A vegetarian is a person who does not eat meat, including fowl or seafood, or products containing these foods. A wide spectrum of dietary practices is considered vegetarian. A vegetarian whose diet consists of foods of plant origin only is a total vegetarian or vegan. However, many vegetarians also consume eggs (ovovegetarian), dairy products (lactovegetarian), or both eggs and dairy products (lacto-ovovegetarian).
The two most common definitions for vegetarian diets in the research are vegan diets, which are devoid of all flesh foods, and vegetarian diets, which are devoid of all flesh foods but do include eggs, dairy products, or both. According to the Academy of Nutrition and Dietetics Evidence Analysis Library, these broad categories mask important variations within vegetarian diets. Thus, the absolute categorization of vegetarian dietary practices is difficult and may result in unclear relationships between vegetarian diets and other health factors
Vegetarian diets are adopted for a variety of health, ecological, economical, philosophical, and ethical reasons. Vegetarian diets offer a number of health advantages, including lower blood cholesterol levels, lower blood pressure levels, and lower risks of hypertension, heart disease, and type 2 diabetes. Vegetarians tend to have a lower body mass index and lower overall cancer rates. Vegetarian diets tend to be lower in saturated fat and cholesterol and have higher levels of dietary fiber, magnesium, potassium, folate, antioxidants (eg, vitamins C and E), carotenoids, flavonoids, and other phytochemicals. These nutritional differences may explain some of the health advantages of a varied, balanced vegetarian diet.
Planning the Diet
A vegetarian diet can be made nutritionally adequate by careful planning and giving consideration to the following guidelines.
· Choose a variety of foods, including fruits, vegetables, whole grains, legumes, nuts, seeds, tofu or other soy products, and, if desired, dairy products and eggs.
· Choose whole or unrefined grain products whenever possible, instead of refined products.
· Minimize intake of foods that are highly sweetened, high in sodium, or high in fat, especially saturated fat and trans fatty acids.
· If animal foods such as dairy products and eggs are used, choose lower-fat dairy products and use both eggs and dairy products in moderation.
· Use a regular source of vitamin B12, and, if sunlight exposure is limited, provide a source of vitamin D. In addition to these guidelines, the DRIs are a valuable resource for meal planning
The body’s need for essential amino acids can be met by consumption of animal or plant sources of protein. Although plant foods contain less of the essential amino acids than do equivalent quantities of animal foods, a plant-based diet can provide adequate amounts of amino acids when energy needs are met and a varied diet is consumed on a daily basis. A mixture of different proteins from unrefined grains, legumes, seeds, nuts, and vegetables will complement each other in their amino acid profiles to meet nutritional needs. Estimates of protein requirements may vary based on dietary choices selected, particularly for vegans. Isolated soy protein can meet protein needs as effectively as animal protein, whereas wheat protein eaten alone may be 50% less usable than animal protein.
Unfortified plant foods do not contain significant amounts of active vitamin B12. Although the requirement for vitamin B12 is relatively small, vegetarians must include a reliable source of vitamin B12 in their diets to reduce their risk of developing a deficiency.
Lacto-ovovegetarians can obtain adequate vitamin B12 from the regular consumption of dairy foods, eggs, fortified foods, or supplements. Folacin-rich vegetarian diets may mask the hematological symptoms of vitamin B12 deficiency; therefore, a deficiency may go undetected until the manifestation of neurological signs and symptoms
Calcium is present in many plant foods and fortified foods. The calcium intake of lactovegetarians is comparable to or higher than that of non-vegetarians. However, the calcium intake of vegans is generally lower than that of lactovegetarians and non-vegetarians and is often below the recommended level.
In one study, the risk of bone fracture was similar for lacto-ovovegetarians and meat eaters, whereas vegans had a 30% higher risk of fracture possibly due to their considerably lower mean calcium intake. A diet that provides foods with relatively high ratios of sulfur-containing amino acid proteins, such as eggs, meat, fish, poultry, dairy products, nuts, and many grains, may increase calcium loss from the bones.
Excessive sodium intake may also promote calcium loss from the bones. Lower oxalate greens, such as bok choy, broccoli, Chinese cabbage, collards, and kale, and fruit juices fortified with calcium citrate malate are good sources of highly bioavailable calcium (50% to 60% and 40% to 50%, respectively), while calcium-set tofu, and cow’s milk have good bioavailability of calcium (30% to 35%), and sesame seeds, almonds, and dried beans have a lower bioavailability (23% to 27%)
Vitamin D status depends on sunlight exposure and intake of vitamin D–fortified foods or supplements. If sun exposure and intake of fortified foods are insufficient to meet nutritional needs, vitamin D supplements are recommended.
Because vegan diets tend to be high in bulk, it can be challenging for vegans, especially infants, children, and adolescents, to meet their energy needs. Frequent meals and snacks and the use of some refined foods (such as fortified breakfast cereals, breads, and pasta) and foods higher in unsaturated fats can help vegan children meet their energy and nutrient needs
The non-heme iron found in plant foods is more sensitive than heme iron to both inhibitors and enhancers of iron absorption. The inhibitors of iron absorption include phytate, calcium, and polyphenols in teas (including some herb teas), coffee, and cocoa. Some food preparation techniques, such as soaking and sprouting beans, grains, and seeds and the leavening of bread, can diminish phytate levels and thereby enhance iron absorption.
In addition, vitamin C and other organic acids in fruits and vegetables consumed by vegetarians can substantially enhance iron absorption and reduce the inhibitory effects of phytates, leading to improved iron status.