SCIENTIFIC UPDATE
A REVIEW OF RECENT SCIENTIFIC PAPERS RELATED TO VEGETARIANISM
By Reed Mangels, PhD, RD, FADA
Make That WHOLE Wheat
The average American eats less than one serving of whole grains a day. Sad, isn't it? Current recommendations call for eating three or more servings of whole grains every day, something many vegetarians already do. What's so important about whole grains? Well, for starters, they seem to protect against various types of cancer, heart disease, and type 2 diabetes. When grains are refined, they lose fiber, magnesium, vitamin E, and other nutrients that play a role in health. A recent study1 suggests that middle-aged people can reduce their risk of heart and blood vessel disease by eating more whole grains. This study looked at the thickness of the walls of the carotid arteries, which are tubes that carry blood to the brain, of close to 1,200 adults and measured changes in thickness over a five-year period. Thicker walls increase the risk of cardiovascular disease. Subjects eating the most whole grains had less thickening of the walls of their carotid arteries over time, suggesting that they were at lower risk for developing cardiovascular disease. Another study found that women who had higher intakes of whole grains had a lower risk of hypertension. 2 So, for lots of reasons, choose whole wheat bread and whole grain cereals and pasta.
- 1 Mellen PB, Liese AD, Tooze JA, et al. 2007. Wholegrain intake and carotid artery atherosclerosis in a multiethnic cohort: the Insulin Resistance Atherosclerosis Study. Am J Clin Nutr 85:1,495-1,502.
- 2 Wang L, Gaziano JM, Liu S, et al. 2007. Whole- and refined-grain intakes and the risk of hypertension in women. Am J Clin Nutr 86:472-79.
Vegetarian DHA — Not a Fish Story
DHA is an omega-3 fatty acid found mainly in oily fish. It appears to play a role in reducing the risk of heart disease and may be involved in preventing other chronic diseases. Vegetarian diets typically contain little DHA and vegan diets contain almost none unless fortified foods or supplements are used. Some people opt to use DHA supplements. DHA supplements for vegans and vegetarians are derived from microalgae. Recently, some manufacturers have begun adding DHA derived from microalgae to foods. A key question is whether this microalgae-derived DHA can be absorbed and used by our bodies. A recent study examined this question, using two different kinds of microalgae-derived DHA supplements and a snack bar enriched with microalgaederived DHA. Subjects took the supplements or ate the snack bars for a month. All of the products led to higher levels of DHA in the subjects' blood, suggesting that the vegetarian DHA was well absorbed and used.
- Arterburn LM, Oken HA, Hoffman JP, et al. 2007. Bioequivalence of docosahexaenoic acid from different algal oils in capsules and in a DHAfortified food. Lipids Aug 23 [Epub ahead of print].
High Folate Intake Reduces Breast Cancer Risk
Folate is a vitamin that is found in many foods, including orange juice, dried beans, and vegetables. Vegetarians get at least as much folate and often more folate than do non-vegetarians. Swedish researchers examined folate's role in breast cancer. Close to 12,000 Swedish women aged 50 and older were studied for 9 1/2 years. During that time, 392 women developed breast cancer. Women who had the highest dietary intake of folate had a lower risk of developing breast cancer compared to women with the lowest folate intake. This study suggests that increased folate intake can reduce the risk of postmenopausal breast cancer. These results may help to explain why women whose diets are high in meat and presumably low in vegetables and dried beans have higher rates of breast cancer. Vegetarian diets featuring plenty of vegetables and dried beans provide generous amounts of folate.
- Ericson U, Sonestedt E, Gullberg B, et al. 2007.
- High folate intake is associated with lower breast cancer incidence in postmenopausal women in the Malmo Diet and Cancer cohort. Am J Clin Nutr 86:434-43.
Adequate Protein is Key to Preventing Wrist Fractures
Almost one out of six women will fracture a wrist in their adult life. This doesn't sound like a big deal, but it can raise concerns about overall bone strength. People who have fractured a wrist are more likely to have a fractured hip at some point. Researchers at Loma Linda University wondered if diet played a role in wrist fractures. They started with 1,865 women and tracked them for 25 years. Approximately 40 percent of the women were vegetarian. As the women got older, they were more likely to have had a broken wrist. Women who were physically active were less likely to fracture a wrist, maybe because weight-bearing exercise can improve bone strength. Among the vegetarians, those eating the most plant-based protein foods (beans, nuts, meat analogues) had the lowest risk of wrist fracture. Vegetarians who ate very few vegetablebased protein foods (fewer than three servings per week) had the highest risk of wrist fracture. According to one of the researchers, calcium intake was not significantly different between groups eating different amounts of protein. Adequate protein is important for strong bones. This study suggests that it is important for vegetarians to eat a diet that provides adequate and varied protein sources to promote healthy bones.
- Thorpe DL, Knutsen SF, Beeson WL, et al. 2007.
- Effects of meat consumption and vegetarian diet on risk of wrist fracture over 25 years in a cohort of peri-and postmenopausal women. Public Health Nutr Aug 9:1-9 [Epub ahead of print].
Vitamin D in Children and Teens in the United States
Vitamin D promotes the absorption of calcium and enhances bone formation. People who don't get enough vitamin D, either from their diet or from sun exposure, have an increased risk of bone fractures. Vitamin D is stored in our bodies for times when we're not able to make vitamin D. The best way to measure how much vitamin D a person has stored is to measure the amount of a substance called calcidiol in his or her blood.
Researchers investigated levels of calcidiol in approximately 400 children and adolescents age 6 to 21 years in the Philadelphia area. More than half of the children and teens had low levels of vitamin D. Low levels were more likely to be seen in the winter months, in older children, in those with low dietary vitamin D, and in black children. These results underscore the importance of adequate dietary vitamin D, especially during the winter when sun exposure is limited. People with darker skin seem to require longer sun exposure to produce vitamin D and should also pay attention to getting enough vitamin D from their diets. Vegan sources of vitamin D include vitamin D-fortified soymilks and rice milks and vitamin D supplements.
- Weng FL, Shults J, Leonard MB, et al. 2007.
- Risk
factors for low serum 25-hydroxyvitamin D concentrations
in otherwise healthy children and
adolescents. Am J Clin Nutr 86:150-58.
Does Diet Play a Role in Lung Disease?
Chronic obstructive pulmonary disease (COPD for short) is the name for a number of lung diseases that can cause shortness of breath, wheezing, and swelling of the airways. The most common forms of COPD are chronic bronchitis and emphysema. Cigarette smoking is the main cause of COPD, but not every smoker develops COPD, which suggests that other factors may also play a role. A study of more than 70,000 women examined diet's role in COPD. The women were asked about their smoking history, their diet, and whether they had developed COPD during the 16-year study period. Based on the women's descriptions of their diet, two major dietary patterns were identified. One was characterized by generous amounts of fruits, vegetables, whole grains, and other foods, including fish, poultry, and lowfat dairy products. The other pattern included a high use of refined grains, red meats, sweets, and high-fat dairy products. Women who developed COPD tended to have a dietary pattern that was more typical of the Standard American Diet—lots of red meat, refined grains, sweets, and fried foods. The more plant-based pattern was associated with a reduced risk of developing COPD. While we can't conclusively say that a vegetarian diet can reduce risk of COPD, it seems likely that a vegetarian diet that includes generous amounts of fruits, vegetables, and whole grains would be beneficial. Of course, stopping smoking (or never starting) is the most important step one can take to reduce the risk of developing COPD.
- Varraso R, Fung TT, Barr RG, et al. 2007.
- Prospective study of dietary patterns and chronic obstructive pulmonary disease among U.S. women. Am J Clin Nutr 86:488-95.
