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Prevalence and Risk of Type 2 Diabetes Lowest Among Vegans

Loma Linda University scientists studied the relationship between various diet types (vegans, lacto-ovo vegetarians, pescatarians, and nonvegetarians) and prevalence of type 2 diabetes in a large cohort of Seventh-Day Adventists in North America. They found that vegans had the lowest prevalence (2.9%) of the disease, while nonvegetarians had the highest (7.6%). Additionally, the vegan diet was associated with a nearly one-half reduction in risk of type 2 diabetes compared with the risk associated with nonvegetarian diets.
Diabetes Care. 2009 May 1;32(5):791-796. (Tonstad et al.)

Health Effects of Vegan Diets

A nationwide poll conducted in 2006 determined that 1.4% of the American population is vegan—they eat no meat, fish, dairy, or eggs.  Scientists at Andrews University in Michigan reviewed existing studies about veganism to assess the pros and cons of adopting such a diet.  Overall, vegans tend to have lower BMI, lower serum cholesterol, and lower blood pressure, decreasing their risk of developing cardiovascular disease.  However, because of the elimination of all animal products, vegans are at greater risk of certain nutritional deficiencies such as vitamins B12 and D, calcium, and omega-3 fatty acids.  It is suggested that vegans consume foods that are fortified with these nutrients or that they take appropriate supplements to prevent deficiencies.
American Journal of Clinical Nutrition.  May 2009; 89:1627s-33s [Craig WJ]

Low-Fat Vegan Diet May Be Most Effective in Controlling Type 2 Diabetes

Researchers from the George Washington University conducted a randomized, controlled trial on 99 participants with type 2 diabetes. 49 participants were randomly selected to follow a low-fat vegan diet, while the remaining 50 were to adopt a diet following the 2003 American Diabetes Association guidelines (“conventional diet”). The groups followed their assigned diets for 74 weeks. By the end of the trial, the researchers found that both diets had resulted in weight loss, improved glycemic control as measured by HbA1C, and a reduction in blood triglycerides. Once the results were controlled for medication adjustments, however, the low-fat vegan diet appeared to improve glycemic control and blood triglycerides more than the conventional diet. This study illustrates the physiological benefits of adopting a plant-based diet.
American Journal of Clinical Nutrition. 2009 May 1;89(suppl):1588S-96S. (Barnard et al.)

Nutrition Concerns for Vegetarian Athletes

Researchers from the University of Rome conducted a review of the recent literature surrounding the nutritional adequacy of vegetarian diets among athletes.  Although it remains unclear whether vegetarian diets are preferable to omnivorous diets for athletic performance, the data show that it is possible for vegetarian athletes to maintain good nutritional profiles. However, vegetarian athletes may have to be more vigilant about ensuring adequate calorie, Iron, Zinc, Vitamin D, and Vitamins B12 (cyanocobalamin) and B2 (riboflavin) intake, through supplementation if necessary. Additionally, creatine supplementation may benefit vegetarian athletes who engage in repeated bouts of short-term high-intensity exercise.
Sport- Und Präventivmedizin. 2009 Jan;39(1):20-24. (Borrione et al.)

Vegetarians May Have Increased Risk of Bone Fracture

Researchers at Loma Linda University investigated a cohort of peri- and post-menopausal women over a period of 25 years to compare incidences of wrist fracture with diet type. They found that vegetarians who consumed low amounts of protein suffered the most wrist fractures. However, increasing levels of plant-based protein foods decreased risk by 68% and increasing meat intake decreased risk by 80%. These findings suggest that dietary protein plays a significant role in bone health among middle-aged and elderly females.
Public Health Nutrition. 2008 June 1;11(6):564-572. (Thorpe et al.)

Low Omega-3 Fatty Acid Status in Vegans

Researchers at the University of Vienna compared the ratio of omega-6:omega-3 polyunsaturated fatty acids (PUFAs) in omnivores, vegetarians, vegans, and semi-omnivores to assess essential fatty acid status as it relates to diet. They found that vegans had the highest average ratio of omega-6:omega3 PUFAs. High ratios are believed to be pro-inflammatory and may also contribute to tissue decline and neurological dysfunction. While the authors emphasize the need for further research on this topic, they also urge vegetarians and especially vegans to increase their intakes of omega-3 fatty acids from non-animal sources such as algae.
Annals of Nutrition & Metabolism. 2008 Apr;52:37-47. (Kornsteiner et al.)

Vegetarian Diet Does Not Affect Growth & Development in Children

Data from the European Prospective Investigation into Cancer and Nutrition (the EPIC-Oxford study) shows no difference between age at first menstruation or adult height  (measures of growth and development) between lifelong lacto-ovo vegetarian and non-vegetarian women. While the researchers point out that adult vegetarians generally have a lower average BMI, growth and development does not seem to be affected.
Public Health Nutrition. 2005 Aug 1;8(7), DOI 10.1079/PHN2005730. (Rosell et al.)

Blood Pressure and Vegetarian Diets

Lifestyle factors, particularly diet, play a major role in blood pressure regulation.  Randomized, controlled studies indicate that plant-based diets are associated with BP reductions in both normal and hypertensive individuals.  According to this literature review by the Physicians’ Committee for Responsible Medicine, observational studies show that BP levels tend to be lower in individuals following self-selected vegetarian diets.  These findings strongly suggest that individuals with high blood pressure or at risk for developing high blood pressure may benefit from following plant-based vegetarian diets.  
Nutrition Reviews.  January 2005; 63(1):1-8. [Berkow S et al.]

Vegetarian Diets and Pregnancy

Inadequate vitamin B12 during pregnancy is associated with birth defects including neural tube defects and it is known that vegetarians are at risk for developing a B12 deficiency because they do not consume animal products, which are the principle source of this nutrient.  Scientists in Germany compared 70 pregnant women who had been vegetarian or near-vegetarian for at least three years (including 27 lacto-ovo vegetarians and 43 “low meat eaters”) to a control group of 39 pregnant women eating an average Western diet. By testing the women’s blood three times during pregnancy, they concluded that serum B-12 levels of the lacto-ovo vegetarians were lowest, the low meat eaters in the middle and the control group highest. The authors urge that recommended dietary intake levels of B-12 for pregnant women be re-evaluated.
The Journal of Nutrition. December 2004; 134(12):3319-3326. [Koebnick et al.]

Nutrition for Vegetarian Athletes

Scientists at the University of British Columbia  reviewed possible mechanisms by which vegetarian dietary practices could theoretically influence athletic performance.  After considering many different factors, including protein levels, carbohydrates, iron, vitamin B-12, and creatine levels, the researchers concluded that “well-planned, appropriately supplemented vegetarian diets appear to effectively support athletic performance.” 
Nutrition.  July-August 2004; 20:696-703.  [Barr and Rideout]

Type 2 Diabetes and the Vegetarian Diet

While there are currently few data specifically connecting vegetarian diets and diabetes prevention or treatment, it is known that many of the specific foods that make up a vegetarian diet have advantages in the treatment of type 2 diabetes.  These foods include whole grains, legumes, nuts, seeds, soy proteins, and plant sterols.  This summary article from researchers at the University of Toronto details the benefits of different plant foods, and concludes that evidence documented in both cohort studies and intervention studies show that vegetarian diets “can help reduce the risk of developing type 2 diabetes and cardiovascular disease—a major complication of type 2 diabetes.”
American Journal of Clinical Nutrition. September 2003; 78(suppl):610S–6S. [Jenkins D et al.]

Vegans have lower prevalence of hypertension

Researchers from Oxford University studied a large cohort of British men and women in the context of diet, lifestyle, and disease risk. They found that hypertension (both systolic and diastolic) is significantly less prevalent among vegan men and women (5.8% and 7.7%, respectively) as compared to omnivorous men and women (15.0% and 12.1%, respectively). The researchers suspect that this is related to the vegan participants’ lower average Body Mass Index.
Public Health Nutrition. 2002 Oct 1;5(5):DOI 10.1079/PHN2002332. (Appleby et al.)