Scientific Update

A Review of Recent Scientific Papers Related to Vegetarianism

By Reed Mangels, PhD, RD, FADA

Vitamin B12 in the News

A recent report from the Centers for Disease Control and Prevention (CDC) on vitamin B12 deficiency in two children in Georgia received wide media attention. The children, who were 15 months and 30 months old at the time of their diagnoses, had been breast-fed by mothers who followed vegan or near-vegan diets.

Information on the use of vitamin B12 supplements by the mothers and the children was incomplete. If vitamin B12 supplements were used at all, they were only used sporadically. Both mothers and their children did not have adequate amounts of vitamin B12. Both children were growing poorly, both were developmentally delayed, and one child had seizures, apparently related to the vitamin B12 deficiency.

While it is unfortunate that some media reports suggested that a vegan diet (rather than a lack of vitamin B12) caused these conditions, this report does serve as a reminder of vitamin B12’s importance. All vegans, especially pregnant and lactating women, infants, and children, need a regular source of vitamin B12. Reliable sources include foods fortified with vitamin B12, such as some breakfast cereals, meat analogs, soy or rice milk, and nutritional yeast (Vegetarian Support Formula). Vegan infants and young children can also obtain vitamin B12 through breast milk from mothers with adequate nutritional status or from infant formula. If it is not possible to meet recommendations for vitamin B12 through food, a daily supplement should be taken that contains at least the RDA for vitamin B12.

Anon. 2003.
Neurologic impairment in children associated with maternal dietary deficiency of cobalamin—Georgia, 2001.MMWR Morb Mortal Wkly Rep 52:61-4.

Vitamin D Appears Important in Reducing Hip Fracture Risk

Researchers continue to look for factors that can prevent osteoporosis and reduce the risk of hip fracture. A study from Harvard University examined the dietary intakes of more than 70,000 postmenopausal women over an 18-year period and looked to see which women had hip fractures. The women’s calcium intake did not seem to be associated with their risk of fracturing a hip, even when they used as much as 1500 milli-grams of calcium daily. Women who drank the most cow’s milk had about the same risk of hip fracture as women who drank the least cow’s milk. Did anything reduce the risk of hip fracture? Vitamin D did. Women who had higher levels of vitamin D from their diet and from supplements had a lower risk of hip fracture than did women who consumed less vitamin D. Sources of vitamin D for vegans include foods fortified with vitamin D, like some brands of soymilk, rice milk, and breakfast cereals. Vitamin D supplements can also be used to meet these needs.

Feskanich D, Willett WC, Colditz GA. 2003.
Calcium, vitamin D, milk consumption, and hip fractures: a prospective study among postmenopausal women. Am J Clin Nutr 77:504-11.

Dietary Adjustments Slow Progression of Heart Disease in Vegetarians or Near-Vegetarians

What if someone is following a vegetarian diet and develops heart disease? Is the fact that the person is vegetarian enough, or are there dietary changes that would help to slow the progression of the heart disease? These are some of the questions a recent study from India set out to answer. Close to 1,000 people with major risk factors for heart disease (like high blood pressure, high blood cholesterol, or diabetes) or who had had a heart attack earlier were studied. Two-thirds of the subjects were lacto-vegetarians.

Unfortunately, we do not have information on the amount of fat, saturated fat, or cholesterol in their diets before this study. All of the subjects were encouraged to follow a standard cholesterol-lowering diet (less than 30 percent of calories from fat, less than 10 percent of calories from saturated fat, less than 300 milli-grams of cholesterol), to exercise, to avoid smoking and alcohol, and to practice relaxation. In addition, half of the subjects, the intervention group, were encouraged to eat more fruits, vegetables, nuts, and whole grains, as well as to use oils high in omega-3 fatty acids. After two years, the intervention group weighed less and had lower blood pressure, lower blood cholesterol and LDL cholesterol, and lower blood sugar levels than the group following the standard diet. The intervention group also had fewer heart attacks and fewer deaths from heart disease. This study suggests that dietary changes, including eating a diet high in fruits, vegetables, nuts, whole grains, and oils high in omega-3 fatty acids, can slow the progression of heart disease in vegetarians.

Singh RB, Dubnov G, Niaz MA, et al. 2002.
Effect of an Indo-Mediterranean diet on progression of coronary artery disease in high risk patients (Indo-Mediterranean Diet Heart Study): a randomized single-blind trial. Lancet 360:1455-61.

Vegan Diet and Breast Cancer Risk

Insulin-like growth factor I, or IGF-I for short, is a hormone that appears to promote the growth of both normal and malignant cells in the breast. Elevated levels of IGF-I in the blood have been associated with an increased risk of developing breast cancer before menopause. Close to 300 British women were studied, 92 of whom were vegan, and 101 vegetarian (used dairy and/or eggs). The average level of IGF-I was lower in vegan women than in the other groups. The researchers believe that the vegans’ lower intake of animal protein or of essential amino acids may explain their lower levels of IGF-I.

Allen NE, Appleby PN, Davey GK, et al. 2002.
The association of diet with serum insulin-like growth factor I and its main binding protein in 292 women meat-eaters, vegetarians, and vegans. Cancer Epidemiol Biomarkers Prev. 11:1441-8.

Protein Recommendations for Vegetarians

A recent report used data combined from 19 studies to establish new recommendations for protein intake for adults. One question that was asked was whether people on “vegetable” diets (>90 percent of protein from non-animal sources) would have higher protein needs than those whose dietary protein was mainly from animals or from a mix of animals and plants. The source of dietary protein was seen to have little effect on protein requirements. The authors encourage people following plant-based diets to use a variety of protein sources, including legumes, nuts, seeds, and grains, to ensure that needs for essential amino acids are met. They recommend that healthy adults, whether vegetarian or not, get 0.83 grams of protein per kilogram of body weight (or 0.38 grams of protein per pound) daily.

Rand WM, Pellett PL, Young VR. 2003.
Meta-analysis of nitrogen balance studies for estimating protein requirements in healthy adults. Am J Clin Nutr 77:109-27.

Vegetarianism and Male Fertility in the Presence of Environmental Pollutants

Various chemicals, such as pesticides, PCBs, and phthalate esters (PEs), and other pollutants are believed to have a harmful effect on men’s fertility. A study in India examined environmental factors that could lead to infertility. Twenty-one men who were infertile for no apparent reason were compared with 32 men with normal fertility. PCBs and PEs were found in the semen of the infertile men but not in the semen of the fertile men. These results suggest that contaminants present in the environment may lead to a deterioration of sperm count, motility (ability to move), and fertilizing ability.

Among infertile men, levels of PCBs and PEs were highest in urban fish eaters and lowest in rural vegetarians. Rural fish eaters and urban vegetarians had intermediate levels. The higher levels of these substances found in fish eaters are probably due to eating fatty fish contaminated with PCBs and PEs. Urban residents are exposed to PCBs and PEs in the environment due to industrial wastes. Even rural vegetarians can eat plant foods that have been contaminated with PCBs and PEs from the polluted soil or irrigation water. While a vegetarian diet cannot prevent exposure to pollutants in the environment, vegetarians in this study appeared to have lower levels of these harmful substances.

Rozati R, Reddy PP, Redanna P, Mujitaba R. 2002.
Role of environmental estrogens in the deterioration of male factor fertility. Fertil Steril 78:1187-94.