Although vegetarian diets are typically defined by the exclusion of meat and other flesh foods, a healthy vegetarian diet is one in which a variety and abundance of plant-based foods are primarily consumed. Animal products such as dairy and eggs may be selectively consumed in varying amounts or not at all. Plant foods include: grains, legumes (including soy foods), vegetables, fruits, nuts, seeds, plant oils, herbs and spices, and plant-based beverages. A variety of foods from all plant food groups consumed daily in adequate quantities will provide all of the recommended nutrients (except for vitamin B12), fiber, and other substances needed.
In the past, unrefined foods have been emphasized because they contained more vitamins and minerals. The food industry has effectively refined and processed foods to the point where some foods must be enriched or fortified in order to replace some of the lost nutrients. While these foods are part of most diets, lesser-refined plant foods provide additional micronutrients, fiber, and various antioxidants and phytochemicals. More and more is being discovered concerning the importance of these food substances to physiological function, as well as the amount and balance needed for optimal health.
Although vegetables, fruits, nuts, and legumes are often consumed with minimal refinement, this is not the case for foods made from grains. However, whole-grain foods are more likely to decrease risk of heart disease, some cancers, and diabetes, while refined-grain foods do not appear to carry these same benefits. A diet based on unrefined and minimally processed foods is more likely to supply the quantities and proportions of substances deemed safe and adequate that will also promote optimal health.
Vegetarians who base their diets entirely on plant foods should take care in selecting foods to meet their nutritional needs. This is especially true for growing children, pregnant and lactating women, and the elderly. Vegetarian diets which include dairy foods and/or eggs provide all the nutrients needed, and have been shown to be healthful in a variety of populations. Since some dairy products are high in saturated fat, it is preferable to consume small amounts of these and to emphasize nonfat and low-fat products.
Plant foods are naturally devoid of vitamin B12, and individuals who avoid dairy products and/or eggs need a regular and reliable source of this vitamin, such as B12-fortified breakfast cereals, vegetable protein products and milk alternatives, or a vitamin preparation.
Although leafy and green vegetables are rich sources of calcium, consuming these foods in amounts adequate to meet the needs of some individuals may present a problem. Other calcium-rich plant food items which may be emphasized are tofu (made with calcium sulfate), calcium-fortified fruit juices and milk alternatives, some nuts, and dried fruits.
In the United States, the principal dietary source of vitamin D is milk, fortified with this vitamin. Diets which exclude milk, including those that are based entirely on plant foods, may require a supplementary source of vitamin D in the absence of adequate sunlight exposure. This is likely to occur in latitudes farther from the equator and during the winter months. Examples of vitamin D-fortified plant foods are some breakfast cereals and milk alternatives.
Many equate vegetarian diets with low-fat diets. Very low-fat vegetarian diets have proven helpful in therapeutic approaches to several disease conditions; thus, some individuals advocate low-fat vegetarian diets for everyone. Although it is easier to design a diet very low in both total and saturated fat in the context of a vegetarian diet, this should not imply that most vegetarians consume a low-fat diet. The average total fat intake of vegetarians varies widely (15 to 40 percent of daily energy) and the whole range of fat intake is compatible with excellent health.
Unrefined plant sources of fat, such as nuts, seeds, avocados, and olives are generously consumed by some vegetarians and not as much by others. These foods are sources of unsaturated fats, as well as antioxidants, phytochemicals, and dietary fiber. According to surveys, vegetarians consume more nuts more frequently than non-vegetarians. This is not a recent or local phenomenon. In India, with a millennium of vegetarian tradition, peanuts and peanut oils are a prominent part of the diet. Studies of vegetarians in the West during the first half of this century show that nuts provided 6 to 15 percent of the daily calories. Vegetarian Seventh-day Adventists in California eat nuts more frequently than their non-vegetarian counterparts, and much more than the general population.
The Adventist Health Study reports that men and women consuming nuts four or more times a week lowered their risk of heart disease by 50 percent and increased life expectancy by several years, as compared to those who hardly ever ate nuts. Experimental trials show that specific nuts lower blood lipids, and similar beneficial effects have been described for olive oil, avocados, and other unrefined plant-fat sources. Incorporating these foods in the diet may increase fat in the diet, but also contributes texture, aroma, and flavor.
Hydrogenated vegetable oils, such as are contained in margarines, shortening, and many commercial bakery products and snack foods, may have detrimental health effects and should be avoided. Tropical oils (coconut, palm kernel, and palm oils) are high in saturated fat and should be limited.
Currently, public health recommendations for total fat in the diet suggest keeping fat intake below 30 percent of the total energy (calories), based on data from Western populations where a major portion of dietary fat comes from eating animal foods and fat, as well as highly processed snack-type fatty foods. It is not clear if the same recommendations apply to vegetarians whose dietary fat comes mostly from unrefined plant food sources.
Fluid intake among vegetarians is higher than the general population. Some vegetarians drink as much as two to three liters of fluid a day, including water, freshly prepared fruit and vegetable juices, a variety of hot teas, and soups. Excluding water, these examples may represent an additional source of micronutrients and phytochemicals in the diet. A generous fluid intake is useful in treating several diseases and there is some research on the health-promoting effects and specific disease prevention of such a lifestyle characteristic.
Individuals choosing to follow a vegetarian diet often choose additional healthy lifestyle habits such as regular physical exercise, frequent exposure to sunlight, and fresh air. These are all factors considered essential to achieving and maintaining optimal nutrition and a healthy body weight.
Sufficient skin exposure to sunlight produces an adequate amount of vitamin D. In the absence of frequent sunlight exposure, vitamin D becomes an important nutritional factor and a dietary requirement. Nutrition sources include fortified foods such as cereals and dairy.
Daily exposure to fresh air and outdoor activities is also desirable and may have an added mental--as well as physical-- benefit. The Surgeon General recommends that all adults participate in regular, daily physical activity that is aerobic in nature and promotes fitness and well-being. Physical activity should be balanced with energy intake to ensure a healthy body weight.
Loma Linda University Authors
Joan Sabaté, MD, DrPH, associate professor and chair of nutrition, School of Public Health
Ella Haddad, DrPH, RD, associate professor of nutrition, School of Public Health
Crystal Whitten, MS, RD, assistant professor of nutrition and dietetics, School of Allied Health Professions
Larry Kidder, MA, editor, University relations office
The following persons have been instrumental in providing feedback and guidance in the preparation of this document.
John Anderson, University of North Carolina, Chapel Hill, North Carolina, USA
Diane Butler, Sanitarium Health Food Company, Sidney, Australia
Winston Craig, Andrews University, Berrien Springs, Michigan, USA
Suzanne Havala, The Vegetarian Resource Group, Baltimore, Maryland, USA
Tim Key, Imperial Cancer Research Fund, University of Oxford, Oxford, England, UK
Lawrence Kushi, University of Minnesota, Minneapolis, Minnesota, USA
Mark Messina, Nutrition Matters, Inc., Port Townsend, Washington, USA
David Nieman, Appalachian State University, North Carolina, USA
Helen Roe, Preventive Medicine Research Center, Sausalito, California, USA
Walter Willett, Harvard University, Boston, Massachusetts, USA