Orit Ofir, Clinical dietitian (B Sc.)
Scientific research on vegetarian and vegan diets has undergone a revolution in the past two decades: from isolated studies that focused primarily on whether a plant based diet can cause nutritional deficiencies, to dozens of studies annually that investigate the efficiency of plant-based nutrition in the prevention and treatment of common diseases.
In 2009, The Academy of Nutrition and Dietetics (formerly the American Dietetic Association) published a position paper based on analysis of the scientific research on nutrition accumulated so far, :
“It is the position of the American Dietetic Association that appropriately planned vegetarian diets, including total vegetarian or vegan diets, are healthful, nutritionally adequate, and may provide health benefits in the prevention and treatment of certain diseases. Well-planned vegetarian diets are appropriate for individuals during all stages of the lifecycle, including pregnancy, lactation, infancy, child- hood, and adolescence, and for athletes.”
According to the report, vegetarians and vegans are at lower risk for cardiovascular diseases, Type II diabetes, cancer (mainly colon and prostate cancer), high blood pressure, diverticulitis (a disease of the large intestine), gallstones and probably dementia too.
It's important to note, that in all studies on which the report was based, biasing factors such as smoking habits, obesity etc. were neutralized.
Cardiovascular Diseases
Vegetarians are at a lower risk for cardiovascular illness compared to omnivores, with the risk for vegans even lower. One of the major studies showed that the risk for cardiovascular diseases among vegetarians was 24% lower in comparison to omnivores, and among vegans 57% lower.
Studies have shown that vegetarians and vegans have lower levers of LDL (the “bad cholesterol”).
A study from 2005 published in the prestigious journal “American Journal of Clinical Nutrition” found that nearly total vegan diet is as effective in lowering LDL levels as statin drugs combined with a diet low in saturated fat.
Obesity
Vegetarians tend to be slimmer than meat eaters, and vegans tend to be slimmer than vegetarians (but still within the healthy weight range).
Diabetes
Vegans and vegetarians have a lower risk of developing diabetes. Some studies showed that vegans and vegetarians are two times less likely to develop diabetes.
There is a link between consumption of red and processed meat and an increased risk for diabetes, while consumption of legumes (lentils, chickpeas, beans etc.) is related to a decreased risk of diabetes.
In a study published on 2006 in “Diabetes Care”, it was found that a low-fat vegan diet resulted in reduction of the dose of prescription medication for diabetes in 43% of the patients – a more significant improvement than that achieved with the diet recommended by the American Diabetes Association.
Cancer
Among vegans and vegetarians, the cancer rate is lower than that of the general population (especially prostate and colon cancer, which are among the most common types of cancer in Israel).
Consumption of red and processed meat is linked to an increase in the risk for colon cancer, and quite probably also to breast cancer. Consumption of processed meat is linked to the increased risk of stomach cancer.
In addition to the AND (formerly ADA), leading organizations emphasize the importance of plant-based nutrition in preventing cancer. In 2012, the American Cancer Society (ACS) published updated nutritional guidelines for the prevention of cancer, which recommend to: “eat a healthy diet, with an emphasis on plant foods”, and reduce the consumption of processed and red meat.
Additionally, according to the ACS, consumption of traditional soy-based foods such as tofu can reduce the risk of breast, prostate, and endometrial cancers.
In its nutritional guidelines published in 2011 entitled "The Healthy Eating Plate", Harvard University recommends to reduce the consumption of dairy products, as increased consumption is probably related to an increased risk of prostate cancer, and possibly also to ovarian cancer.
Harvard is one of the institutions leading the resolute call to incorporate more plant-based foods in daily nutrition, and also to limit the consumption of red meat while avoiding processed meat, since “eating even small quantities of these foods on a regular basis raises the risk of heart disease, diabetes, colon cancer, and weight gain”.
Nutrients in plant-based food versus animal-based food
Compared to an omnivore and even to a vegetarian diet, the vegan diet includes a higher quantity of nutrients, such as folic acid, potassium, magnesium, and dietary fibers.
Dietary fibers exist exclusively in plants, and they are known for promoting a feeling of satiety and helping to regulate blood sugar and cholesterol levels. A vegan diet contains no cholesterol at all, and is low in saturated fat. Cholesterol and saturated fat in food sources contribute to an increased level of cholesterol in the blood.
In addition to high cholesterol levels, another factor contributing to the development of atherosclerosis is the oxidation of LDL (“bad cholesterol”). Oxidation is a natural process in the body, but in excess it is a significant factor in the development of cardiovascular diseases, diabetes, cancer and more.
A vegan diet is significantly richer in antioxidants, including: vitamins C and E, flavonoids and carotenoids. In contrast, food from animal sources contains a negligible amount of antioxidants, and a high quantity of oxidizers including iron. The body can regulate the absorption of iron from plant sources according to its requirements, but it cannot regulate the absorption of iron from animal sources (HEME iron), so it is possible to reach an excess of iron, which promotes the oxidation processes, in turn related to an increase in the risk for cardiovascular diseases, diabetes and colon cancer.
To conclude, it is foreseeable that in the near future, an increasing number of health organizations will begin to unequivocally recommend a plant based diet as a strategy for the prevention and treatment of diseases.
Recently, the American care provider Kaiser Permanente published guidelines for its physicians, according to which:
“Healthy eating may be best achieved with a plant-based diet, which we define as a regimen that encourages whole, plant-based foods and discourages meats, dairy products, and eggs as well as all refined and processed foods … Physicians should consider recommending a plant-based diet to all their patients, especially those with high blood pressure, diabetes, cardiovascular diseases, or obesity."
Additional information and scientific articles by leading researchers in the field
