Clinical Research: Physicians Committee Publications
Clinical Research: Physicians Committee Publications
The Physicians Committee designs and conducts clinical research studies on nutrition and health. Dietary interventions have appeared promising in investigations carried out by numerous research teams, including our own. We have conducted studies that examine the effects of diet on weight, cardiovascular risk, cancer prevention and survival, and other health issues. The Physicians Committee's research aims to develop and test practical interventions that can be used by doctors and patients. The Physicians Committee also conducts detailed reviews of the scientific literature, including meta-analyses.
Neuropathy is a complication of diabetes manifesting as pain, numbness, and other nerve symptoms. The pilot study put 17 adults on a low-fat vegan diet for 20 weeks, with weekly nutrition classes. The researchers found significant improvements in pain, measured by the Short Form McGill Pain questionnaire, the Michigan Neuropathy Screening Instrument physical assessment, and through electrochemical skin conductance in the foot. The participants also lost an average of 14 pounds.
- Bunner AE, Wells CL, Gonzales J, Agarwal U, Bayat E, Barnard ND. A dietary intervention for chronic diabetic neuropathy pain: a randomized controlled pilot study. Nutrition & Diabetes. 2015;5:e158.
Researchers assessed insulin resistance after a meal for 75 overweight participants without diabetes for 16 weeks, half of whom followed a low-fat, vegan diet. Those who consumed the vegan diet increased meal-stimulated insulin secretion and beta-cell glucose sensitivity and lowered their body weight, compared with the control group. Lower body fat increases beta-cells’ ability to regulate blood sugar. These results show that a vegan dietary intervention helps prevent diabetes.
Kahleova H, Tura A, Hill M, Holubkov R, Barnard ND. A plant-based dietary intervention improves beta-cell function and insulin resistance in overweight adults. A 16-week randomized clinical trial. Nutrients. 2018;10. pii: E189. Available at:
This study was funded by the National Institutes of Health. Individuals with type 2 diabetes (n=99) were randomly assigned to a low-fat plant-based diet (n=49) or a diet following the American Diabetes Association (ADA) guidelines (n=50). Participants were evaluated at baseline and 22 weeks. Both a low-fat plant-based diet and a diet based on ADA guidelines improved glycemic and lipid control in type 2 diabetic patients. These improvements were greater with a low-fat plant-based diet.
- Barnard ND, Cohen J, Jenkins DJ, et al. A low-fat vegan diet improves glycemic control and cardiovascular risk factors in a randomized clinical trial in individuals with type 2 diabetes. Diabetes Care. 2006;29:1777-1783.
- Turner-McGrievy GM, Barnard ND, Cohen J, Jenkins DJ, Gloede L, Green AA. Changes in nutrient intake and dietary quality among participants with type 2 diabetes following a low-fat vegan diet or a conventional diabetes diet for 22 weeks. J Am Diet Assoc. 2008;108:1636-1645.
- Barnard ND, Cohen J, Jenkins DJ, et al. A low-fat vegan diet and a conventional diabetes diet in the treatment of type 2 diabetes: a randomized, controlled, 74-wk clinical trial. Am J Clin Nutr. 2009;89:1588S-1596S.
- Barnard ND, Noble EP, Ritchie T, et al. D2 dopamine receptor Taq1A polymorphism, body weight, and dietary intake in type 2 diabetes. Nutrition. 2009;25:58-65.
- Barnard ND, Gloede L, Cohen J, et al. A low-fat vegan diet elicits greater macronutrient changes, but is comparable in adherence and acceptability, compared with a more conventional diabetes diet among individuals with type 2 diabetes. J Am Diet Assoc. 2009;109:263-272.
Menstrual Pain Study
In a crossover design, 33 women followed a low-fat, vegetarian diet for two menstrual cycles. For two additional cycles, they followed their customary diet while taking a supplement placebo pill. Dietary intake, serum sex-hormone binding globulin concentration, body weight, pain duration and intensity, and premenstrual symptoms were assessed during each study phase. A low-fat vegetarian diet was associated with increased serum sex-hormone binding globulin concentration and reductions in body weight, dysmenorrhea duration and intensity, and premenstrual symptom duration.
- Barnard ND, Scialli AR, Hurlock D, Bertron P. Diet and sex-hormone binding globulin, dysmenorrhea, and premenstrual symptoms. Obstet Gynecol. 2000;95:245-250.
- Barnard ND, Scialli AR, Bertron P, Hurlock D, Edmonds K, Talev L. Effectiveness of a low-fat vegetarian diet in altering serum lipids in healthy premenopausal women. Am J Cardiol. 2000;85:969-972.
In an outpatient setting, 64 overweight, postmenopausal women were randomly assigned to a low-fat, plant-based diet or a control diet based on National Cholesterol Education Program guidelines, without energy intake limits, and were asked to maintain exercise unchanged. Dietary intake, body weight and composition, resting metabolic rate, thermic effect of food, and insulin sensitivity were measured at baseline and 14 weeks. Adoption of a low-fat, plant-based diet was associated with significant weight loss in overweight postmenopausal women, despite the absence of prescribed limits on portion size or energy intake.
- Barnard ND, Scialli AR, Turner-McGrievy G, Lanou AJ, Glass J. The effects of a low-fat, plant-based dietary intervention on body weight, metabolism, and insulin sensitivity. Am J Med. 2005;118:991-997.
- Turner-McGrievy GM, Barnard ND, Scialli AR, Lanou AJ. Effects of a low-fat vegan diet and a Step II diet on macro- and micronutrient intakes in overweight postmenopausal women. Nutrition. 2004;20:738-746.
- Turner-McGrievy GM, Barnard ND, Scialli AR. A two-year randomized weight loss trial comparing a vegan diet to a more moderate low-fat diet. Obesity (Silver Spring). 2007;15:2276-2281.
GEICO I Study
At two corporate sites of the Government Employees Insurance Company (GEICO), employees who were either overweight (BMI ≥ 25 kg/m2) and/or had type 2 diabetes participated in a 22-week, worksite-based dietary intervention study. At the intervention site, participants were asked to follow a low-fat, plant-based diet and participate in weekly group meetings that included instruction and group support. At the control site, participants received no instruction and made no diet changes.
- Ferdowsian HR, Barnard ND, Hoover VJ, et al. A multicomponent intervention reduces body weight and cardiovascular risk at a GEICO corporate site. Am J Health Promot. 2010;24:384-387.
- Levin SM, Ferdowsian HR, Hoover VJ, Green AA, Barnard ND. A worksite programme significantly alters nutrient intakes. Public Health Nutr. 2010;13:1629-1635.
- Katcher HI, Ferdowsian HR, Hoover VJ, Cohen JL, Barnard ND. A worksite vegan nutrition program is well-accepted and improves health-related quality of life and work productivity. Ann Nutr Metab. 2010;56:245-252.
- Turner-McGrievy GM, Jenkins DJ, Barnard ND, Cohen J, Gloede L, Green AA. Decreases in dietary glycemic index are related to weight loss among individuals following therapeutic diets for type 2 diabetes. J Nutr. 2011;141:1469-1474.
GEICO II Study
In our second GEICO study, 292 GEICO employees in 10 sites across the country who were either overweight (BMI ≥ 25 kg/m2) and/or had type 2 diabetes participated in an 18-week worksite-based dietary intervention study. At the intervention site, participants were asked to follow a low-fat plant-based diet and participate in weekly group meetings that included instruction and group support (intervention group). At the control site, participants received no instruction and made no diet changes (control group). Weight, serum lipid concentration and glycemic control were measured at baseline and 18 weeks.
- Agarwal U, Mishra S, Xu J, Levin S, Gonzales J, Barnard ND. A Multicenter Randomized Controlled Trial of a Nutrition Intervention Program in a Multiethnic Adult Population in the Corporate Setting Reduces Depression and Anxiety and Improves Quality of Life: The GEICO Study. Am J Health Promot. 2015;29:245-54.
- Mishra S, Xu J, Agarwal U, Gonzales J, Levin S, Barnard ND. A multicenter randomized controlled trial of a plant-based nutrition program to reduce body weight and cardiovascular risk in the corporate setting: the GEICO study. Eur J Clin Nutr. 2013;67:718-724.
- Mishra S, Barnard ND, Gonzales J, Xu J, Agarwal U, Levin S. Nutrient intake in the GEICO multicenter trial: the effects of a multicomponent worksite intervention. Eur J Clin Nutr. 2013;67:1066-1071.
The study assigned 42 adult migraine sufferers to either consume a low-fat plant-based diet or take a placebo supplement for 16 weeks. Participants then switched groups for a second 16-week period. During the diet period, participants consumed a plant-based diet and then an elimination diet to remove foods that are common migraine pain triggers. The severity of the worst headache pain improved significantly during the plant-based diet period, compared to the supplement period.
- Bunner AE, Agarwal U, Gonzales JF, Valente F, Barnard ND. Nutrition intervention for migraine: a randomized crossover trial. J Headache Pain. 2014 Oct 23;15:69
Reviews, Editorials, and Additional Research
Kahleova H, Klementova M, Herynek V, et al. The effect of a vegetarian vs conventional hypocaloric diabetic diet on thigh adipose tissue distribution in subjects with type 2 diabetes: a randomized study. J Am Coll Nutr. 2018;36:364-369.
Barnard ND, Willett WC, Ding EL. The misuse of meta-analysis in nutrition research. JAMA. 2017;318:1435-1436.
Yokoyama Y, Levin SM, Barnard ND. Association between plant-based diets and plasma lipids: a systematic review and meta-analysis. Nutr Rev. 2017;75:683-698.
Kahleova H, Levin S, Barnard N. Cardio-metabolic benefits of plant-based diets. Nutrients. 2017; 9. pii: E848.
Kahleova H, Lloren JI, Mashchak A, Hill M, Fraser GE. Meal frequency and timing are associated with changes in body mass index in Adventist Health Study 2. J Nutr. 2017;147:1722-1728.
Freeman AM, Morris PB, Barnard N, et al. Trending cardiovascular nutrition controversies. J Am Coll Cardiol. 2017;69:1172-1187.
Barnard ND, Levin SM, Yokoyama Y. A systematic review and meta-analysis of changes in body weight in clinical trials of vegetarian diets. J Acad Nutr Diet. 2015;115:954-969.
Yokoyama Y, Barnard ND, Levin SM, Watanabe M. Vegetarian diets and glycemic control in diabetes: a systematic review and meta-analysis. Cardiovasc Diagn Ther. 2014;4:373-82.
Barnard ND, Bunner AE, Agarwal U. Saturated and trans fats and dementia: a systematic review. Neurobiol Aging. 2014;35(Suppl 2):S65-73.
Barnard ND, Bush AI, Ceccarelli A, et al. Dietary and lifestyle guidelines for the prevention of Alzheimer's disease. Neurobiol Aging. 2014;35(Suppl 2):S74-78.
Yokoyama Y, Nishimura K, Barnard ND, et al. Vegetarian diets and blood pressure: a meta-analysis. JAMA Intern Med. 2014;174:577-587.
Gonzales JF, Barnard ND, Jenkins DJ, Lanou AJ, Davis B, Saxe G, Levin S. Applying the precautionary principle to nutrition and cancer. J Am Coll Nutr. 2014;33:239-246.
Barnard ND. The physician's role in nutrition-related disorders: from bystander to leader. Virtual Mentor. 2013;15:367-372.
Agarwal U. Rethinking red meat as a prevention strategy for iron deficiency. Infant, Child, & Adolescent Nutrition. 2013;5:231-235.
Trapp CB, Barnard ND. Usefulness of vegetarian and vegan diets for treating type 2 diabetes. Curr Diab Rep. 2010;10:152-158.
Trapp C, Barnard N, Katcher H. A plant-based diet for type 2 diabetes: scientific support and practical strategies. Diabetes Educ. 2010;36:33-48.
Berkow SE, Barnard N, Eckart J, Katcher H. Four therapeutic diets: adherence and acceptability. Can J Diet Pract Res. 2010;71:199-204.
Barnard ND. Trends in food availability, 1909-2007. Am J Clin Nutr. 2010;91:1530S-1536S.
Lanou AJ. Should dairy be recommended as part of a healthy vegetarian diet? Am J Clin Nutr. 2009;89:1638S-1642S.
Barnard ND, Levin S. Vegetarian diets and disordered eating. J Am Diet Assoc. 2009;109:1523; author reply 1523-1524.
Spencer EH, Ferdowsian HR, Barnard ND. Diet and acne: a review of the evidence. Int J Dermatol. 2009;48:339-347.
Ferdowsian HR, Barnard ND. Effects of plant-based diets on plasma lipids. Am J Cardiol. 2009;104:947-956.
Barnard ND, Katcher HI, Jenkins DJ, Cohen J, Turner-McGrievy G. Vegetarian and vegan diets in type 2 diabetes management. Nutr Rev. 2009;67:255-263.
Lanou AJ, Barnard ND. Dairy and weight loss hypothesis: an evaluation of the clinical trials. Nutr Rev. 2008;66:272-279.