SCIENTIFIC UPDATE
By Reed Mangels, PhD, RD, FADA
Risk of Colorectal Cancer is Lower in Those Avoiding or Limiting Meat Consumption
Each year in the U.S., more people die from cancer of the colon and rectum (colorectal cancer) than from any other cancer except lung cancer. Improved screening and treatment have reduced the death rate from colorectal cancer, though it is still the third most common cancer in men and women, so finding ways to reduce the risk of developing it is important. Studies frequently report a link between red and processed meat consumption and risk of colorectal cancer. Vegetarians, because of their avoidance of all meat, would appear to have a low risk of colorectal cancer; however, British vegetarians did not show a lower risk in a study from about six years ago. Recently, the occurrence of colorectal cancer in more than 77,000 Seventh-day Adventists in the U.S. and Canada was examined. Subjects were classified based on their degree of avoidance of animal products. For example, in this study, "nonvegetarians" eat meat or fish at least weekly, "lacto-ovo vegetarians" eat dairy products and eggs but eat meat or fish less than once a month, and "vegans" eat animal products less than once a month. Study subjects were asked about their diet and were then studied for an average of 7 years. Health records were examined to see which subjects developed cancer during the follow-up period. Overall, subjects classified as "vegetarian" (includes everything from vegans who never eat animal products to "semi-vegetarians" who eat meat or fish less than once a week) had about a 20% lower risk of developing colorectal cancer than nonvegetarians. These results are especially striking because the nonvegetarians ate relatively little meat compared to U.S. averages and ate very little processed meat. Had the "vegetarian" group been compared to a group eating a more typical U.S. diet, we'd expect to see an even greater reduction in risk of developing colorectal cancer.
Orlich MJ, Singh PN, Sabaté J, et al. 2015. Vegetarian dietary patterns and the risk of colorectal cancers. JAMA Intern Med.175:767-76.
Why Don't More People Know About the Benefits of Plant-Based Diets for People with Type 2 Diabetes?
As we've reported before, vegan diets have been effectively used to treat type 2 diabetes, the most common kind of diabetes. Based on studies like this one, in 2013, the Canadian Diabetes Association recommended that plant-based diets be used in the treatment of type 2 diabetes. Despite studies showing that plant-based diets are an effective treatment for type 2 diabetes and despite the recommendations of the Canadian Diabetes Association, few practitioners seem to be recommending plant-based diets for their clients with type 2 diabetes. Canadian researchers investigated clients' and providers' ideas about plant-based diets. They surveyed close to 100 people with diabetes and 25 providers, mainly registered dietitians and nurses. Although almost 90% of the people with diabetes had never before heard of using a plant-based diet as a part of treatment, two-thirds said that they would be willing to try this kind of diet. They wanted individual and group classes on vegetarian cooking. Their main concerns were a lack of family support, lack of knowledge of meal preparation and planning, and a liking for meat. Although more than 70% of providers were aware that plant-based diets could be used to manage type 2 diabetes, less than one-third are recommending plant-based diets. Practitioners expressed concerns that a plant-based diet was too hard to follow and that it would not be acceptable to their clients. These results suggest that some practitioners are not aware of their clients' interest in plant-based diets. More consistent promotion of plant-based diets along with vegetarian cooking classes could lead to better management of type 2 diabetes. Although this study was conducted in Canada, it is likely that similar results would be seen in the United States.
Lee V, McKay T, Ardern CI. 2015 Jan 31. Awareness and perception of plant-based diets for the treatment and management of type 2 diabetes in a community education clinic: a pilot study. J Nutr Metab. Epub.
Vegans and Lacto-ovo Vegetarians Shown to Have Healthy Bones
Nutrition and exercise play crucial roles in bone health. The list of nutrients needed for strong bones is long and includes calcium, vitamin D, protein, vitamin K, folate, magnesium, potassium, and vitamin B12. Vegetarian diets tend to have generous amounts of some of these nutrients but may be lower in others. How does a vegetarian diet affect bone health? That's the question that researchers set out to examine in a study of 82 healthy 19-50 year olds. All subjects had followed their current diet for at least a year. There were 27 nonvegetarians, 27 lacto-ovo vegetarians (never ate meat, poultry, fish; ate at least 3 servings of eggs and/or dairy per week) and 28 vegans (never ate meat, poultry, fish, dairy, eggs). All subjects were normal weight and had similar levels of activity. There was no significant difference in bone mineral density (a measure of bone health) between the groups and it was in a normal range. Average protein intake was lower in the vegetarians; magnesium, folate and vitamin K intakes were highest in the vegans. Those vegans who had the lowest protein intakes also tended to have the lowest bone mineral densities. This suggests that getting adequate protein is important for bone health. The results of this study support the idea that following a nutritious vegan (or lacto-ovo) diet supports bone health.
Knurick JR, Johnston CS, Wherry SJ, Aguayo I. 2015.Comparison of correlates of bone mineral density in individuals adhering to lacto-ovo, vegan, or omnivore diets: a cross-sectional investigation. Nutrients. 7:3416-26.
Mistaken Beliefs Regarding Sugary Drinks
Sugary drinks, including regular soda, sports drinks, sweetened tea, and fruit drinks, are the main source of added sugar in U.S. diets. These drinks are associated with an increased risk of obesity, with one study finding that every 8 ounces of sugary drink consumed per day increases a child's risk of obesity by 60%. Fruit drinks are different from 100% fruit juice because of the amount of sugar added to fruit drinks (no sugar is added to 100% fruit juice). On average, fruit drinks have almost as much added sugar as the same amount of a sweetened soft drink. These drinks also may contain less than 10% fruit juice. Researchers surveyed close to 1,000 parents about their beliefs about sugary drinks. Almost half of parents rated flavored water as healthy and a quarter considered fruit drinks and sports drinks to be healthy. Four of five parents of children younger than 12 years old gave their children fruit drinks, possibly thinking these products were healthier than soda (they're not). Advertising undoubtedly plays a role in parents' beliefs as does product labeling. Fruit drinks and sports drinks are promoted as being good sources of vitamins, minerals, and electrolytes. Water and limited amounts of 100% fruit juice are better choices.
Munsell CR, Harris JL, Sarda V, Schwartz MB. 2015. Parents' beliefs about the healthfulness of sugary drink options: opportunities to address misperceptions. Public Health Nutr. [Epub ahead of print].
Teen Dietary Choices May Influence Breast Cancer Risk
Breast cancer, which affects 1 in 8 women in the U.S., may have its beginnings during adolescence. This is the time when the number of cells is increasing rapidly and when breast tissue may be especially vulnerable to substances that can cause cancer in later life. Many studies of diet and breast cancer have looked at women's diets during midlife and not during adolescence. A recent study asked women about the amount of red meat that they ate when they were adolescents. The study had more than 40,000 female subjects age 33-52 years at the start of the study. They were asked to remember the foods they ate when they were in high school. The researchers observed the women for a 13-year period to see who would be diagnosed with breast cancer. The women who reported eating the most red meat as adolescents had a significantly higher risk of developing breast cancer before menopause compared to women who ate the least red meat. These results, which are similar to those of other studies, suggest that limiting red meat during adolescence may play a role in reducing the risk of breast cancer.
Farvid MS, Cho E, Chen WY, Eliassen AH, Willett WC. 2015. Adolescent meat intake and breast cancer risk. Int J Cancer. 136:1909-20.
