SCIENTIFIC UPDATE
By Reed Mangels, PhD, RD, FADA
Adventist Health Study-2 Examines Prostate Cancer Risk in Vegetarians and Near Vegetarians
According to the American Cancer Society, one in seven men in the United States will develop prostate cancer; one in 38 will die from it. A recently published study of Seventh-day Adventists examined risk of prostate cancer in men who choose different diets and who have low rates of cigarette smoking and alcohol use, both of which increase the risk of developing prostate cancer. Approximately 27,000 men were studied for an average of 7.8 years. Over that time period, 1079 developed prostate cancer. Based on their reported diet at the beginning of the study, men were classified as "vegan" (eating any animal product less than once a month), "lacto-ovo vegetarian" (eating meat, poultry, fish less than once a month), "pesco-vegetarian" (eating meat or poultry less than once a month; eating fish at least once a month), "semi-vegetarian" (eating meat or poultry at least once a month but eating meat/fish/poultry less than once a week), and "non-vegetarian." Approximately 8% of the men studied were classified as "vegan." Compared to "non-vegetarians," "vegans" had a 35% lower risk of developing prostate cancer. White "vegans" had a significantly lower risk of prostate cancer; black "vegans" also had lower risk but it was not statistically significant. Other types of vegetarian or near-vegetarian diets were not associated with a reduced risk of prostate cancer.
Tantamango-Bartley Y, Knutsen SF, Knutsen R, et al. 2015. Are strict vegetarians protected against prostate cancer? Am J Clin Nutr. [Epub ahead of print].
Eat More Fruits & Vegetables
We've all heard that fruits and vegetables are good for us. People who eat more fruits and vegetables have a lower risk of heart disease. Will eating more fruits and vegetables also help with weight control? That's what researchers from Harvard University set out to investigate. They studied more than 130,000 men and women in the United States. They looked at dietary and weight changes over several periods of 4 years each, investigating whether making a change in fruit and vegetable intake was associated with a change in weight. An increase of one serving per day of vegetables was associated with a 0.25 pound weight loss over a 4 year period; an increase of one serving per day of fruit was associated with a 0.53 pound weight loss over the same time period. This doesn't sound like much until you realize that the average person gained 2-5 pounds over a 4-year period. An increase in servings of berries, apples, pears, tofu/soy, cruciferous vegetables, and green leafy vegetables was associated with the greatest weight loss. An increased intake of corn, potatoes, and other starchy vegetables was associated with weight gain. Based on their results, the researchers recommend that people increase their intake of fruit by one or two more servings per day and their intake of vegetables by one or two more servings per day to reduce the risk of gaining weight as they grow older.
Bertoia ML, Mukamal KJ, Cahill LE, et al. 2015 Sep 22. Changes in intake of fruits and vegetables and weight change in United States men and women followed for up to 24 years: analysis from three prospective cohort studies. PLoS Med. 12(9):e1001878.
Vegetarian Diets are an Effective Treatment for High Cholesterol
Elevated concentrations of lipids (cholesterol, triglycerides, and LDL-cholesterol) in our blood are associated with an increased risk of heart disease and of dying from heart attacks and strokes. Even a relatively small reduction in these concentrations can reduce the risk of bad things happening; that's why so many people are on statins and other medications that lower blood lipids. Dietary and lifestyle changes are often overlooked but offer an effective way to prevent and treat heart disease, without the side effects that can occur with medications. Vegetarians tend to have lower blood cholesterol concentrations than do non-vegetarians, and so it is only logical that researchers would investigate whether blood lipids would be affected if they placed people on vegetarian diets. This has been done in at least 11 studies, 7 of which used a vegan diet. Results from these studies were combined using a technique called meta-analysis. Studies used people with normal and with elevated cholesterol. The average decrease in blood cholesterol concentration when a person moved from a non-vegetarian to a vegetarian or vegan diet was 14 mg/dL; LDL concentration decreased 13 mg/dL. These kinds of decreases correspond to an estimated 9 to 10.6% decrease in risk of heart disease. In addition, subjects lost weight on the vegetarian diets — another way to reduce risk of heart disease. This study's results suggest that vegetarian diets should be recommended to reduce total or LDL cholesterol.
Wang F, Zheng J, Yang B, Jiang J, Fu Y, Li D. 2015.Effects of vegetarian diets on blood lipids: A systematic review and meta-analysis of randomized controlled trials. J Am Heart Assoc. [Epub ahead of print].
Vegetarian and Vegan Diets are Popular with Ultra-marathon Runners
A marathon is a 26.2-mile race; an ultramarathon is any race that is longer than a marathon. Ultramarathoners like Scott Jurek have popularized the use of vegan diets. Researchers at the University of South Carolina and the University of Minnesota investigated dietary practices of ultramarathoners, marathoners, and half marathoners to see how commonly vegan and vegetarian diets were used. Study participants, all of whom had completed an ultramarathon, a marathon, or a half marathon in the past year, responded to an online survey. They were asked to select a category that best described their current diet. Categories included "vegan," "vegetarian," "pesco-vegetarian," and "semi-vegetarian." They were also asked to respond to questions that allowed the researchers to assess how healthy the subjects' diets were. The majority of subjects reported that they followed either a "generally healthy diet" or no particular diet; 8% said they were "vegetarian"; 5% were "vegan." Ultramarathoners were almost twice as likely to report that they followed a "vegetarian" or "vegan" diet as marathoners and half marathoners combined. Runners identifying as vegan or vegetarian had higher scores for dietary quality than runners following other diets. The somewhat higher percentage of vegetarians and vegans in this study compared to VRG polls may be because this study allowed subjects to categorize their diets whereas VRG polls ask subjects which foods they never eat. Additionally, vegetarian and vegan diets may be more common among this population of highly active individuals than among the general population.
Turner-McGrievy GM, Moore WJ, Barr-Anderson D. 2015. The Interconnectedness of diet choice and distance running: results of the Research Understanding the NutritioN of Endurance Runners (RUNNER) Study. Int J Sport Nutr Exerc Metab. [Epub ahead of print].
Bean Loaf, Anyone?
If you want to stave off hunger pangs, protein is your friend. Among the nutrients, protein is the one that is most satiating. Fiber can also help with making people feel full for a longer period. What if you could combine the benefits of fiber and protein? That's what researchers did when they identified beans as a good source of protein and fiber. They created recipes using beans or beef to make meatloaf-like dishes and served them to 28 subjects. Half the subjects got the bean loaf and half got the beef loaf. A week later they came back and got the loaf that they didn't get the week before. The subjects had their loaf at lunch and were to rate their hunger over the next 3 hours. They were offered a variety of snacks 3.5 hours after their lunch and the amount of snacks eaten was recorded. There was no difference in hunger for up to 3 hours after lunch between the subjects who got the bean loaf and those who got the beef loaf. There was also no difference in the amount of snacks that were eaten. The bean loaf was higher in fiber but lower in protein than the beef loaf. These results suggest that even though beans may be somewhat lower in protein than beef (on a per-serving basis), the high fiber content of the beans helps to make them as filling as beef. Beans offer other benefits because they are low in fat and saturated fat. This study shows that if you eat a serving of beans, you probably won't have to worry about feeling hungry a few hours later.
Bonnema AL, Altschwager D, Thomas W, Slavin JL. 2015. The effects of a beef-based meal compared to a calorie matched bean-based meal on appetite and food intake. J Food Sci. 80:H2088-93.
