Scientific Update
A Review of Recent Scientific Papers Related to Vegetarianism
By Reed Mangels, PhD, RD, FADA
German Vegans Are Leaner But Have Low Calcium and Vitamin B12 Intakes from Diet
Results of a large study of German vegans were recently published. The subjects were divided into two groups - those who never ate any animal-derived foods (strict vegans) and those who ate very small amounts of eggs and dairy products (so-called moderate vegans). A total of 154 people ranging in age from 22 to 76 years were studied. Strict vegans tended to be vegans for ethical reasons, while moderate vegans reported health reasons as their main motivation. Both groups had low Body Mass Indexes (BMIs), which suggests that most were lean rather than overweight. The researchers reported only the amounts of vitamins and minerals that subjects got from food; supplements were not included.
Without considering supplements, intakes of most nutrients were at or above current recommendations, although more than 70 percent had low calcium intakes and more than 90 percent of subjects had vitamin B12 intakes that were below recommendations. Iodine intakes also were low. Some subjects’ intakes of calcium and vitamin B12 may have been higher if supplements were included in the analysis. The authors also noted the study subjects’ very low use of alcohol and tobacco.
Waldmann A, Koschizke JW, Leitzmann C, et al. 2003. Dietary intakes and lifestyle factors of a vegan population in Germany: results from the German Vegan Study. Eur J Clin Nutr 57:947-55.
Whole Grains, Fruits, and Vegetables: A Key Part of a Health-Promoting Diet
U.S. adults don’t do very well when it comes to eating whole grains, fruits, and vegetables. The average adult only eats one serving of whole grains daily, and only 8 percent of U.S. adults eat at least three servings of whole grains daily. The average intake of fruits and vegetables is 3.4 servings per day with fewer than a quarter of U.S. adults eating the recommended five-a-day. Vegetarians tend to eat more fruits, vegetables, and whole grains, and some have speculated that this explains why vegetarians have lower rates of heart disease and other chronic diseases.
A recent large (15,792 participants) study looked at the amounts of fruits, vegetables, and whole grains U.S. adults ate and looked for connections between their diets and the occurrence of certain diseases. Not surprisingly, those people who ate more whole grains had a lower total mortality (they were less likely to die) and a lower risk of heart disease. Those who ate more fruits and vegetables also had a lower total mortality. African-Americans who ate more fruits and vegetables were less likely to have heart disease than other African-Americans, but this association was not seen in whites. Intakes of whole grains, fruits, and vegetables did not seem to affect the risk of stroke. This report provides more support for recommendations to eat more whole grains, fruits, and vegetables - in other words, a more plant-based diet.
Steffen LM, Jacobs DR, Jr, Stevens J, et al. 2003. Associations of whole-grain, refined-grain, and fruit and vegetable consumption with risks of all-cause mortality and incident coronary artery disease and ischemic stroke: the Atherosclerosis Risk in Communities (ARIC) Study. Am J Clin Nutr 78:383-90.
Diet and Ovarian Cancer: Can a Plant-Based Diet Reduce Risk?
The American Cancer Society estimates that there will be 25,000 new cases of ovarian cancer in the U.S. in 2003. This type of cancer is difficult to detect and causes more deaths than any other cancer of the female reproductive system. A number of risk factors for this disease are known, including never having children and using hormone replacement therapy. Diet may also play a role because of its effects on hormone levels. A study of more than 800 women, 124 of whom had ovarian cancer, found that lower risk of developing cancer of the ovaries was associated with higher intakes of fiber, carotenoids, vegetables, and other substances found in vegetables, like lignans and stigmasterol. The authors of this study say that their results support the hypothesis that a plant-based diet may be important in reducing the risk of hormone-related cancers like ovarian cancer.
McCann SE, Freudenheim JL, Marshall JR, Graham S. 2003. Risk of human ovarian cancer is related to dietary intake of selected nutrients, phytochemicals and food groups. J Nutr 133:1937-42.
Vitamin B12 Status of Vegetarians
A recent study of vegetarians used various blood tests to measure vitamin B12 status. One of the tests, the measurement of blood levels of holotranscobalamin II, measures the amount of the protein that carries vitamin B12 in the blood. Low levels of this indicate an early stage of vitamin B12 depletion. Another test, blood homocysteine levels, is used to check for a later stage of vitamin B12 depletion. Study subjects included 66 lacto or lacto-ovo vegetarians, 29 vegans, and 79 non-vegetarians. An early stage of vitamin B12 deficiency, indicated by low blood levels of holotranscobalamin II, was seen in as many as three-fourths of the lacto or lacto-ovo vegetarians and 90 percent of the vegans, but only 11 percent of the non-vegetarians. Blood homocysteine levels were abnormally high in 38 percent of lacto or lacto-ovo vegetarians, 67 percent of vegans, and 16 percent of non-vegetarians. Few details were available on the use of supplements of vitamin B12 by study subjects.
A vitamin B12 deficiency can have serious consequences. The results of this study point to the importance of having reliable, daily sources of vitamin B12. For more information about vitamin B12, see the VRG website.
Herrmann W, Schorr H, Obeid R, et al. 2003. Vitamin B12 status, particularly holotranscobalamin II and methylmalonic acid concentrations, and hyperhomocysteinemia in vegetarians. Am J Clin Nutr 78:131-6.
Iron is Well-Absorbed from Soybeans
Soybeans are a major source of iron for many vegetarians and for many people worldwide. Questions have been raised about how well the iron from soybeans is absorbed. In other words, even if soybeans are high in iron, are we able to absorb and use that iron? Eighteen women with marginal iron deficiency were fed meals containing soybeans. Iron absorption was measured. The iron in the soybeans appeared to be well-absorbed, suggesting that soybeans can be a good source of iron for people with a marginal deficiency.
Murray-Kolb LE, Welch R, Theil EC, Beard JL. 2003. Women with low iron stores absorb iron from soybeans. Am J Clin Nutr 77:180-4.
Organic versus Conventional Foods for Children
One of the ways that children are exposed to potentially harmful pesticides is through the foods they eat. When children’s diets are compared to adults’ diets, we often see that children eat more foods like fresh fruits, fresh vegetables, and juices that contain higher levels of pesticide residues. These foods are an important part of children’s diets and their use should be encouraged. Some parents choose to use organic foods as much as possible.
A recent study examined differences in pesticide residue levels in children’s urine to see if their diet made a difference. Thirty-nine preschoolers in Seattle, Washington, were studied. Parents kept a record of the foods their children ate. If 75 percent or more of the juice, fruits, and vegetables eaten by a child were identified as organic, he or she was classified as an Organic eater. If 75 percent or more of the juice, fruits, and vegetables were conventionally produced, a child was classified as a Conventional eater. Conventional eaters had markedly higher levels of pesticide residue in their urine than did organic eaters. This suggests that, when possible, organic produce should be used.
Curl CL, Fenske RA, Elgethun K. 2003. Organo-phosphorus pesticide exposure of urban and suburban preschool children with organic and conventional diets. Environ Health Perspect 111:377-82.
