Healthy and Smart Vegetarian Eating
By Donald R. Davis, Ph.D.
Throughout human history, some persons have chosen vegetarian diets for philosophical, health, and economic reasons. In a 2000 survey, 2.5% of adults in the United States reported consistently consuming a vegetarian diet, defined as one without meat, fish, or fowl. About 1 % of adults are vegans-total vegetarians who also avoid eggs, milk, and milk products. Often vegetarianism has been supported by various religious groups and accompanied by avoidance of refined foods, alcohol, tobacco, and illegal drugs. Well chosen vegetarian diets can be nutritionally adequate and healthful. They also offer one way to help prevent or treat common diseases. Here we will highlight some health benefits found in vegetarians and emphasize certain nutrients that need special attention by vegetarians, especially vegans.
Well chosen vegetarian diets can be nutritionally adequate and healthful.
Hundreds of studies show that diets rich in vegetables, fruits, and whole grains help prevent or treat most of our major chronic disorders. Thus, professional associations such as the American Cancer Society recommend primarily plant-based diets with limited amounts of animal foods. Vegetarians compared to others have less obesity, heart disease, cancer, diabetes, hypertension, constipation, diverticular disease, gallstones, and possibly age-related dementia. Vegetarians usually consume more vegetables, antioxidant vitamins, phytochemicals, fiber, whole grains, and soy protein. They generally consume less saturated fat, but not necessarily less total fat, and less alcohol, sugar, and vitamin B12. Because of the many dietary and lifestyle differences between vegetarians and others, including activity levels and tobacco use, it is hard to know which aspects of vegetarian lifestyles are most beneficial.
Some nutrients are difficult or impossible to obtain from plant sources, so vegetarians, especially vegans, should give special attention to these nutrients, primarily vitamin B12, iron, calcium, riboflavin, omega-3 fats, vitamin D, and protein.
Vitamin B 12 is not reliably present and active in any plant food. A few seaweeds and algae contain it, but they also contain vitamin B12 “analogs” that interfere with its function, making it inactive. Vegetarians who regularly consume eggs, milk, and milk products can obtain sufficient vitamin B12 from these foods, but other vegetarians should use fortified foods or a supplement. Commonly fortified foods include breakfast cereals, meat substitutes, nutritional yeasts, and soymilks (check their food labels). The current Recommended Dietary Allowance (RDA) is 2.4 micrograms, and the “Daily Value” used on food labels is 6 micrograms (the 1968 RDA).
The form of iron in plants is poorly absorbed and subject to inhibition by teas, coffee, cocoa, and calcium. However, vitamin C and other substances in fruits help increase the absorption of plant source iron. The recommended intake for vegetarians is 1.8 times the intake for non-vegetarians, which for adult vegetarians translates to 14 mg per day for men and 32 mg per day for menstruating women. Good sources include tofu and other soy foods, beans, nuts, seeds, meat substitutes, some sea vegetables, fortified cereals, and wheat germ.
Calcium stands out in milk and fortified soymilk but is less abundant in plants. The best plant sources are green leafy vegetables, broccoli, almonds, almond butter, sesame seeds, sesame butter, tahini, fortified cereals and juices, com tortillas made with lime (calcium carbonate), tofu made with calcium sulfate, and soybeans. Canned fish with bones, such as sardines or salmon, are also good sources. The RDA is 1000 to 1200 mg per day for adults.
Riboflavin is prominent in milk, eggs, almonds, nutritional yeasts, fortified cereals, enriched grain products, mushrooms, sea vegetables, fortified soymilks, and wheat germ. The RDA is 1.3 mg for men and 1.1 mg for women. Omega-3 fatty acids are rich in fatty fish. Milk and ordinary commercial eggs are modest sources, but eggs with enhanced (more natural) omega-3 levels are now widely available. Plant sources include soybeans, tofu, walnuts, flax seeds (best used as a meal), and chia seeds. Pinon or pinyon nuts from the American southwest are a good source but not the more commonly available pignoli or pine nuts from the Mediterranean area. Canola oil, soy oil, and flax oil are less recommendable sources because, like all oils, they lack the broad range of nutrients found in whole foods.
Vitamin D can be obtained from adequate sunlight exposure, roughly 10 minutes per day on the face, hands, and forearms of light-skinned persons for much of each year (at the middle latitudes of the U.S.). Those with little sun exposure need dietary sources or a supplement. Fish and shellfish are the richest of the few natural sources. Milk is fortified with vitamin D, and egg yolks and mushrooms have modest amounts. For vegans the most common dietary sources are fortified cereals and soymilk, or supplements. The natural form of vitamin D is labeled vitamin D 3 or cholecalciferol, but D2 or ergocalciferol is also used sometimes. The commonly recommended adult intake is 200 to 600 IV (5 to 15 micrograms) per day, though some authorities now recommend 800 IV (20 micrograms) per day.
Protein is rich in most animal foods, and it used to be thought by many that vegetarians would be deficient. Now there is little concern, except for vegan toddlers and children who have high protein needs and for vegetarians consuming substantial non-whole foods such as sugar, honey, added fats, white flour, and rice. Also at risk are sedentary or elderly vegetarians with low calorie needs and vegetarians on low-calorie diets. Elsewhere in this issue, Rebecca Kirby discusses vegetable sources of protein.
A few cautions seem in order, especially for some teens and others who try vegetarianism in a casual or uninformed way. Our poorest, non-whole foods can qualify as vegan, namely added sugars, added fats, and refined grains. These are the major ingredients in all “junk” foods. The mere avoidance of animal foods is no recipe for good nutrition. Further, the two staples of most vegetarians, grains and legumes, were never widely consumed until our development of agriculture, a recent event in biological time. Because of biochemical individuality, it seems unwise to assume that everyone is well adapted to vegetarianism, especially veganism.
Vegetarian diets can promote superior health, and they may be recommended for good reasons. But, just like non-vegetarian diets, they can be done either well or poorly. The difference lies in knowledge and good choices within the beliefs, preferences, and needs of each individual.