What is a vegetarian diet?

Overview

A vegetarian diet has many health benefits and may actually reduce the incidence of some diseases. The American Dietetic Association (ADA) states that properly managed vegetarian diets “are healthful, nutritionally adequate, and provide health benefits in the prevention and treatment of certain diseases.”

The defining characteristic of a vegetarian diet is abstention from meat consumption. There are, however, a number of different types of vegetarian diets, ranging from the lacto-ovo vegetarian diet, which includes dairy products and eggs, to the vegan diet, which excludes all meats and animal products. The focus here is the lacto-ovo vegetarian diet.

Mechanism of Action

A vegetarian diet works through eliminating the consumption of meat products that are high in saturated fat and cholesterol, while increasing the intake of high-fiber, cholesterol-free, plant-based foods.

Uses and Applications

The transition to a healthy vegetarian diet can be simple with some education and planning. A healthy vegetarian diet centers on decreasing fat intake and increasing fiber intake. This can be accomplished through emphasizing fresh fruits and vegetables, beans and other legumes, and whole-grain foods that are high in fiber and low in cholesterol and saturated fat. The diet avoids processed foods and refined sugar. A healthy vegetarian diet fulfills all these criteria.

Many nutritionists, however, recommend that a person transition to a vegetarian diet in stages, allowing the body to adjust by substituting a few meat meals each week with vegetarian food. One should start by reducing and eliminating red meat, then gradually eliminating pork, poultry, and fish. A simple way to make the transition is to use readily available soy-based meat substitutes such as tofu, tempeh, and textured vegetable protein, which are high in protein and can have a meat-like texture and taste.

In 2003, the ADA published a set of guidelines for North American vegetarian diets, recommending the following elements:

Whole grains. Six servings per day, including wheat, oatmeal, quinoa, couscous, and rice. Grains provide fiber, iron, and B vitamins. If possible, one should soak grains overnight to increase their digestibility.

Vegetables and fruits. Six servings per day, including carrots, leafy greens, collards, brassicas (broccoli, cabbage, brussels sprouts), apples, oranges, and bananas. Brassicas are rich in vitamin C, fiber, and carotenoids. Leafy greens and collards are sources of calcium, protein, and many vitamins, including C and A. Fruits are rich in vitamins B and C and calcium. Fresh vegetables and fruits have the highest vitamin content. One should steam or lightly cook vegetables to maintain higher nutrient value.

Legumes, nuts, and other protein-rich foods. Five servings per day, including beans, peas, soy, nuts, dairy foods, and eggs.

Fats. Two servings per day, including vegetable oils, walnuts, mayonnaise, butter, and margarine.

Calcium-rich foods. Eight servings per day, including milk, cheese, fortified soy and fruit juices, and leafy greens.

Scientific Evidence

Research has shown that people who eat a healthy vegetarian diet weigh less and have lower cholesterol levels, lower blood pressure, and lower rates of many diseases. Research also has shown that this diet can reverse the effects of atherosclerosis. The risk of men contracting prostate cancer and women getting breast cancer are almost four times as high for meat eaters, compared with those on a largely vegetarian diet. In addition, a vegetarian diet has been used successfully to treat osteoporosis, arthritis, allergies, asthma, gout, hemorrhoids, kidney stones, premenstrual syndrome, anxiety, and depression. A 2000 study of members of the Seventh-day Adventist Church (who practice a lacto-ovo vegetarian diet) indicated that these members live, on average, two years longer than persons on a meat-based diet.

In 2014, a study published in the Journal of the American Medical Association: Internal Medicine confirmed the connection between vegetarianism and lower blood pressure through a new meta-analysis of all previous studies conducted on the subject. The researchers reported that their analysis suggested that a vegetarian diet is about half as strong as taking medication in terms of keeping blood pressure down. Neal Barnard, one of the lead researchers of the study, also stated that he believes those who consume meat and subsequently animal fat have higher blood viscosity that leads to higher blood pressure.

Safety Issues

A well-planned vegetarian diet is a healthy and safe diet; however, vegetarians need to be aware of particular nutrients that may be lacking in diets without meat. These nutrients include protein, vitamin B12, vitamin A, vitamin D, calcium, iron, zinc, and N-3 fatty acids. It is possible to get these nutrients from plant-based foods, but they are not as abundant as in animal-based foods. To reap the benefits of a vegetarian diet, it is important to eat a diverse mix of whole grains, fresh vegetables, fruits, leafy greens, legumes, and nuts and to consciously reduce cholesterol and saturated fat intake by limiting dairy, eggs, and high-fat foods.

Animal-based proteins are complete proteins but are high in cholesterol. Research has shown that plant sources can meet the body’s need for protein as long as a variety of plant foods are consumed. Most plant proteins are incomplete, lacking one or more of the essential amino acids. However, vegetarians can easily overcome this lack by combining a variety of complementary plant sources. In general, combining legumes such as beans, soy, and peas with grains such as rice, wheat, and couscous (for example, in beans and rice, hummus and crackers, or peanut butter and bread) forms a complete protein.

Those vegetarians who regularly eat eggs and dairy foods get adequate amounts of vitamin B12
, yet the ADA recommends regular B12 supplements or foods fortified with B12. Vitamin A requirements can be met through eating carrots, leafy greens, or fruits (such as apricots, mangos, and pumpkins) that are rich in beta-carotene or by taking supplements. Vegetarians can get adequate amounts of vitamin D through regular exposure to the sun, by eating fortified foods, and by taking supplements.

Calcium is readily obtained by eating enriched soy products, nuts, legumes, dairy, and dark green vegetables such as broccoli and kale. Iron is available in raisins, legumes, tofu, potatoes, and leafy greens. Iron is absorbed more efficiently in the body if iron-rich foods are combined with those containing vitamin C, such as oranges, apples, and tomatoes. Zinc is abundant in pumpkin seeds, legumes, peas, lentils, whole grains, and soy products.

Vegetarians need to get adequate amounts of N-3 or omega-3 fatty acids. Vegetarian diets tend to be high in N-6 fatty acids but low in N-3 fatty acids (found in abundance in seafood and in some plants and nut oils). The body needs a balance of both. Vegetarian sources of N-3 fats include soy, walnuts, pumpkin seeds, and hemp seeds. Flaxseed oil is particularly rich in these fats.

Bibliography

Freston, Kathy. "Why Do Vegetarians Live Longer?" Huffington Post. TheHuffingtonPost.com, 26 Dec. 2012. Web. 28 Jan. 2016.

Hagler, Louise, and Dorothy R. Bates, eds. The New Farm Vegetarian Cookbook. 2nd ed. Summertown: Book, 1989. Print.

Hamblin, James. "Vegetarians and Their Superior Blood." Atlantic. Atlantic Media Group, 24 Feb. 2014. Web. 28 Jan. 2016.

“A New Food Guide for North American Vegetarians.” Available at http://www.metabolicdiet.com/pdfs/veg_food_guide.pdf. Outlines the basics of a balanced and healthy vegetarian diet.

Whoriskey, Peter. "Is a Vegetarian Diet Really Better for the Environment? Science Takes Aim at the Conventional Wisdom." Washington Post. Washington Post, 18 Dec. 2015. Web. 28 Jan. 2016.