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Vegetarian Journal 2002 Issue 4

Scientific Update

Review of Recent Scientific Papers Related to Vegetarianism

By Reed Mangels, PhD, RD, FADA

High Fiber Diet Without the Worry of Discomfort

Contributed by Erin M. Crandell, VRG Intern and University of Michigan MPH and RD Candidate

Health professionals are telling you to include more fiber in your diet. Among other advantages, increasing your fiber intake can decrease your risk for some forms of cancer, decrease bad cholesterol levels while maintaining good cholesterol levels, and reduce the risk for heart disease. You may be worried that this recommendation may cause you gastrointestinal discomfort. Good news! According to this new study, the authors conclude you can rest easy and increase your fiber intake without the worries of discomfort.

Few studies have examined the effect of high dietary fiber intake for extended periods of time on gastrointestinal discomfort. In an effort to gain a better understanding of these effects, a recent scientific report examined more than 1,200 women who consumed varying amounts of fiber and maintained this diet for one year. The women were selected from the Women's Healthy Eating and Living (WHEL) Study, which looked at the effects of diet on breast cancer. Women were divided into two groups: the first group increased their fiber intake, and the second group maintained their original fiber intake. Women in the first group were encouraged to increase their fiber consumption to 30 grams per day by consuming vegetables, fruits, legumes, and whole grain products. Women in the second group were encouraged to eat at least 5 servings of fruits and vegetables per day. Over the course of the study, fiber intake was increased only in the first group. Both groups were asked to complete a questionnaire related to gastrointestinal symptoms such as bloating/gas, constipation, diarrhea, heartburn, and upset stomach. After each four-month time interval, the participants rated the level of these symptoms using four categories: "symptoms did not occur," "mild," "moderate," or "severe." "Mild" was defined as symptoms did not interfere with usual activities, "moderate" included symptoms that interfered somewhat with usual activity, and "severe" was classified as so bothersome that usual activities could not be performed. Analysis was carried out based on classification in these groups and fiber consumption.

After the one-year study period and analysis, results indicated that higher dietary fiber consumption is not associated with gastrointestinal discomfort. Participants who consumed a higher fiber diet (more than 35 grams of fiber daily) reported only 40% of the constipation symptoms as compared with the women who consumed a lower fiber diet (35 grams or fewer per day). In addition, participants who consumed a higher fiber diet reported only about 70% of the heartburn symptoms as compared to those on the lower fiber diet. Fiber intake did not appear to be associated with symptoms of diarrhea, bloating, gas, or upset stomach.

Based on this study, in combination with other studies reviewed in the article, the authors concluded that high fiber consumption is not associated with any adverse gastrointestinal effects. Listen to your health professional's pleas and increase your fiber intake without the worries!

McEligot AJ, Gilpin EA, et al. 2002. High dietary fiber consumption is not associated with gastrointestinal discomfort in a diet intervention trial. J Am Diet Assoc 102(4):549-551.

Good News About Vegetarian Diets for Teens

Adult vegetarians tend to have lower risks for many chronic diseases, perhaps because of their healthier diets. Do teenage vegetarians also have healthier diets? This was the question that researchers at the University of Minnesota recently attempted to answer. They studied more than 4,500 teens from the major urban school districts in Minnesota. Although 5.8% reported that they were vegetarian, more than half of them also reported eating chicken and/or fish. Actually, 1.9% were truly vegetarian, which agrees with the results of The VRG's poll showing that about 2% of teens are vegetarian ( Teens who followed a vegetarian diet were more likely to meet recommendations for total fat, saturated fat, and number of servings of fruits and vegetables as compared to non-vegetarians. Teens who said they were vegetarian (whether or not they actually were) had higher intakes of iron, vitamin A, fiber, and diet soda, and lower intakes of vitamin B12, cholesterol, and fast food. Most teens, whether they were vegetarian or not, did not meet recommendations for calcium. The authors concluded, "rather than viewing adolescent vegetarianism as a difficult phase or fad, the dietary pattern could be viewed as a healthy alternative to the traditional American meat-based diet." They went on to say that vegetarian diets in adolescence could lead to lifelong health-promoting dietary practices.

Perry CL, McGuire MT, Neumark-Sztainer D, et al. 2002. Adolescent vegetarians. How well do their dietary patterns meet the Healthy People 2010 objectives? Arch Pediatr Adolesc Med 156:431-437.

New Food Guide Pyramid for Vegetarians

The USDA Food Guide Pyramid was developed to help people plan a healthy diet. It can be used to plan vegetarian diets that include dairy products, but cannot accommodate a vegan diet. Because of this problem, and for other reasons, several groups have developed food guide pyramids specifically for vegetarians. Researchers at Arizona State University created one such pyramid. They also checked to see if it was possible to plan a nutritionally adequate diet using this pyramid. They found that their pyramid could be used to plan both vegan and lacto-vegetarian diets at several different calorie levels. Their Vegetarian Food Pyramid calls for 6-10 servings of breads, pasta, and rice; 2-3 servings of green leafy vegetables; 2-4 servings of other vegetables; 1-2 servings of dried fruit; 1-2 servings of other fruits; 3 servings of dairy products or fortified soymilk; 2-3 servings of beans, meat alternatives, tofu, tempeh, eggs, or peanut butter; 1-2 servings of nuts and seeds; and 2-3 teaspoons of olive, flaxseed, canola, or walnut oil.

Examples of other food guides for vegetarians and vegans can be found at Loma Linda University, Oldways Preservation & Exchange Trust, Vesanto Melina, RD, and American Dietetic Association.

Venti CA, Johnston CS. 2002. Modified food guide pyramid for lactovegetarians and vegans. J Nutr 132:1050-2011.

Key Factors for Mental Function in Older People

Dietary factors may have an effect on conditions like memory loss, Alzheimer's disease, and dementia in older people. Scottish researchers compared two groups, one with participants between 76-78 years and one 61-63 years. The older group had higher levels of a substance called homocysteine in their blood (see the Nutrition Hotline on page 2, for information about homocysteine); this suggests that their diets did not have enough vitamin B12 and/or folate. In the older group, subjects with higher levels of homocysteine did less well on some tests of mental function. It is certainly possible that the homocysteine itself is toxic to cells in the nervous system. It is also possible that high levels of homocysteine indicate a lack of vitamin B12 and/or folate that could affect brain function. Older people can have difficulty absorbing vitamin B12 so those age 51 years or older should use vitamin B12-fortified foods or supplements to meet most of their requirements, since the vitamin B12 in fortified foods and supplements is usually well absorbed.

Duthie SJ, Whalley LJ, Collins AR, et al. 2002. Homocysteine, B vitamin status, and cognitive function in the elderly. Am J Clin Nutr 75:908-913.

Swedish Vegans

In Sweden, approximately 0.1% of older teens (ages 16-20) are vegan. Swedish researchers were curious about the diets of vegan teens in their country so they studied 30 vegans and 30 non-vegetarians. The primary motivation for following a vegan diet was reported to be ethical reasons. Male vegans weighed less than male non-vegetarians, while there was no difference in weight among the females. Vegans ate more vegetables and legumes and were more likely to use supplements. They also had lower intakes of fat, saturated fat, and cholesterol and higher intakes of fiber, folate, and vitamin C. Calcium intakes of vegans were below recommendations, even when supplemental calcium was included. Iron status was similar between the two groups. Two vegans had low intakes of vitamin B12 and low blood vitamin B12 levels. This study illustrates the many positive features of vegan diets while showing the need for attention to key nutrients like calcium and vitamin B12.

Larsson CL, Johansson GK. 2002. Dietary intake and nutritional status of young vegans and omnivores in Sweden. Am J Clin Nutr 76:100-106.

Excerpts from the 2002 Issue 4:

The Vegetarian Journal published here is not the complete issue, but these are excerpts from the published magazine. Anyone who wishes to see everything should subscribe to the magazine.

Thanks to volunteer Stephanie Schueler for converting this article to HTML.

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