Scientific Update

A Review of Recent Scientific Papers Related to Vegetarianism

Vegetarian Low-Carbohydrate Diet No More Effective Than Vegetarian High-Carbohydrate Diet for Weight Loss

High-protein, low-carbohydrate diets have been promoted as weight loss diets. Typically, these diets feature high amounts of animal protein, saturated fat, and total fat; limited carbohydrate; and little fiber. Researchers wondered what would happen if they modified this type of diet to make it vegetarian; replaced the animal protein with protein from gluten, soy, nuts, vegetables, and cereals; increased the carbohydrate somewhat; replaced saturated fat sources like cheese and bacon with unsaturated fats from nuts, vegetable oils, soy, and avocado; and roughly tripled the fiber using mainly soluble fiber from oats, barley, and some vegetables. This diet is markedly different from the Atkins diet (a typical high-protein, low-carbohydrate diet), which in the early stages is reported to contain 20 grams of carbohydrate or less, approximately 28 percent of calories from protein, and approximately 55 percent of calories from fat. In contrast, the vegetarian weight loss diet, or ‘low-carbohydrate diet,’ included 130 grams of carbohydrate daily, 31 percent of calories from protein, and 43 percent of calories from fat.

Researchers wanted to see how the low-carbohydrate diet compared to a high-carbohydrate vegetarian diet based on lowfat dairy and whole grain products. They studied 47 overweight men and women with high blood LDL (bad) cholesterol levels. Subjects were assigned to either the high-carbohydrate or the low-carbohydrate diet for four weeks with calories adjusted so that each group only got approximately 60 percent of the calories they would need to maintain their weight. Weight loss was similar for both groups—approximately 81/2 pounds on average over the four weeks. This suggests that reducing the amount of carbohydrate in a vegetarian diet and increasing the protein does not improve weight loss. The low-carbohydrate diet did lead to a greater reduction in blood pressure, LDL and total cholesterol, and triglyceride levels than did the higher carbohydrate diet. Since the two diets differed in several ways, we do not know if the results seen were due to the higher protein/lower carbohydrate content of the low-carbohydrate diet, to the type of carbohydrate used, or to some other factor. Additional study is needed to see if a low-carbohydrate vegetarian diet can be used long-term for weight loss and to reduce LDL cholesterol levels.

Jenkins DJA, Wong JMW, Kendall CWC, et al. 2009. The effect of a plant-based low-carbohydrate ("Eco-Atkins") diet on body weight and blood lipid concentrations in hyperlipidemic subjects. Arch Intern Med 169:1046-54.

Medications for Vegetarians

When a British psychiatrist’s patient refused to take non-vegetarian medications, the psychiatrist contacted drug manufacturers to determine whether their products contained ingredients derived from animals. He inquired about antipsychotic, antidepressive, and antimanic medications and found out that almost three-quarters of them were indeed vegetarian. Those that were not vegetarian included medications in capsules (made from animal-derived gelatin) and medications containing animal-derived lactose and magnesium stearate. He did not ask if the products were tested on animals. Products vary from company to company and in different countries; this report was from the UK. In some instances, another company may make a vegetarian version of the medication. Changes in medication should not be made without consulting with your health care provider.

McAllister-Williams H, Ramplin S. 2009. Vegetarian psychotropics: a survey of psychotropic medications suitable for vegetarians. Hum Psychopharmacol Clin Exp 24:248-50.

British Vegetarians Have Lower Rates of Some Cancers

A recent large study from the UK examined rates of 20 different cancers in more than 60,000 British men and women. Study subjects were classified as meat-eaters, non-meat-eaters who ate fish (fish-eaters), and vegetarians. Subjects were studied for an average of 12 years. Compared to meat-eaters, vegetarians had lower rates of bladder cancer and of cancers like non-Hodgkin’s lymphoma and multiple myeloma. Vegetarians and fish-eaters had lower rates of stomach cancer. Overall, vegetarians and fish-eaters had a lower risk of cancer compared to meat-eaters. A possible explanation for the higher rates of bladder cancer and stomach cancer in meat-eaters is that nitrates found in some processed meats may increase the risk of these cancers. Mutagenic compounds and viruses in meat may partially explain the higher rates of lymphoma and myeloma in meat-eaters. This study also found higher rates of cervical cancer in both vegetarians and fish-eaters. Because of the small number of cases and the fact that the primary risk factor for cervical cancer is human papillomavirus, the researchers suspect their results are due to chance or to differences in screening for cervical cancer in different groups. Overall, the results of this study suggest that a vegetarian diet plays a role in reducing risk of some cancers.

Key TJ, Appleby PN, Spencer EA, et al. 2009. Cancer incidence in British vegetarians. Br J Cancer 101:192-97.

Four Lifestyle Factors Appear Important For Reducing Risk of Chronic Diseases

Four factors appear to be very important in reducing the risk of type 2 diabetes, heart disease, cancer, and stroke. What are they? Never smoking, not being obese (BMI under 30), being physically active for 31/2 hours or more a week, and eating fruits, vegetables, whole grains, and little or no red meat.

A study of more than 23,000 German adults over an 8-year period was used to show just how important these factors are. At the start of the study, participants were given a score of 0 or 1 in each category (1=never smoked, 0=current or former smoker, etc.). Subjects could have a total score of 0-4, with 4 being the best score. Subjects with a score of 4 had a 78 percent lower risk of having any of the chronic diseases compared with subjects with a score of 0. Those with a score of 4 had a 93 percent lower risk of having type 2 diabetes, 81 percent lower risk of heart attack, 50 percent lower risk of stroke, and 36 percent lower risk of cancer compared with subjects with a score of 0. Subjects with a score of 1, 2, or 3 were between those with a score of 0 and those with a score of 4 in terms of their risk of these diseases. Having only one healthy behavior as compared to none still cut the risk of chronic disease in half.

How would you score? Have you never smoked? Do you have a healthy weight? Are you physically active at least 31/2 hours a week? Is your diet plant-based with little or no red meat? If you can answer yes to all of these questions, you have markedly reduced your risk of a number of health problems.

Ford ES, Bergmann MM, Kroger J, et al. 2009. Healthy living is the best revenge. Arch Intern Med 169:1355-62.

The American Dietetic Association Publishes a New Position Paper on Vegetarian Diets

The American Dietetic Association (ADA) published their updated position on vegetarian diets in the July 2009 Journal of the American Dietetic Association. The ADA’s position on vegetarian diets is, "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 life cycle, including pregnancy, lactation, infancy, childhood, and adolescence, and for athletes." Although in the past the ADA position paper has included support for vegetarian diets throughout life, this is the first time this endorsement has appeared in the actual position statement.

The paper also includes information about key nutrients for vegetarians, health benefits of vegetarian diets, and the role of vegetarian diets in prevention and treatment of chronic diseases, such as obesity, heart disease, high blood pressure, diabetes, and cancer. This paper was developed over a 2-year period and is based on the most recent research available. It is a very complete source of information for the media, health care professionals, and others with questions about vegetarianism. The complete position paper is available on the ADA’s website:

Craig WJ, Mangels AR. 2009. Position of the American Dietetic Association: Vegetarian diets. J Am Diet Assoc 109:1266-82.