean nutrient intakes of people in the United States, as reported in the National Health and Nutrition Examination Survey (NHANES III), intakes of several nutrients were significantly higher in subjects eating a raw foods diet, and intakes of several nutrients were lower. Intakes of fiber, vitamins A, [B.sub.6], C, and E, folate, copper, and potassium were significantly higher in subjects eating a raw foods diet as compared with those reported in NHANES III, and intakes of protein, total and saturated fat, cholesterol, vitamin [B.sub.12], phosphorus, sodium, and zinc were significantly lower.
Overall, the body of scientific literature describing health and nutrition aspects of raw foods or living foods diets is limited. Only one survey of American individuals consuming a raw foods diet has been reported. Little or no information is available describing the rationale for a raw foods diet, nor has the range of practices among individuals consuming raw or living foods diets been documented. The majority of available research findings related to raw foods diets is confined to studies of European populations.
Suzanne Havala Hobbs is a Registered Dietitian with a doctorate in public health policy and administration. She serves as nutrition policy advisor for The VRG and is an adjunct assistant professor in the Department of Health Policy and Administration, School of Public Health, The University of North Carolina at Chapel Hill.
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|Author:||Hobbs, Suzanne Havala|
|Date:||Jul 1, 2002|
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