Scientific Update
A Review of Recent Scientific Papers Related to Vegetarianism
By Reed Mangels, PhD, RD, FADA
Whole Grains Reduce Risk of Heart Disease
A recent study added more support to the important role of whole grains in health-promoting diets. The Health Professionals Follow-Up Study asked more than 40,000 male dentists, veterinarians, pharmacists, and other health professionals about their use of whole grains. Those subjects who had the highest intake of whole grains had a markedly lower risk of heart disease than those with the lowest intake. Cold breakfast cereals were the largest source of whole grains, followed by brown rice, dark bread, and cooked oats. Whole grains contain many substances, including fiber, vitamins, minerals, and phytochemicals, that may contribute to the reduction of heart disease risk. These findings, along with other studies showing that whole grains can reduce the risk of obesity and diabetes, point to the important role of whole grains in our diets.
- Jensen MK, Koh-Banerjee P, Hu FB, et al. 2004.
- Intakes of whole grains, bran, and germ and the risk of coronary heart disease in men. Am J Clin Nutr 80:1492-99.
Vitamin B12 in Pregnancy
Adequate vitamin B12 intake is important in pregnancy. While vegan women often use fortified foods as their main source of vitamin B12, women who follow a lacto-ovo vegetarian diet may choose dairy products as their primary source of vitamin B12. Dairy products can provide an adequate amount of this vitamin, but simply drinking a cup or two of cow’s milk daily may not be enough to meet B12 needs in pregnancy.
Researchers in Germany and The Netherlands studied more than 100 women—approximately one-fourth followed a lacto-ovo vegetarian diet, 40 percent ate less than 10 ounces of meat per week, and 40 percent ate a standard diet (>10 ounces of meat per week). Vitamin B12 intake was lowest in the vegetarians, followed by the low meat-eaters, while the women eating a standard diet had the highest. Approximately 60 percent of the vegetarian women met recommendations for vitamin B12 using a combination of dietary sources (mainly milk and dairy products) and supplements, but 40 percent of women had vitamin B12 intakes below recommendations. Dietary intake was reflected in blood vitamin B12 levels; close to 40 percent of the vegetarian women, 9 percent of the low meat-eaters, and 3 percent of the meat-eaters had low blood vitamin B12 levels at some point in their pregnancy.
Low blood vitamin B12 levels were only found in women who had a vitamin B12 intake of less than 4 micrograms per day. The recommended daily allowance (RDA) for pregnancy is 2.6 micrograms. Thus, even women whose dietary vitamin B12 intake met recommendations could still have low blood vitamin B12 levels. These results suggest that the RDA for vitamin B12 in pregnancy is too low. Pregnant women should be aware of good sources of vitamin B12. Good sources include foods fortified with vitamin B12 like fortified soymilk (0.8-3.2 micrograms per cup), fortified breakfast cereals (0.6-6 micrograms per ounce), and Vegetarian Support Formula nutritional yeast (1.5 micrograms in 1 Tablespoon mini-flakes).
- Koebnick C, Hoffmann I, Dagnelie PC, et al. 2004.
- Long-term ovo-lacto vegetarian diet impairs vitamin B12 status in pregnant women. J Nutr 134:3319-26.
Dietary Treatment for High Blood Cholesterol Levels
Statins are a type of drugs that are widely used to treat high blood cholesterol levels and reduce heart disease. A new study suggests that dietary changes can have a cholesterol-lowering effect that is similar to statins. David Jenkins and other researchers at the University of Toronto studied 34 men and women who had high blood lipid levels. The subjects were placed on three different diets. For one month, they were on a very low saturated fat diet. Another month, they were on the same diet, plus statin medication. For another month, they ate a vegan diet high in soy protein, almonds, and viscous fibers from oats, barley, psyllium, eggplant, and okra. The subjects had an average decrease in LDL (bad) cholesterol of 8.5 percent on the low saturated fat diet, 33 percent on the statin regimen, and 30 percent on the vegan diet. One-fourth of the participants had their lowest LDL-cholesterol levels while they were on the vegan diet. These results suggest that a number of cholesterol-lowering foods, in conjunction with a very low saturated fat vegan diet, can have a significant effect on blood lipid levels. Drug therapy is not without risk; perhaps more people should be advised of dietary changes that can lower blood lipid levels.
- Jenkins DJA, Kendall CWC, Marchie A, et al. 2005.
- Direct comparison of a dietary portfolio of cholesterol-lowering foods with a statin in hypercholesterolemic participants. Am J Clin Nutr 81:380-87.
Red and Processed Meat Linked to Colon Cancer
More than 50,000 Americans die each year from colon cancer. Is there a dietary connection? Probably. Researchers with the American Cancer Society obtained diet information that more than 150,000 American adults provided in 1982 and in 1992. Intakes of red and processed meat averaged 17 ounces weekly in men and 10.5 ounces weekly in women. Subjects who ate the most processed meat in both 1982 and 1992 had a higher risk of colon cancer than those eating less processed meat. Those eating the most red meat and the least poultry and fish also had a significantly increased risk of colon cancer. These results agree with studies showing that vegetarians are at lower risk for colon cancer than are meat-eaters. This study, in conjunction with other studies showing the same link between red meat and colon cancer as well as a link between red meat and diabetes (See Vegetarian Journal, Issue 2, 2005.), raise significant concerns about Americans’ increasing consumption of red and processed meats.
- Chao A, Thun MJ, Connell CJ, et al. 2005.
- Meat consumption and risk of colorectal cancer. JAMA 293:172-82.
Dietary Guidelines, 2005
Dietary Guidelines for Americans is a statement of current federal policy on the role of dietary factors in health promotion and disease prevention. The USDA and the Department of Health and Human Services issue Dietary Guidelines every five years. The latest edition, issued in January 2005, includes changes that will impact the Food Guide Pyramid. One of the most significant changes is that dried beans are given a much fairer treatment. In the past, you had to eat 1-1/2 cups of cooked dried beans to equal a 2 to 3 ounce serving of meat. The latest edition of Dietary Guidelines more realistically calls 1/2 to 3/4 cup of cooked beans equivalent to a serving of meat. In fact, the guidelines state that 1-1/2 ounces of nuts and 2/3 cup of legumes can take the place of the 5.5 ounces of meat that typically is included in a 2000 calorie diet. Changes like these make it obvious that it is easy to follow a vegetarian diet.
While the guidelines acknowledge that Americans consume too many saturated and trans fats, cholesterol, added sugars, and salt, there is little identification of specific foods (like meats) that should be avoided. In an ideal world, the Dietary Guidelines would clearly state that vegetarian diets have significant health benefits, but that didn’t happen in this edition.
Despite these limitations, these latest Guidelines definitely have some advantages over previous recommendations. The Executive Summary states, “It is important to incorporate the food preferences of different racial/ethnic groups, vegetarians, and other groups when planning diets and developing educational programs and materials.” This language could be used to push for more vegetarian options in the School Lunch Program and other federally supported meal programs. Recommendations call for increased use of fruits, vegetables, and whole grains with a total of 2 cups of fruit and 21/2 cups of vegetables per day recommended for someone typically eating 2000 calories. Additionally, specific fruits and vegetables (dark green vegetables, orange fruits and vegetables, legumes, etc.) are promoted rather than simply encouraging people to eat more fruits and vegetables without noting that carrots are better for you than iceberg lettuce. Also, the new Guidelines call for at least half the servings of grains to be in the form of whole grains. Information is included on non-meat sources of iron and on non-dairy sources of calcium and vitamin D. Overall, there are some positive changes to the Dietary Guidelines, although they still strongly promote the use of fish and dairy products. The Dietary Guidelines and related information can be seen at health.gov/dietaryguidelines/dga2005/document/. Printed copies can be purchased from the U.S. Government Printing Office at (866) 512-2011.
- U.S. Depts. of Agriculture and Health and Human Services.
- Dietary Guidelines for Americans. Washington, DC. 2005.
