Scientific Update

A Review of Recent Scientific Papers Related to Vegetarianism

by Reed Mangels PhD, RD, FADA

Choices: How Your Diet, Exercise, and Other Behaviors Can Affect the Length and Quality of Your Life

Many factors affect how long and how well a person lives. Can we make conscious choices to improve the quality and span of our lives? A recent study suggests that it is possible. More than 34,000 Seventh-day Adventists living in California were studied for 12 years. Seventh-day Adventists are less likely to smoke and may exercise more than the typical person in the US. Many follow a vegetarian diet; nearly 30% of the subjects were vegetarians, and another 20% described themselves as semi-vegetarian (ate meat fewer than one time per week but more than once per month). At birth, an infant who would grow up to be a California Adventist male would be expected to live 78.5 years, a female California Adventist, 82.3 years. If the California Adventist was also vegetarian, life expectancy at birth increased to 80.2 years for men and 84.8 years for women. Compare this to a US male whose life expectancy at birth is 73 years and a US female who can expect to live 79.7 years.

Let's look at it another way. Say you are a typical American woman, age 65. If you are truly average, you can expect to live 19.1 more years—to age 84. If you are a typical vegetarian Adventist, you can expect to live 22.6 more years—almost to age 88. A typical American male, age 65, can expect to live almost 15 more years—to age 80. A vegetarian Adventist male can expect to live 20 more years, to age 85.

This study did not examine quality of life, but other studies have shown that vegetarian Adventists take less medicine and have fewer hospital stays than do non-vegetarians. They also have been shown to have lower rates of several chronic diseases that can affect the quality of life.

Yes, it does appear that choices about diet, exercise, smoking, and other factors can help one to live longer and with less risk of disease.

Fraser GB, Shavlik DJ. 2001. Ten years of life. Is it a matter of choice? Arch Intern Med 161:1645-2011.

Eating Behaviors of Self-Described Vegetarian Women

The term “vegetarian” can mean different things to different people. Canadian researchers conducted a study of women who called themselves “vegetarian” to see what their eating behaviors were. The researchers also wanted to see how vegetarian dietary practices change over time and to evaluate how self-described vegetarians feel about meat and dairy products.

Almost 200 women between the ages of 18 and 50 participated in the study. Ninety said they were vegetarian, 35 were former vegetarians, and 68 had never been vegetarian. Of the so-called vegetarians, 6 were vegan, 11 used dairy products but not eggs, 22 used dairy products and eggs, and 51 ate fish or chicken occasionally. This suggests that less than half of the group who identified themselves as vegetarians regularly ate diets that fit the standard definition of vegetarian (no meat, fish, or fowl).

Current “vegetarians” reported eating fewer animal products than they did when they first became vegetarian (true for 63% of self-described vegetarians). They also said that they planned to eat fewer dairy products in the coming year (20% of vegetarians), less fish (5%), and more fruits and vegetables (11%).

As would be expected, more vegetarians expressed concerns about meat than did non-vegetarians. Concerns included “toxins” in animal fat, unnatural hormones and antibiotics in red meat, and the amount of fat in red meat. Self-described vegetarians were more likely than non-vegetarians to agree with the statement that dairy products are not needed by adults. They were more likely to believe that dairy products contain unnatural hormones and antibiotics, and less likely to agree that a diet with dairy is healthier than a diet without dairy products.

These results suggest that self-described vegetarians who may eat fish and/or chicken are sympathetic towards a vegetarian diet and may be interested in reducing their use of animal products.

Barr SI, Chapman GE. 2002. Perception and practices of self-defined current vegetarian, former vegetarian, and nonvegetarian women. J Am Diet Assoc 102:354-360.

Eating Disorders in Teenage Vegetarians: Cause for Concern?

A recent study from the University of Minnesota raised the concern that teen vegetarians are more likely to have eating disorders than non-vegetarians. This study, which surveyed nearly 5,000 middle- and high-school students, found that almost 6% described themselves as being vegetarian or not eating red meat. More than half of the self-described “vegetarians” ate chicken, so the description of their diet as “vegetarian” is misleading. Teens who described themselves as vegetarian were more weight-conscious and more likely to have been told they had an eating disorder, including conditions like anorexia nervosa and bulimia. These teens reported that their main reason for using a vegetarian or partial vegetarian diet was as a weight control method. Unfortunately, they were also practicing other behaviors which were not as healthful as a vegetarian diet can be, including using diet pills, abusing laxatives, and self-inducing vomiting after meals.

Can we say that these teens had eating disorders as a result of their vegetarian diet? No, we can't. It seems more likely that these teens already had a number of issues with food and body weight and simply chose a vegetarian or partial vegetarian diet as one more way to restrict their food intake. This study shows that it is important to carefully define the term “vegetarian,” since the study's results made it appear that vegetarians were at increased risk for eating disorders when, indeed, only half of these “vegetarians” really were vegetarian. Another study has shown that only 6% of teens with anorexia nervosa chose to follow a vegetarian diet before the onset of their eating disorder. Many more became vegetarian after the onset of their eating disorder.

Perry CL, McGuire MT, Newmark-Sztainer D, Story M. 2001. Characteristics of vegetarian adolescents in a multiethnic urban population. J Adolesc Health 29:406-416.

Mortality in British Vegetarians

Vegetarians were compared with health-conscious but non-vegetarian subjects in a study from the United Kingdom. More than 8,000 vegetarians were studied over an average of 20 years and found to have low mortality compared with that of the general population. The vegetarians were also compared with nearly 12,000 non-vegetarians who were considered to be health-conscious. Somewhat surprisingly, the non-vegetarians had death rates that were similar to vegetarians, suggesting that factors other than avoidance of meat and fish may influence mortality. These factors include a low prevalence of smoking, a generally high socio-economic status, and possibly a higher intake of fruits and vegetables. Vegetarians did appear to have lower rates of death from heart disease. However, vegetarians had higher rates of death from breast cancer. This may be due to fewer births in the vegetarian women, a factor that would be expected to increase risk of breast cancer. Additional research is needed to determine if there are other dietary factors typical of both vegetarians and health-conscious non-vegetarians that led to low mortality in both groups.

Appleby PN, Key TJ, Thorogood M, et al. 2002. Mortality in British vegetarians. Public Health Nutr 5:29-36.

Which Plants Give Us the Most Antioxidants?

Antioxidants play an important role in our health by helping to protect our bodies from damage that can lead to cancer, heart disease, and other chronic diseases. Some well-known antioxidants are vitamins E and C and the carotenoids, found in fruits, vegetables, and whole grains. These foods also contain a variety of other antioxidants. Norwegian researchers assessed the total antioxidant content of dietary plants worldwide and found a more than 1,000-fold difference in the amount of dietary antioxidants in different plants.

Overall, the plants that contain the most antioxidants (and that are widely available in the US and Canada) are pomegranates, berries (including strawberries, blueberries, and raspberries), walnuts, sunflower seeds, and ginger. Other plant foods with high antioxidant levels include red beets, chili peppers, kale, red cabbage, bell peppers, parsley, artichokes, currants, fava beans, dried apricots, and prunes. These results certainly support recommendations to eat a varied diet containing generous amounts of fruits and vegetables.

Halvorsen BL, Holte K, Myhrstad MCW, et al. 2002. A systematic screening of total antioxidants in dietary plants. J Nutr 132:461-471.