Why Do People Follow This Diet?
People choose vegetarian diets for a variety of reasons, with health, environmental, social justice, and animal welfare concerns topping the list. Health-motivated vegetarians avoid meat to improve their health and to decrease their risk of chronic diseases, such as heart disease, diabetes, and cancer. They may also be concerned about the presence of antibiotics, hormones, disease-causing agents (like the cause of mad cow disease), and pollutants that may be concentrated in meats.
Others go vegetarian due to concerns about the environment (for example, livestock farming can cause deforestation, soil erosion, water pollution, and greenhouse gases). Others cite social justice issues, saying that animal-based diets require farming practices that contribute to poverty and world hunger by using too much land per person and by triggering the conversion of prime agricultural land around the world into grazing land.
Some vegetarians object to inhumane practices of modern-day animal farming. Others follow a vegetarian diet according to their religious custom. Finally, some people choose vegetarianism in an attempt to live more simply and economically, and in closer harmony with the way most of the world’s population eats.
What Do the Advocates Say?
It is well documented that vegetarians are healthier than people who eat meat: they are less likely to be obese, have lower rates of diabetes, high blood pressure, heart disease, and cancer (especially colon cancer), and live longer. Although many vegetarians also exercise and avoid smoking, evidence indicates that their good health is largely due to diet.
In a 5-year study of more than 73,000 participants, both vegans and vegetarians had a lower risk of dying for any reason (all-cause mortality) than omnivores. Even occasional meat eating was linked to higher mortality rates than vegetarian and vegan eating. Although differences between various meatless diets were small, it appeared that vegans were slightly more protected than vegetarians when compared to meat eaters. Only pesco-vegetarians (vegetarians who eat seafood) fared slightly better than vegans in the study.
Why are vegetarians healthier than non-vegetarians? This appears to be due to the vegetarian diet being high in health-promoting foods and low in less healthful items:
- Fiber: Vegetarians consume two to three times as much fiber as do meat eaters. Fiber helps regulate blood sugar levels, protects the heart and blood vessels, and may protect against colon and other cancers.
- Antioxidants: Antioxidants are found in a wide variety of plant foods. Antioxidants protect cells from oxygen-induced damage and may protect against heart disease, arthritis, cancer, neurological diseases, and other diseases that are generally related to aging.
- Phytochemicals: These special compounds found in plants have a wide range of protective effects in the human body. They help to detoxify carcinogens, stimulate the immune system, regulate cell growth, prevent cancerous changes, and reduce some of the harmful effects of excessive exposure to hormones.
- Isoflavones: These compounds, found mostly in soy foods, may improve bone health, and reduce prostate cancer and breast cancer risks.
- Lignans: Lignans are plant compounds found in the fibers of foods like nuts, seeds, and legumes. A high-lignan diet has been linked to lower levels of blood markers of inflammation and a lower risk of metabolic syndrome, a condition marked by obesity, diabetes, and insulin resistance. Lignans may also protect against breast cancer and perimenopausal depression.
- Healthy Fats: Vegetarians consume lots of healthy fats, including monounsaturated fats like those in almonds, olives, avocados, and macadamias, certain polyunsaturated fats like those in sesame, sunflower, and pumpkin seeds, as well as liquid oils, and medium-chain saturated fats like those in coconut and palm oils. These types of fats have been shown to improve carbohydrate and fat metabolism, reduce levels of inflammatory chemicals, and prevent diabetes and heart disease. Fats from meat, dairy foods, and eggs, on the other hand, contain high amounts of arachidonic acid (an omega-6 polyunsaturated fat) and long-chain saturated fats that have been linked to health problems. Even though lacto-ovo vegetarians eat some of these foods, they still consume less of these fats than omnivores.
- Less Heme Iron: Except for pesco-vegetarians, vegetarians do not consume the type of iron found in meat, fish, and poultry. Heme iron is necessary for healthy human functioning, and the body produces some from plant-derived iron and proteins. Excess heme iron, however, might increase the risk of heart disease, diabetes, and some cancers.
- Less Exposure to Carcinogens: Vegans are not exposed to the carcinogens that are found in red meat and processed meat products like cold cuts and hot dogs.
What Do the Critics Say?
Protein: Critics of vegetarianism commonly believe that vegetarians are protein deficient. However, vegetarians who consume legumes, whole grains, nuts, and seeds get enough protein. By including a variety of foods from each of these categories, and by properly combining these foods, vegetarians can get all of the essential amino acids (protein building blocks that must be obtained from the diet). In addition, vegetarians who supplement their plant-based diet with dairy, eggs, or fish add complete protein (providing all of the essential amino acids) through these foods.
Vitamin B12: Vitamin B12 is a nutrient found mainly in animal foods, including dairy, eggs, and fish, which are part of some vegetarian diets. Certain plant foods, like seaweeds (especially nori) and mushrooms, are also good sources. The bacteria involved in fermentation and culturing contribute B12 to foods like tofu, miso, tempeh, natto, kimchi, and sauerkraut. Despite all of these B12 sources, studies find that many vegetarians are B12 deficient, so a supplement is generally a good idea.
Calcium and Vitamin D: Some critics fault vegetarian diets for not providing sufficient calcium and vitamin D; however, researchers have found that vegetarians are no more likely to be deficient in these important nutrients than omnivores. This may be because most people who consider themselves vegetarian still consume dairy products. Vegans, who do not consume dairy foods, don’t get as much dietary calcium and vitamin D as vegetarians or omnivores.
Iron: Vegetarians get most of their iron from legumes and leafy green vegetables, with nuts, seeds, whole grains, and dried fruit contributing smaller amounts. Even though the non-heme iron found in plants is harder to absorb than heme iron from meat, poultry, and fish, vegetarians appear to have no higher risk of iron deficiency anemia than non-vegetarians, and may even be protected from the harmful effects of excess iron.
Zinc: While omnivores get zinc from meat and poultry, vegetarians rely on plant sources like nuts, seeds, legumes, and oatmeal, and any dairy, eggs, or fish they choose to include. Vegetarians typically need more dietary zinc than non-vegetarians, since the legumes and grains they rely on are high in phytates, compounds that can bind to zinc and prevent its absorption. Soaking, sprouting, and leavening (as with yeast) are strategies that can improve the availability of zinc in legumes and seeds.
Iodine: Critics of vegetarians who don’t eat fish say that by not getting enough iodine, and by consuming large amounts of anti-thyroid chemicals from soybeans and cabbage, broccoli, kale and related vegetables, they put themselves at risk for thyroid disorders. A study comparing vegans, vegetarians, and omnivores found that vegetarians were no more likely to be iodine deficient or have thyroid problems than non-vegetarians. Vegetarians who don’t eat fish still get iodine from seaweed, sea salt, and iodized salt.
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The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires June 2015.