More and more people are choosingto be vegetarian. And for good reasons. At present, about 2.3 percent of the American adult population, or nearly 5 million people, consistently follow a vegetarian diet, while about 1.4 percent of the adult population are reported to be vegan. In addition, many nonvegetarian consumers report eating some meatless meals each week, including ordering vegetarian meals when they eat out. Fast-food restaurants are now offering a variety of meatless options. This increasing interest in vegetarianism is reflected in the proliferation of web sites, magazines, and cookbooks with vegetarian content.
Many people choose to go vegetarian for health reasons. Others choose a vegetarian diet because of their spiritual or religious principles, out of concern for the environment or the ethical treatment of animals. Still others cite economic reasons and world hunger issues as their motivation for following a meat-free diet.
The American Dietetic Association has taken the position that appropriately planned vegetarian diets are both healthful and nutritionally adequate. In some cases, fortified foods can be useful sources of key nutrients for vegetarians. The use of soy and other fortified beverages and juices, meat analogs, and breakfast cereals can significantly improve the nutritional status of a vegetarian, especially with respect to calcium, vitamin B12, vitamin D, omega-3 fatty acids, and zinc.
Vegetarian diets and childhood
Well-planned lacto-ovo-vegetarian and vegan diets can be appropriate for a successful pregnancy and lactation, and they satisfy the nutrient needs of infants, children, and adolescents and promote normal growth in children.1 Birth weight and length of babies born to vegetarian mothers are no different from those born to nonvegetarian mothers. Vegetarian diets in childhood and adolescence can encourage the establishment of lifelong healthful eating patterns and can offer health advantages. Vegetarian children and adolescents have higher intakes of health-promoting fruits, vegetables, and fiber than nonvegetarians. Vegetarian children are reported to be leaner and to have lower serum lipid levels and lower blood pressure levels.1 2
The growth of lacto-ovo-vegetarian children is quite similar to that of their nonvegetarian peers.1 3 Some studies suggest that vegan children tend to be slightly smaller but within the normal ranges of the standards for height and weight.1 Poor growth in children has primarily been seen in those on very restricted diets, such as macrobiotic or low calorie, high bulky ones that do not provide enough calories for growing children.4
Risk of chronic diseases
Well-balanced vegetarian diets also provide health benefits in the prevention and treatment of chronic diseases. Vegetarians demonstrate lower rates of death from heart disease, lower LDL cholesterol levels, lower blood pressure levels, lower rates of hypertension, and lower incidence of type 2 diabetes, prostate cancer, and colon cancer than nonvegetarians.
Among Adventists, vegetarian eating patterns are associated with a lower body weight.5 In the Oxford study, body mass index values were higher in nonvegetarians compared with vegetarians in all age groups for both men and women.6 In a cross-sectional study of almost 38,000 adults, meat-eaters had the highest age-adjusted mean BMI and vegans the lowest, while other vegetarians had intermediate values.7 In theEPIC-Oxford Study, weight gain over a five year period was lowest among those who changed to a diet containing fewer animal foods.8
Early results from the Adventist Health Study-2 suggest that vegans have a lower body mass index than other vegetarians. This would be expected to provide a lower risk of heart disease, hypertension, cancer, and diabetes for vegans.
The lower risk of death from heart disease seen in vegetarians can be explained partly by differences in blood lipid levels. A reduction in total and LDL-cholesterol levels is usually seen when subjects switch from their usual diet to a vegetarian one. In one study, the incidence of heart disease was estimated, based on blood lipid levels, to be 24 percent lower in lifelong vegetarians and 57 percent lower in lifelong vegans when compared to meat eaters.9
Non-flesh diets reduce the risk of cardiovascular disease through other means than lowering blood lipid levels as well. For example, soy protein, fruits, vegetables, whole-grains, and nuts are all reported to lower the risk of mortality from cardiovascular disease. Flavonoids and other phytochemicals appear to have protective effects as antioxidants, in reducing blood clotting, as anti-inflammatory agents, and in improving the function of blood vessel walls.10 A near-vegan diet high in phytosterols, soluble fiber, nuts, and soy protein has been shown to be as effective as a low-saturated fat diet plus a statin for lowering serumLDL-cholesterol levels!11
Furthermore, lower rates of hypertension are also typically seen among vegetarians compared to nonvegetarians,5 9 possibly due to the lower mean body weight of vegetarians. Additional factors in vegetarian diets that could result in lower blood pressure levels include the higher levels of potassium, magnesium, antioxidants, unsaturated fat, and fiber. Many studies report that consumption of 5 to 10 servings of fruit and vegetables per day significantly lowers blood pressure.12 Preliminary results from the Adventist Health Study-2 suggests that vegans have an even lower rate of hypertension than do other vegetarians.9
Diets that are predominantly plant-based also appear to reduce the risk of type 2 diabetes.13 In the Adventist Health Study, the age-adjusted risk for developing diabetes was two-fold greater in nonvegetarians, compared with their vegetarian counterparts.5 Because a lower BMIand a higher fiber intake improve insulin sensitivity, these factors may partly explain the protective effect of a vegetarian diet. A higher intake of vegetables, whole grain foods, legumes, and nuts have all been associated with a substantially lower risk of insulin resistance and type 2 diabetes, as well as improved glycemic control in either normal or insulin-resistant individuals.14
People consuming about 3 servings per day of whole grain foods are 20 to 30 percent less likely to develop type 2 diabetes than low consumers (less than 3 servings per week).15 In the Nurses’ Health Study, the risk of diabetes for those consuming nuts 5 or more times a week was 27 percent lower than those who almost never ate nuts.16 In another large study, a high intake of peanuts, soybeans, or other legumes, was protective against type 2 diabetes mellitus. The risk of type 2 diabetes was 38 percent and 47 percent lower, for those consuming a high intake of total legumes and soybeans, respectively, compared to a low intake.17 One study examining vegetable intakes found that the risk of type 2 diabetes was 28 percent lower for women consuming the most vegetables, compared to those who consumed the least amount. All of the individual vegetable groups were inversely associated with the risk of type 2 diabetes.18
Fiber-rich vegan diets are characterized by a low to moderate glycemic load.19 In a five month randomized clinical trial, a low-fat vegan diet was shown to considerably improve glycemic control in persons with type 2 diabetes, resulting in 43 percent of the subjects reducing diabetes medication.20 These results were superior to those obtained from following standard American Diabetes Association guidelines.
Vegetarians tend to have an overall cancer rate lower than that of the general population. Data from the Adventist Health Study revealed that non-vegetarians demonstrated a substantially increased risk for both colorectal and prostate cancer compared with vegetarians, but there were no significant differences in risk of other cancers between the groups.5 Since obesity is a significant factor for increased risk of cancer,21 the lower BMI of vegetarians may be a significant factor.
Studies have consistently shown that regular consumption of fruit and vegetables is strongly associated with a reduced risk of cancer.22 Fruits and vegetables contain a complex mixture of phytochemicals, which may act synergistically to provide the cancer-protective effects. Flavonoids and other phytochemicals interfere with several cellular processes involved in the progression of cancer. These mechanisms include the inhibition of cell proliferation, inhibition of DNA adduct formation, inhibition of signal transduction pathways, induction of cell cycle arrest and apoptosis, induction of phase 2 enzymes, and the inhibition of angiogenesis.23
According to the recent World Cancer Research Fund report, fruit and vegetables are protective against cancer of the lung, mouth, esophagus, and stomach, and to a lesser degree other sites.21 The regular use of legumes also provides protection against stomach and prostate cancer. Fiber, vitamin C, carotenoids, flavonoids, and other phytochemicals in the diet exhibit protection against various cancers. The allium vegetables, such as onions, leeks, and garlic protect against stomach cancer, and garlic protects against colorectal cancer as well. Tomatoes, and other foods, rich in the carotenoid, lycopene, are reported to protect against prostate cancer.21
Soy foods used by vegetarians also possess valuable anti-cancer properties. Many studies conducted in high-soy-consuming Asians show a significant trend of decreasing risk of breast cancer with increasing soy food intake. On the other hand, meat consumption has been linked in some studies, but not all, with an increased risk of breast cancer. In one study, breast cancer risk increased by 50 to 60 percent for each additional 3 ounces per day of meat consumed!24
A high dairy intake, however, may weaken the protective effect of a vegetarian diet. For example, use of dairy and other calcium-rich foods has been associated with an increased risk of prostate cancer.21 25 In addition, consumption of red meat and processed meat are consistently associated with an increase in the risk of colorectal cancer.21 On the other hand, the intake of legumes was negatively associated with risk of colon cancer even in non-vegetarians.5
Studies published over the past two decades suggest no differences in bone mineral density between omnivores and lacto-ovo-vegetarians.26Although very little data exist on the bone health of vegans, some studies suggest that bone density is lower among some vegans compared with omnivores.27 28 The female Buddhists in these studies had especially low intakes of protein and calcium—which is associated with bone loss and fractures at the hip and spine in the elderly.29 30
A recent British study comparing the risk of bone fracture in omnivores to that of vegans found a 30 percent higher risk in the vegans due to their lower calcium intake.31 However, the fracture rates of those vegans who consumed higher calcium levels (over 525 mg calcium per day) were not different from the fracture rates of omnivores. Dairy products, dark green leafy vegetables, and calcium-fortified plant foods, including fortified ready-to-eat cereals, soy and rice beverages, and juices, can provide readily available calcium for the vegetarian.
A high intake of animal protein may produce an increased excretion of calcium in the urine.32 Postmenopausal women with diets high in animal protein and low in plant protein revealed a high rate of bone loss and a greatly increased risk of hip fracture.33
The maintenance of acid-base balance is critical for bone health. An acid-forming diet is known to increase urinary calcium excretion compared with a base-forming diet.34 An increased fruit and vegetable consumption has a positive effect on the calcium economy and markers of bone metabolism.35 The high potassium and magnesium content of fruits, berries and vegetables, with their alkaline ash, makes these foods useful dietary agents for inhibiting bone resorption.36 Bone mineral density of the hip and spine of premenopausal women was found to be 15 to 20 percent higher for women with the highest potassium intake compared with the lowest.37 Results from two large population studies suggest that a high intake of vitamin K from green, leafy vegetable is also associated with a low risk of hip fracture.38 39 In addition, studies suggest that isoflavone-rich soy protein decreases spinal bone loss in postmenopausal women.40 The isoflavones both significantly inhibit bone resorption and stimulate bone formation.41
Other protective effects
Soy-based vegan diets appear to slow the progression of kidney disease.42 Vegetarians appear to be at lower risk of developing dementia than nonvegetarians.43 This reduced risk may be due to the lower blood pressure seen in vegetarians or to their higher antioxidant intake.
The final word
Well-planned vegetarian diets are nutritionally adequate for infants and for growing children. Following a vegetarian diet can effectively lower your risk of heart disease, high blood pressure, diabetes, cancer, and other health conditions.