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Vegan Diet

Why Do People Follow This Diet?

Though people may choose a vegan diet for other reasons, they often fall into three broad categories: health, ethical, and spiritual.

  • Health-motivated vegans believe that avoiding animal foods will help them prevent and treat chronic conditions such as heart disease, diabetes, and cancer. They may also cite concerns about antibiotics, hormones, disease-causing organisms (like the cause of mad cow disease), heavy metals, and other pollutants that may be present in meat, dairy products, fish, and eggs.
  • Vegans motivated by ethics are concerned about the environmental and social impacts of raising livestock for food, since much more land is needed to support populations eating an animal-based diet than a plant-based diet, and since livestock production is a major contributor to greenhouse gases. They may also object to the inhumane treatment of animals in modern, industrialized farming.
  • Historically, both vegans and vegetarians have been motivated by spiritual and religious ideas. The first promoters of a fleshless diet believed that physical and spiritual purity were inherently linked, that a plant-based diet cleansed the body and could help them achieve a higher spiritual state. Some spiritually motivated vegans feel that veganism helps them to live in spiritual harmony with people around the world, animals, and the Earth. Veganism may also be part of religious doctrine.

What Do the Advocates Say?

Plenty of scientific evidence suggests that vegans and 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. These health differences persist even when lifestyle factors like smoking and physical activity are taken into account. A vegan diet in particular appears to be the most protective against breast and uterine cancers. In a five-year study of more than 73,000 participants, both vegans and vegetarians had a lower risk of death 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.

When comparing the nutrient composition of various diets, vegan diets rank as the healthiest—healthier than omnivorous, pesco-vegetarian, semi-vegetarian, and vegetarian. This appears to be due to the vegan diet being high in health-promoting foods/compounds and low in less healthful items:

  • Vegans may have a lower caloric intake than vegetarians and meat-eaters. Modest calorie restriction prevents overweight and obesity, type 2 diabetes, heart disease, and cancer, and is associated with increased longevity.
  • Vegan diets contain more fiber. Non-meat eaters consume two to three times as much fiber as do meat eaters, and among them, vegans consume the most. Fiber helps regulate blood sugar levels, protects the heart and blood vessels, and may protect against colon and other cancers.
  • Vegan diets may be high in antioxidants. Antioxidants are found mostly in plant foods and protect cells from free-radical damage. Dietary antioxidants may protect against heart disease, arthritis, cancer, neurological diseases, and other diseases that are generally related to aging.
  • Vegan diets may be high in isoflavones. Isoflavones are plant compounds, found mostly in soy foods, which may improve bone health and reduce prostate cancer and breast cancer risks.
  • Vegan diets may be high in 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.
  • Vegan diets may be high in phytochemicals. Phytochemicals are a broad group of special compounds found only in plants. They have a wide range of positive effects in the human body: some help clear toxins from the body, some stimulate the immune system, some regulate cell growth and prevent cancerous changes, and some reduce the harmful effects of excessive exposure to hormones and hormonally active chemicals.
  • Vegan diets may be high in healthy fats. Vegans get a lot of 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.
  • Vegan diets may be lower in unhealthy fats. Fats from meat, dairy foods, and eggs, contain high amounts of arachidonic acid (an omega-6 polyunsaturated fat) and long-chain saturated fats that have been linked to health problems.
  • Vegan diets contain less heme iron. Heme iron is 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, has been found to increase risks of heart disease, diabetes, and some cancers.
  • Vegan diets may contain less 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?

The most common criticism of a vegan diet is that it is low in certain nutrients:

  • Protein: While vegans do typically eat less protein than vegetarians and meat-eaters, they are not necessarily protein-deficient, as long as they consume legumes, whole grains, nuts, and seeds, which are excellent sources of protein. By including a variety of foods from each of these categories, and by properly combining them, vegans may get the protein they need, including all of the essential amino acids (protein building blocks that must be obtained from the diet).
  • Vitamin B12: This is a nutrient found mainly in animal foods. Some plant foods, such as seaweeds (especially nori) and mushrooms, are good sources of vitamin B12, and the bacteria involved in fermentation and culturing contribute B12 to foods such as tofu, miso, tempeh, natto, kimchi, and sauerkraut. Still, studies find that a majority of vegans do not get enough B12, so a supplement is probably a good idea.
  • Calcium: Vegans don't eat dairy foods but may get calcium from green vegetables, nuts and seeds, seaweeds, soy foods, and other legumes. Still, they get less calcium than vegetarians and omnivores and their intake is typically below the recommended level. Studies have found that vegans are no more likely to develop osteoporosis or experience bone fractures than vegetarians or omnivores, despite their lower calcium intake (indeed, excessive meat eating appears to be linked to higher rates of osteoporosis and fractures).
  • Vitamin D: Vegans get less dietary vitamin D than vegetarians and omnivores. Low vitamin D levels are usually a reflection of too little sun exposure, but since many people can’t or don’t get enough sun all year to keep their levels up, some foods (mainly dairy foods) are vitamin D fortified. Fish is the best natural source of vitamin D, while meat, eggs, and unfortified dairy foods have small amounts. Vegans can get some vitamin D from mushrooms,but are well-advised, like everyone else, to eat fortified foods (for vegans, this usually means soy- and grain-based milk substitutes) and to take a supplement.
  • Iron: Vegans get most of their iron from legumes and leafy green vegetables, while nuts, seeds, whole grains, and dried fruit can provide small amounts. The non-heme iron from plants is harder to absorb and use than heme iron, which comes exclusively from animals and fish, and as a result, vegans may need to get more iron than meat-eaters to keep their iron stores up. Nevertheless, vegans do not appear to be more prone to iron deficiency anemia than non-vegans, and may even be protected from the harmful effects of excess iron.
  • Zinc: Zinc deficiency is more common in vegans than meat eaters. Even vegetarians appear to have slightly better zinc status than vegans. While meat, fish, dairy, and eggs are the major sources of zinc for most people, vegans get zinc from legumes, nuts, seeds, and oatmeal. Vegans generally need more dietary zinc than non-vegans, 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) can improve the availability of zinc in legumes and seeds.
  • Iodine: Vegans eat less iodine than pesco-vegetarians and omnivores. Critics of vegan diets suggest that low iodine intake, along with high consumption of anti-thyroid chemicals from soybeans and cabbage, broccoli, kale and related vegetables, puts vegans at risk for thyroid disorders. A study comparing vegans, vegetarians, and omnivores found that vegans had the lowest iodine levels but there were no differences in thyroid function between people espousing these different diets. Vegans get iodine from seaweed, sea salt, and iodized salt.

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The information presented by Healthnotes 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 December 2019.