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VRG > Vegetarian Journal > 2006 Issue 2 > Scientific Update

Scientific Update

A Review of Recent Scientific Papers Related to Vegetarianism

By Reed Mangels, PhD, RD, FADA

Vegan Teens in Sweden Eat
More Fruits and Vegetables

Sweden, like the United States, recommends that people eat generous amounts of fruits and vegetables. In Sweden, the recommendation is 500 grams (approximately 17 ounces) of fruits, vegetables, and berries daily. A study comparing Swedish vegan teens to non-vegetarian teens found that 21 of 30 vegans met this recommendation, while only one non-vegetarian did so. While the groups were similar in terms of the amount of fruit and berries that they ate, the vegans ate significantly more vegetables than non-vegetarians did. Besides eating more servings from the fruit and vegetable group, the vegans also ate a greater variety of foods and consumed less candy and chocolate. Vegans used supplements as their main source for vitamin B₁₂, calcium, zinc, and selenium, although they did get some calcium from vegetables and some zinc and selenium from grains.

Larsson CL, Johansson GK. 2005.: Young Swedish vegans have different sources of nutrients than young omnivores. J Am Diet Assoc 105:1438-41.

Lifelong Vegetarians Are Not Different in Height or Weight From People Who Became Vegetarian Later in Life

A large study in the United Kingdom investigated whether people who are lifelong vegetarians are more likely to be shorter or lighter in weight than people who become vegetarians as adults. More than 350 lifelong vegetarians, 11,000 people who became vegetarian at age 20 years or older, and 29,000 non-vegetarians were surveyed. There were only two lifelong vegans, and they were included with the vegetarian group. Average height, weight, and Body Mass Index (BMI) were not significantly different between lifelong vegetarians and those who became vegetarian as adults. Results were similar for men and women. There was also no significant difference in age at menarche among the groups. Non-vegetarians were heavier than vegetarians and had higher BMIs. This study suggests that the growth of lifelong vegetarians is similar to the growth of those who were not vegetarians as children and that maturation, as indicated by age at menarche, is not affected by a vegetarian diet. It also supports the findings of other studies that show that, on average, vegetarians are slimmer than non-vegetarians.

Rosell MS, Appleby PN, Key T. 2005.: Height, age at menarche, body weight and body mass index in lifelong vegetarians. Public Health Nutr 8:870-75.

Omega-3 Fatty Acids for Vegetarians

Two omega-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are found mainly in oily fish. These fats have been linked to a reduced risk of heart disease and stroke. Vegetarian diets contain low levels of EPA and DHA, mainly from dairy products and eggs; vegan diets do not normally contain EPA or DHA. Our bodies can make small amounts of EPA and DHA from another fat, alpha-linolenic acid that is found in flax seeds and flax seed oil and, to a lesser extent, in canola oil and soy products. This production is very limited, however. A recent study examined the levels of EPA and DHA in the blood of British vegetarian, vegan, and non-vegetarian men. ¹ Approximately 200 men were in each group. EPA and DHA levels were lower in the vegetarians than in the meat-eaters and were lower in the vegans than in the vegetarians. Is this cause for concern? Possibly. Low blood levels of DHA and EPA have been associated with heart disease, stroke, and Alzheimer's disease. Conversely, vegetarians have a lower risk of heart disease than meat-eaters. Vegetarians can obtain DHA from microalgae. A German study gave 104 vegetarians a supplement containing either DHA-rich oil from microalgae or olive oil for 8 weeks. ² At the beginning of the study, none of the subjects had what is considered to be a desirable level of DHA + EPA in their blood. Low levels were seen even in subjects who met or exceeded the recommendations for alpha-linolenic acid, which is used to make DHA and EPA. After using supplements, 69 percent of the group receiving the DHA had a desirable level of DHA + EPA. DHA supplements derived from microalgae can help vegetarians achieve desirable levels of DHA + EPA.

¹ Rosell MS, Lloyd-Wright Zechariah, Appleby PN, et al. 2005.: Long-chain n-3 polyunsaturated fatty acids in plasma in British meat-eating, vegetarian, and vegan men. Am J Clin Nutr 82:327-34.
² Geppert J, Kraft V, Demmelmair H, Koletzko B. 2005.: Docosahexaenoic acid supplementation in vegetarians effectively increases omega-3 index: a randomized trial. Lipids 40:807-14.

A Very Lowfat Vegan Diet Meets Nutrient Needs of Older Men

Dean Ornish, MD, is known for his investigations that use a very lowfat near-vegan diet and other lifestyle changes to reverse heart disease. He has recently turned his attention to the treatment of prostate cancer. Despite the widespread acceptance of plant-based diets, there are still people who question whether a very lowfat vegan diet can be nutritionally adequate. Ornish and co-workers recently addressed this question when they studied 39 men whose average age was 65 years and who had been diagnosed with prostate cancer. The men agreed to follow a very lowfat vegan diet, exercise, and participate in a support group. The men also used a fortified soy protein powder daily because of the possible role of soy in inhibiting growth of prostate cancer. After six months, the men's diets were analyzed and found to meet or exceed recommendations for all nutrients except for vitamin D. The fortified soy protein was the main source of calcium and vitamin B₁₂. These results show that a very lowfat vegan diet can meet recommendations for most nutrients.

Dunn-Emke SR, Weidner G, Pettengill EB, et al. 2005.: Nutrient adequacy of a very low-fat vegan diet. J Am Diet Assoc 105:1442-46.

Lowfat Vegan Diet Promotes Weight Loss

What would happen if overweight, older women were placed on a lowfat vegan diet? That's what Neal Barnard, MD, and co-researchers wondered. The team recruited 64 overweight women and randomly assigned them to either a lowfat (10 percent of calories from fat) vegan diet or the sort of diet that is commonly recommended for people with high cholesterol levels (<30 percent calories from fat, low saturated fat, and cholesterol) for 14 weeks. The women were not told to reduce their calories and were allowed to prepare their own meals. They were asked not to change their usual exercise habits. The women on the vegan diet reduced protein, fat, and cholesterol intake and increased their fiber intake. Both groups lost weight, but the group on the vegan diet lost more, close to 13 pounds compared to 8 pounds lost in the other group. The group eating the vegan diet also had a greater reduction in waist circumference. These results show that a lowfat vegan diet can be useful for weight loss.

Barnard ND, Scialli AR, Turner-McGrievy G, et al. 2005.: The effects of a low-fat, plant-based dietary intervention on body weight, metabolism, and insulin sensitivity. Am J Med 118:991-97.

Processed Meat and Red Meat Increase Risk of Pancreatic Cancer

Although cancer of the pancreas is not common, it is a serious disease. It accounts for only about 2 percent of new cancer cases in the United States, but it is the fourth leading cause of cancer deaths. Factors such as cigarette smoking, obesity, and a sedentary lifestyle are known to increase risk of pancreatic cancer. A recent study suggests a link between diet and risk of pancreatic cancer. More than 190,000 people in California and Hawaii were studied for seven years. Those subjects who ate the most processed meat, foods such as lunch meat and hot dogs, had a 68 percent greater risk of having pancreatic cancer compared to those who ate the least processed meat. Those eating the most red meat, including beef, pork, and lamb, had a 50 percent greater risk of pancreatic cancer compared to those eating the least red meat. These results, in conjunction with other studies with similar findings, provide yet another reason to avoid meat.

Nothlings U, Wilkens LR, Murphy SP, et al. 2005.: Meat and fat intake as risk factors for pancreatic cancer: The Multiethnic Cohort Study. J Nat Cancer Inst 97:1458-65.