Clinical Research

For more than 20 years, experts at the Physicians Committee for Responsible Medicine have been conducting and publishing clinical research in humans showing the wide-ranging health benefits of diet changes for conditions ranging from cardiovascular disease to rheumatoid arthritis, menopause to migraines, and weight loss to workplace productivity. 

Much of the Physicians Committee’s research has also focused on the benefits of a plant-based diet for type 2 diabetes. In a groundbreaking study funded by the National Institutes of Health, Physicians Committee President Neal Barnard, MD, FACC, and other researchers determined that a plant-based diet controlled blood sugar three times more effectively than a traditional diabetes diet that limited calories and carbohydrates. Within weeks on a plant-based diet, participants saw dramatic health improvements. They lost weight, insulin sensitivity improved, and HbA1c levels dropped. In some cases, you would never know they’d had the disease to begin with.

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.

Type 1 Diabetes

In this first randomized clinical trial to look at a vegan diet in people with type 1 diabetes, participants in the vegan diet group reduced the amount of insulin they needed to take by 28% and increased insulin sensitivity by 127%, compared with those following a portion-controlled diet. Body weight also decreased by about 11 pounds on average in the vegan group, compared with a nonsignificant change in body weight in the portion-controlled group.

“I was eating a low-carb, high-protein, high-meat diet, but the results were not good. Nothing was getting better—things were just getting worse,” says a participant who had been living with diabetes for decades was assigned to the vegan group. Following the study, he had better control of his blood sugar, his A1c came down dramatically, he lost about 23 pounds, and his stage 3 kidney disease has improved. “Before, I had very little hope. Because of the study, I now have hope.”

Kahleova H, Znayenko-Miller T, Smith K, et al. Effect of a dietary intervention on insulin requirements and glycemic control in type 1 diabetes: a 12-week randomized clinical trial. Clin Diabetes. 2024:cd230086. doi:10.2337/cd23-0086

Menopause

The WAVS trial—the Women’s Study for the Alleviation of Vasomotor Symptoms—found that a combination of following a plant-based diet, avoiding added oils, and adding a half-cup of soybeans daily reduced moderate to severe hot flashes by 88% and helped women lose, on average, 8 pounds in 12 weeks.

“The hot flashes were less frequent, and they were also less intense. I no longer had to change pajamas in the middle of the night due to sweating. The diet made me feel so much better. I have so much more energy, my skin is clearer, and I lost 20 pounds in 12 weeks.” – Margo, Study Participant

More Participant Success Stories: Anne Marie | Francine

Barnard ND, Kahleova H, Holtz DN, et al. A dietary intervention for vasomotor symptoms of menopause: a randomized, controlled trial. Menopause. 2023;30(1):80-87. doi:10.1097/GME.0000000000002080

Kahleova H, Znayenko-Miller T, Uribarri J, et al. Dietary advanced glycation end-products and postmenopausal hot flashes: a post-hoc analysis of a 12-week randomized clinical trial. Maturitas. 2023;172:32-38. doi:10.1016/j.maturitas.2023.03.008

Barnard ND, Kahleova H, Holtz DN, et al. The Women's Study for the Alleviation of Vasomotor Symptoms (WAVS): a randomized, controlled trial of a plant-based diet and whole soybeans for postmenopausal women. Menopause. 2021;28(10):1150-1156. doi: 10.1097/GME.0000000000001812

Rheumatoid Arthritis

The effects of diet changes on rheumatoid arthritis were investigated in a study that started with a low-fat vegan diet and then helped participants identify and eliminate additional pain trigger foods. The study led to reductions in pain and swelling, as well as an average weight loss of 14 pounds and reductions in total and LDL cholesterol.

“The symptoms of my rheumatoid arthritis went away completely. The aches in my shoulders are gone. I used to have them every night. In fact, all of my body ached at night, always. That’s gone.” – Jane, Study Participant

Barnard ND, Levin S, Crosby L, Flores R, Holubkov R, Kahleova H. A randomized, crossover trial of a nutritional intervention for rheumatoid arthritis. Am J Lifestyle Med. 2022;0(0). doi:10.1177/15598276221081819

Vegan Diet Versus Mediterranean Diet

A low-fat vegan diet led to an average weight loss of 13 pounds in 16 weeks, compared with no significant weight loss on the Mediterranean diet. The vegan diet also decreased total cholesterol by nearly 19 points, compared with only 3 points on the Mediterranean diet. While both diets lowered blood pressure, the Mediterranean diet actually had the edge for blood pressure lowering, perhaps due to polyphenols in olive oil.

“The vegan diet was way better for me. I lost more weight—about a pound a week—and was able to stop taking medicines for cholesterol, blood pressure, and heartburn. I think it was getting rid of all of the animal products and the dairy especially. And then eating low-fat, because on the Mediterranean diet you eat a lot of fat.” – Jenine, Study Participant

More Participant Success Stories: Helen | Jackie | Sean

In 2023, the Physicians Committee was awarded the Charles E. Ragus Award, which acknowledges an outstanding research paper published in the Journal of the American College of Nutrition, for the study.

Barnard ND, Alwarith J, Rembert E, et al. A Mediterranean diet and low-fat vegan diet to improve body weight and cardiometabolic risk factors: a randomized, cross-over trial. J Am Nutr Assoc. 2022;41(2):127-139. doi:10.1080/07315724.2020.1869625

Metabolism and Weight Loss

Participants followed either a low-fat vegan diet or made no dietary changes for 16 weeks. Researchers tracked body weight, body fat composition, insulin sensitivity, and the thermic effect of food at assessments at baseline and the end of study. The authors tracked intramyocellular lipid and hepatocellular lipid—the accumulating fat in muscle and liver cells that contributes to insulin resistance in a subset of participants. Those in the vegan group lowered their body weight by about 14 pounds and the fat inside the liver and muscle cells by 34% and 10%, respectively, and increased their metabolism by 18.7% compared to no significant changes in the control group.

Kahleova H, Petersen KF, Shulman GI, et al. Effect of a low-fat vegan diet on body weight, insulin sensitivity, postprandial metabolism, and intramyocellular and hepatocellular lipid levels in overweight adults: a randomized clinical trial. JAMA Netw Open. 2020;3(11):e2025454. doi:10.1001/jamanetworkopen.2020.25454

Acne

Spencer EH, Ferdowsian HR, Barnard ND. Diet and acne: a review of the evidence. Int J Dermatol. 2009;48(4):339-347. doi:10.1111/j.1365-4632.2009.04002.x

Aging

Kahleova H, Levin S, Barnard ND. Plant-based diets for healthy aging. J Am Coll Nutr. 2021;40(5):478-479. doi:10.1080/07315724.2020.1790442

Alzheimer’s Disease and Dementia

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. doi:10.1016/j.neurobiolaging.2014.03.033

Barnard ND, Bunner AE, Agarwal U. Saturated and trans fats and dementia: a systematic review. Neurobiol Aging. 2014;35(Suppl 2):S65-73. doi:10.1016/j.neurobiolaging.2014.02.030

Arthritis

Alwarith J, Kahleova H, Rembert E, et al. Nutrition interventions in rheumatoid arthritis: the potential use of plant-based diets. A review. Front Nutr. 2019;6:141. doi:10.3389/fnut.2019.00141

Cancer

Herby A, Cullimore J, Paul-Quinn J, Crosby L. Dairy intake and incidence of common cancers in prospective studies: a narrative review. International Journal of Disease Reversal and Prevention. 2023;5(1):14. doi:10.22230/ijdrp.2023v5n1a365

Gonzales JF, Barnard ND, Jenkins DJ, et al. Applying the precautionary principle to nutrition and cancer. J Am Coll Nutr. 2014;33(3):239-246. doi:10.1080/07315724.2013.866527

Cardiovascular Disease

Barnard ND, Rembert E, Freeman A, Bradshaw M, Holubkov R, Kahleova H. Blood type is not associated with changes in cardiometabolic outcomes in response to a plant-based dietary intervention. J Acad Nutr Diet. 2021;121(6):1080-1086. doi:10.1016/j.jand.2020.08.079

Viguiliouk E, Glenn AJ, Nishi SK, et al. Associations between dietary pulses alone or with other legumes and cardiometabolic disease outcomes: an umbrella review and updated systematic review and meta-analysis of prospective cohort studies. Adv Nutr. 2019;10(Suppl_4):S308-S319. doi:10.1093/advances/nmz113

Chiavaroli L, Nishi SK, Khan TA, et al. Portfolio dietary pattern and cardiovascular disease: a systematic review and meta-analysis of controlled trials. Prog Cardiovasc Dis. 2018;61(1):43-53. doi:10.1016/j.pcad.2018.05.004

Kahleova H, Levin S, Barnard ND. Vegetarian dietary patterns and cardiovascular disease. Prog Cardiovasc Dis. 2018;61(1):54-61. doi:10.1016/j.pcad.2018.05.002

Freeman AM, Morris PB, Barnard N, et al. Trending cardiovascular nutrition controversies. J Am Coll Cardiol. 2017;69(9):1172-1187. doi:10.1016/j.jacc.2016.10.086

Yokoyama Y, Levin SM, Barnard ND. Association between plant-based diets and plasma lipids: a systematic review and meta-analysis. Nutr Rev. 2017;75(9):683-698. doi:10.1093/nutrit/nux030

Kahleova H, Levin S, Barnard N. Cardio-metabolic benefits of plant-based diets. Nutrients. 2017;9(8):848. doi:10.3390/nu9080848

Yokoyama Y, Nishimura K, Barnard ND, et al. Vegetarian diets and blood pressure: a meta-analysis. JAMA Intern Med. 2014;174(4):577-587. doi:10.1001/jamainternmed.2013.14547

Ferdowsian HR, Barnard ND. Effects of plant-based diets on plasma lipids. Am J Cardiol. 2009;104(7):947-956. doi:10.1016/j.amjcard.2009.05.032

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(8):969-972. doi:10.1016/s0002-9149(99)00911-x

Childhood Nutrition

Flores R, Eckart J, Nash K, Kwitowski E. Implementation of vegan entrees in a Washington, D.C. elementary school. Journal of Child Nutrition and Management. 2019;43(2).

Agarwal U. Rethinking red meat as a prevention strategy for iron deficiency. Infant, Child, & Adolescent Nutrition. 2013;5:231-235. doi:10.1177/1941406413491285

Barnard ND. Trends in food availability, 1909-2007. Am J Clin Nutr. 2010;91(5):1530S-1536S. doi:10.3945/ajcn.2010.28701G

Clinical Practice

Stancic S, Cullimore J, Barnard N. Six applications of plant based diets for health promotion. Am J Lifestyle Med. 2022;16(4):434-438. doi:10.1177/15598276221104023

Barnard ND. The physician's role in nutrition-related disorders: from bystander to leader. Virtual Mentor. 2013;15(4):367-372. doi:10.1001/virtualmentor.2013.15.4.oped1-1304

Berkow SE, Barnard N, Eckart J, Katcher H. Four therapeutic diets: adherence and acceptability. Can J Diet Pract Res. 2010;71(4):199-204. doi:10.3148/71.4.2010.199

COVID-19

Kahleova H, Barnard ND. The role of nutrition in COVID-19: taking a lesson from the 1918 H1N1 pandemic. Am J Lifestyle Med. 2022;17(1):161-163. doi:10.1177/15598276221097621

Kahleova H, Barnard ND. Can a plant-based diet help mitigate Covid-19? Eur J Clin Nutr. 2022;76(7):911-912. doi:10.1038/s41430-022-01082-w

Stancic S, Cullimore J, Barnard ND. Shoring up vaccine efficacy. Am J Med. 2022;135(3):271-272. doi:10.1016/j.amjmed.2021.09.002

Kahleova H, Berrien-Lopez R, Holtz D, et al. Nutrition for hospital workers during a crisis: effect of a plant-based dietary intervention on cardiometabolic outcomes and quality of life in healthcare employees during the COVID-19 pandemic. Am J Lifestyle Med. 2021;16(3):399-407. doi:10.1177/15598276211050339

Crohn's Disease

Sandefur K, Kahleova H, Desmond AN, Elfrink E, Barnard ND. Crohn's disease remission with a plant-based diet: a case report. Nutrients. 2019;11(6):1385. doi:10.3390/nu11061385

Dairy Products

Cullimore JP, Herby AR, Paul-Quinn JL, Levin S, Stancic S. The nutritional content of animal and plant milks and their health implications. International Journal of Disease Reversal and Prevention. 2023;5(1):13. doi:10.22230/ijdrp.2023v5n1a363

Lanou AJ. Should dairy be recommended as part of a healthy vegetarian diet? Am J Clin Nutr. 2009; 89(5):1638S-1642S. doi:10.3945/ajcn.2009.26736P

Lanou AJ, Barnard ND. Dairy and weight loss hypothesis: an evaluation of the clinical trials. Nutr Rev. 2008; 66(5):272-279. doi:10.1111/j.1753-4887.2008.00032.x

Diabetes

Reynolds A, The Diabetes and Nutrition Study Group (DNSG) of the European Association for the Study of Diabetes (EASD). Evidence-based European recommendations for the dietary management of diabetes. Diabetologia. Published online April 17, 2023. doi:10.1007/s00125-023-05894-8

Jardine MA, Kahleova H, Levin SM, Ali Z, Trapp CB, Barnard ND. Perspective: plant-based eating pattern for type 2 diabetes prevention and treatment: efficacy, mechanisms, and practical considerations. Adv Nutr. 2021;12(6):2045-2055. doi:10.1093/advances/nmab063

Kahleova H, Carlsen B, Berrien Lopez R, Barnard ND. Plant-based diets for type 1 diabetes. J Diab Metab. 2020;11:847. doi:10.35248/2155-6156.20.11.847

Viguiliouk E, Kendall CW, Kahleová H, et al. Effect of vegetarian dietary patterns on cardiometabolic risk factors in diabetes: a systematic review and meta-analysis of randomized controlled trials. Clin Nutr. 2019;38(3):1133-1145. doi:10.1016/j.clnu.2018.05.032

Kahleova H, Tura A, Klementova M, et al. A plant-based meal stimulates incretin and insulin secretion more than an energy- and macronutrient-matched standard meal in type 2 diabetes: a randomized crossover study. Nutrients. 2019;11(3):486. doi:10.3390/nu11030486

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(5):364-369. doi:10.1080/07315724.2017.1302367

Barnard ND, Levin SM, Gloede L, Flores R. Turning the waiting room into a classroom: weekly classes using a vegan or a portion-controlled eating plan improve diabetes control in a randomized translational study. J Acad Nutr Diet. 2018;118(6):1072-1079. doi:10.1016/j.jand.2017.11.017

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(2):189. doi:10.3390/nu10020189

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(5):e158. doi:10.1038/nutd.2015.8

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(5):373-382. doi:10.3978/j.issn.2223-3652.2014.10.04

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(8):1469-1474. doi:10.3945/jn.111.140921

Trapp CB, Barnard ND. Usefulness of vegetarian and vegan diets for treating type 2 diabetes. Curr Diab Rep. 2010; 10(2):152-158. doi:10.1007/s11892-010-0093-7

Trapp C, Barnard N, Katcher H. A plant-based diet for type 2 diabetes: scientific support and practical strategies. Diabetes Educ. 2010; 36(1):33-48. doi:10.1177/0145721709357797

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(2):263-272. doi:10.1016/j.jada.2008.10.049

Barnard ND, Katcher HI, Jenkins DJ, Cohen J, Turner-McGrievy G. Vegetarian and vegan diets in type 2 diabetes management. Nutr Rev. 2009;67(5):255-263. doi:10.1111/j.1753-4887.2009.00198.x

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(5):1588S-1596S. doi:10.3945/ajcn.2009.26736H

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(1):58-65. doi:10.1016/j.nut.2008.07.012

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(10):1636-1645. doi:10.1016/j.jada.2008.07.015

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(8):1777-1783. doi:10.2337/dc06-0606

Endometriosis

Barnard ND, Holtz DN, Schmidt N, et al. Nutrition in the prevention and treatment of endometriosis: a review. Front Nutr. 2023;10:1089891. doi:10.3389/fnut.2023.1089891

Ketogenic Diets

Crosby L, Davis B, Joshi S, et al. Ketogenic diets and chronic disease: weighing the benefits against the risks. Front Nutr. 2021;8:702802. doi:10.3389/fnut.2021.702802

Menstrual Pain

Barnard ND, Scialli AR, Hurlock D, Bertron P. Diet and sex-hormone binding globulin, dysmenorrhea, and premenstrual symptoms. Obstet Gynecol. 2000;95(2):245-250. doi:10.1016/s0029-7844(99)00525-6

Migraine

Bunner AE, Agarwal U, Gonzales JF, Valente F, Barnard ND. Nutrition intervention for migraine: a randomized crossover trial. J Headache Pain. 2014;15(1):69. doi:10.1186/1129-2377-15-69

Nutrition Research

Barnard ND, Long MB, Ferguson JM, Flores R, Kahleova H. Industry funding and cholesterol research: a systematic review. Am J Lifestyle Med. 2019;15(2):165-172. doi:10.1177/1559827619892198

Barnard ND, Willett WC, Ding EL. The misuse of meta-analysis in nutrition research. JAMA. 2017;318(15):1435-1436. doi:10.1001/jama.2017.12083

Satiety

Klementova M, Thieme L, Haluzik M, et al. A plant-based meal increases gastrointestinal hormones and satiety more than an energy- and macronutrient-matched processed-meat meal in T2D, obese, and healthy men: a three-group randomized crossover study. Nutrients. 2019;11(1):157. doi:10.3390/nu11010157

Weight Loss

Barnard ND, Kahleova H. For appetite control, drugs vs diet. Am J Med. 2024;137(3):198-199. doi:10.1016/j.amjmed.2023.11.015

Crosby L, Rembert E, Levin S, et al. Changes in food and nutrient intake and diet quality on a low-fat vegan diet are associated with changes in body weight, body composition, and insulin sensitivity in overweight adults: a randomized clinical trial. J Acad Nutr Diet. 2022;122(10):1922-1939.e0. doi:10.1016/j.jand.2022.04.008

Kahleova H, Znayenko-Miller T, Uribarri J, Holubkov R, Barnard ND. Dietary advanced glycation products and their associations with insulin sensitivity and body weight: a 16-week randomized clinical trial. Obes Sci Pract. 2022;9(3):235-242. doi:10.1002/osp4.646

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(9):1722-1728. doi:10.3945/jn.116.244749

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(6):954-69. doi:10.1016/j.jand.2014.11.016

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(9):2276-2281. doi:10.1038/oby.2007.270

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(9):991-997. doi:10.1016/j.amjmed.2005.03.039

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(9):738-746. doi:10.1016/j.nut.2004.05.005

Workplace Wellness

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(4):245-254. doi:10.4278/ajhp.130218-QUAN-72

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(7):718-724. doi:10.1038/ejcn.2013.92

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(10):1066-1071. doi:10.1038/ejcn.2013.149

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(6):384-387. doi:10.4278/ajhp.081027-QUAN-255

Levin SM, Ferdowsian HR, Hoover VJ, Green AA, Barnard ND. A worksite programme significantly alters nutrient intakes. Public Health Nutr. 2010;13(10):1629-1635. doi:10.1017/S136898000999303X

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(4):245-252. doi:10.1159/000288281