Scientific Update

Levels of Salicylic Acid, an Active Component of Aspirin, Are Higher in Vegetarians

Regular use of aspirin by adults appears to reduce the risk of heart disease and colon cancer and may also reduce the risk of lung cancer, breast cancer, and Alzheimer's disease. One component of aspirin that appears to have a great effect on health is salicylic acid. Salicylic acid is also found in fruits and vegetables, especially in herbs and spices. Researchers in Scotland hypothesized that vegetarians would have higher levels of salicylic acid in their blood than non-vegetarians because vegetarians typically eat more fruits and vegetables. Blood was sampled from 37 vegetarians and 39 non-vegetarians, none of whom was taking aspirin or other drugs containing salicylic acid. Blood was also sampled from 14 people who took aspirin regularly. There was great variability in blood salicylic acid levels. Higher concentrations were found in the vegetarians compared to the non-vegetarians, with the highest levels seen in those taking aspirin. Some vegetarians had levels as high as the aspirin users. The salicylic acid levels in fruits and vegetables may help to explain why diets that are high in fruits and vegetables are associated with reduced risk of heart disease and colon cancer.

Blacklock CJ, Lawrence JR, Wiles D, et al. 2001. Salicylic acid in the serum of subjects not taking aspirin. Comparison of salicylic acid concentrations in the serum of vegetarians, non-vegetarians, and patients taking low dose aspirin. J Clin Pathol 54:553-555.

VRG Advisors Publish Recommendations for Vegan Infants and Children

Virginia Messina, MPH, RD, and I had two papers published in the Journal of The American Dietetic Association that provide guidelines for dietitians and other health care professionals working with vegan families. The guidelines address nutritional considerations for vegan infants and children. A press release about these articles is headlined, "Vegan Diets Can Meet Children's Nutritional Needs." These articles would be useful to share with health care providers who have questions about vegan diets for infants and children. Much of the information in these articles was covered in VRG's brochure, Vegan Nutrition in Infancy and Childhood, available on VRG's website at <www.vrg.org/nutrition/pregnancy.htm>, or via mail at PO Box 1463, Baltimore, MD 21203 (send a SASE to request a printed copy).

Blood Lead Levels Are Lower in Chinese Adults Eating More Tofu

Lead is a mineral that is toxic to humans. Nutritional factors such as protein, calcium, iron, zinc, and vitamin C can change how much lead is absorbed and excreted. More than 1,100 young Chinese adults had the amount of lead in their blood measured. Those eating the most tofu (more than 25 ounces per week) had blood lead levels that were 11% lower than the levels of lead seen in those eating less than eight ounces of tofu per week. The high calcium content of tofu may interfere with lead absorption and reduce the amount that is retained. It is very important to limit exposure to lead. Dietary adjustments like eating more tofu may provide additional protection.

Chen C, Wang X, Chen D, et al. 2001. Tofu consumption and blood lead levels in young Chinese adults. Am J Epidemiol 153:1206-1212.

Fruits and Vegetables and Heart Disease

There have been two recent reports on fruits and vegetables and heart disease. The first was a large study of more than 80,000 women and 42,000 men that examined fruit and vegetable consumption and heart disease. Dietary intakes were assessed at various points throughout the study. Women were followed for 14 years and men for eight years to see which factors were associated with heart attacks or deaths from heart disease.

The results of this study will be very appealing to vegetarians and others whose diets include generous amounts of fruits and vegetables. Those who had the highest intakes of fruits and vegetables had a markedly lower risk for heart disease compared to those eating the smallest amount of fruits and vegetables. An intake of more than four servings per day seemed to reduce the risk of heart disease, and eight or more servings per day led to an even greater decrease. If the number of fruits and vegetables eaten daily increased by only one serving per day, there was a four percent lower risk of heart disease. A two-serving increase reduced risk eight percent and so on. The fruits and vegetables that appeared to have the greatest effect were green leafy vegetables, vegetables in the cabbage family (broccoli, cabbage, etc.), and vitamin C-rich fruits and vegetables (citrus fruits, strawberries, broccoli). While the results seen are not quite as dramatic as those seen when certain drugs are used (statins), there are so many other benefits of consumption of fruits and vegetables that eating at least eight servings per day of fruits and vegetables sounds like a very prudent move. So, add some berries to your breakfast bowl of cereal, put lots of sliced tomatoes on your sandwich at lunch (or try a veggie sandwich), add finely chopped kale to a pot of soup, and crunch some raw or lightly steamed broccoli for a snack.

The second study was an intervention study in which one group was placed on a diet with more fruits, vegetables, and lowfat dairy products (lower in fat and saturated fat); another group was placed on a diet with more fruits and vegetables; and a third group remained on their usual diets. They followed these diets for eight weeks. The group on the diet with fruits, vegetables, and dairy products saw a reduction in their total, HDL, and LDL cholesterol levels as well as a reduction in blood pressure. Triglyceride levels did not increase. This is significant because usually lowfat, high-carbohydrate diets lead to an unfavorable increase in triglyceride levels. Perhaps this is not as likely to occur when a lower-fat diet is based on plants and whole grains.

Few changes were seen in the groups eating more fruits and vegetables, and the group eating their usual diets, probably because their diets continued to have higher levels of fat and saturated fat. It would have been interesting to see if a diet that was low in fat and saturated fat and high in fruits and vegetables (but not in dairy products) would have had the same effect. The study authors recommend that typical Americans eat twice the average daily servings of fruit, vegetables, and dairy products; one-third the usual amount of beef, pork, and ham; one-half the usual amount of fats and oils; and one-quarter the usual amount of snacks and sweets.

It certainly appears, based on these studies, that eating more fruits and vegetables can have significant health effects.

High Protein Diets

High protein diets are often promoted for weight loss. The concern with this type of diet is that excess dietary protein can compromise kidney function over time in some individuals, and that excess animal protein may increase risk of heart disease. What if the high protein diet is high in vegetable protein? That's the question that Canadian investigators set out to answer. Twenty men and women with high blood cholesterol levels ate diets with either 16% of calories from protein or 27% of calories from protein (a good deal of this was wheat gluten — protein from wheat). The high protein diet led to lower serum triglyceride levels and lower levels of oxidized (harmful) LDL cholesterol. No change was seen in total or HDL cholesterol. Apparently the higher protein diet had no effect on kidney function, although the study period may have been too short to see a change. Diets with generous amounts of vegetable protein may have the same effect (reduced triglyceride levels), as is seen with using more monounsaturated fats and may even offer more benefits since oxidized LDL cholesterol was also lowered. The authors call for additional study of diets high in plant protein (more than 15-20% of calories) before recommending that this type of diet be used.

Jenkins DJA, Kendall CWC, Vidgen E, et al. 2001. High-protein diets in hyperlipidemia: effect of wheat gluten on serum lipids, uric acid, and renal function. Am J Clin Nutr 74:57-63.