A low-carb vegan diet has the same health effects as a vegetarian diet, but at a much lower cost to the environment, according to new research from St. Michael’s Hospital.
The study, published in The American Journal of Clinical Nutrition, found that a low-carbohydrate vegan diet had a significantly lower potential carbon emission value than its high-carbohydrate vegetarian counterpart. Furthermore, the researchers found that the lower the potential carbon emission value of the diet, the larger the reduction in blood cholesterol.
At a time when people across the world are feeling the varying effects of climate change, the study shows the role of diet in both lowering carbon emissions and improving health outcomes.
“We showed that you actually reduce greenhouse gas emissions, with a diet, that is effective, and that the reduction in greenhouse gas emissions is related to the fall in LDL cholesterol – often called the ‘bad’ cholesterol,” says principal author Dr. David Jenkins, director of the Clinical Nutrition and Risk Factor Modification Centre, and a scientist in the Li Ka Shing Knowledge Institute of St. Michael’s Hospital and a professor of Nutritional Sciences at the University of Toronto. “So as you reduce the impact of your diet on the environment, you also benefit by lowering your cholesterol.”
The researchers put people on two different types of plant-based diets: one was a low-carbohydrate vegan diet with no meat, dairy or eggs, supplemented with canola-oil enriched bread and high-protein vegan meat alternatives. This diet tried to reproduce the popular low carb diets that are traditionally high in meat and animal fats - but using plant ingredients.
The second diet was a vegetarian version of the clinical standard diet for lowering blood pressure, known as the Dietary Approaches to Stopping Hypertension diet or “DASH” diet, which included egg whites and low-fat dairy, but no meat. The diet is prescribed for the treatment of high blood pressure, diabetes, and other cardiovascular diseases. The diet participants of this study followed differed from the one that is normally prescribed as it cut out cholesterol sources.
The researchers then compared the effects of the diets on their subjects’ health as well as the carbon emission potential of each diet. They did so by using multiple different greenhouse gas emission databases, obtaining mean values for each food.
At the end of the three-month study period, they found that the two diets were similar in their effects on weight loss, reducing blood pressure, and blood cholesterol. Study participants on the vegan diet lost 5.9 kilos and those on the vegetarian diet lost 5.2 kilos.
Both groups also saw a reduction in hemoglobin A1c, a marker of glycemic control.
Jenkins says the study participants reduced their hemoglobin A1c by about one per cent, which is the type of reduction most drugs will produce. This means that the diets had a drug-like effect.
While the study was only over a three-month period, previous studies featuring participants with high cholesterol have shown that the participants have been able to maintain their weight loss after three months. This means that three months is a sufficient amount of time for metabolism to adapt to what the body is consuming.
Study participants were already healthy when the study began, which would have meant that further reductions in risk factors like blood cholesterol and blood pressure would be difficult. However, the study’s participants did see reductions in the risk factors on both the vegan and vegetarian diets.
“We have got to start changing the way we’re doing things in life,” says Dr. Jenkins. “This is just a small example that you can do it, it can be healthy. It is palatable. And you can reduce at least one risk factor, too.”
American Journal of Clinical Nutrition
Method of Research
Randomized controlled/clinical trial
Subject of Research
Low-carbohydrate vegan diets in diabetes for weight loss and sustainability: a randomized controlled trial
Article Publication Date
This study was funded by the Canola Council of Canada with additional funds from Loblaw Companies and major provision of simulated meat products from Loblaw Companies and Gardein Protein, Vancouver. The external funders and sponsors had no role in the design and conduct of the study; in the collection, analysis, and interpretation of the data; in the preparation, review, or approval of the manuscript; or in the decision to submit the manuscript for publication. DJAJ has received research grants from Saskatchewan & Alberta Pulse Growers Associations, the Agricultural Bioproducts Innovation Program through the Pulse Research Network, the Advanced Foods and Material Network, Loblaw Companies Ltd., Unilever Canada and Netherlands, Barilla, the Almond Board of California, Agriculture and Agri-food Canada, Pulse Canada, Kellogg's Company, Canada, Quaker Oats, Canada, Procter & Gamble Technical Centre Ltd., Bayer Consumer Care, Springfield, NJ, Pepsi/Quaker, International Nut & Dried Fruit Council (INC), Soy Foods Association of North America, the Coca-Cola Company (investigator initiated, unrestricted grant), Solae, Haine Celestial, the Sanitarium Company, Orafti, the International Tree Nut Council Nutrition Research and Education Foundation, the Peanut Institute, Soy Nutrition Institute (SNI), the Canola and Flax Councils of Canada, the Calorie Control Council, the Canadian Institutes of Health Research (CIHR), the Canada Foundation for Innovation (CFI)and the Ontario Research Fund (ORF). He has received in-kind supplies for trials as a research support from the Almond board of California, Walnut Council of California, the Peanut Institute, Barilla, Unilever, Unico, Primo, Loblaw Companies, Quaker (Pepsico), Pristine Gourmet, Bunge Limited, Kellogg Canada, WhiteWave Foods. He has been on the speaker's panel, served on the scientific advisory board and/or received travel support and/or honoraria from Nutritional Fundamentals for Health (NFH)-Nutramedica, Saint Barnabas Medical Center, The University of Chicago, 2020 China Glycemic Index (GI) International Conference, Atlantic Pain Conference, Academy of Life Long 390 Learning, the Almond Board of California, Canadian Agriculture Policy Institute, Loblaw Companies Ltd, the Griffin Hospital (for the development of the NuVal scoring system), the Coca-Cola Company, Epicure, Danone, Diet Quality Photo Navigation (DQPN), Better Therapeutics (FareWell), Verywell, True Health Initiative (THI), Heali AI Corp, Institute of Food Technologists (IFT), Soy Nutrition Institute (SNI), Herbalife Nutrition Institute (HNI), Saskatchewan & Alberta Pulse Growers Associations, Sanitarium Company, Orafti, the International Tree Nut Council Nutrition Research and Education Foundation, the Peanut Institute, Herbalife International, Pacific Health Laboratories, Barilla, Metagenics, Bayer Consumer Care, Unilever Canada and Netherlands, Solae, Kellogg, Quaker Oats, Procter & Gamble, Abbott Laboratories, Dean Foods, the California Strawberry Commission, Haine Celestial, PepsiCo, the Alpro Foundation, Pioneer Hi-Bred International, DuPont Nutrition and Health, Spherix Consulting and WhiteWave Foods, the Advanced Foods and Material Network, the Canola and Flax Councils of Canada, Agri-Culture and Agri-Food Canada, the Canadian Agri-Food Policy Institute, Pulse Canada, the Soy Foods Association of North America, the Nutrition Foundation of Italy (NFI), Nutra-Source Diagnostics, the McDougall Program, the Toronto Knowledge Translation Group (St. Michael's Hospital), the Canadian College of Naturopathic Medicine, The Hospital for Sick Children, the Canadian Nutrition Society (CNS), the American Society of Nutrition (ASN), Arizona State University, Paolo Sorbini Foundation and the Institute of Nutrition, Metabolism and Diabetes. He received an honorarium from the United States Department of Agriculture to present the 2013 W.O. Atwater Memorial Lecture. He received the 2013 Award for Excellence in Research from the International Nut and Dried Fruit Council. He received funding and travel support from the Canadian Society of Endocrinology and Metabolism to produce mini cases for the Canadian Diabetes Association (CDA). He is a member of the International 413 Carbohydrate Quality Consortium (ICQC). His wife, Alexandra L Jenkins, is a director and partner of INQUIS Clinical Research for the Food Industry, his 2 daughters, Wendy Jenkins and Amy Jenkins, hav published a vegetarian book that promotes the use of the foods described here, The Portfolio Diet for Cardiovascular Risk Reduction (Academic Press/Elsevier 2020 ISBN:978-0-12-810510- 8)and his sister, Caroline Brydson, received funding through a grant from the St. Michael's Hospital Foundation to develop a cookbook for one of his studies. He is also a vegan. BL has received funding from the Canadian Institutes for Health Research (ongoing), the Fonds de recherche du Québec – Santé (FRQS) (ongoing), Fonds de recherche du Québec – Nature et technologies (NT) (ongoing), the Ministère de la santé et des services sociaux (MSSS) du Québec (ongoing), Health Canada (completed in 2022) and Atrium Innovations (completed in 2019). He is an Advisory Board member of the Canadian Nutrition Society. MEK has received funding from a Toronto 3D Knowledge Synthesis and Clinical Trials foundation PhD scholarship award and is a part-time employee at Inquis Clinical Research, a contract research organization. CWCK has received grants or research support from the Advanced Food Materials Network, Agriculture and Agri-Foods Canada (AAFC), Almond Board of California, Barilla, Canadian Institutes of Health Research (CIHR), Canola Council of Canada, International Nut and Dried Fruit Council, International Tree Nut Council Research and Education Foundation, Loblaw Brands Ltd, the Peanut Institute, Pulse Canada and Unilever. He has received in-kind research support from the Almond Board of California, Barilla, California Walnut Commission, Kellogg Canada, Loblaw Companies, Nutrartis, Quaker (PepsiCo), the Peanut Institute, Primo, Unico, Unilever, WhiteWave Foods/Danone. He has received travel support and/or honoraria from the Barilla, California Walnut Commission, Canola Council of Canada, General Mills, International Nut and Dried Fruit Council, International Pasta Organization, Lantmannen, Loblaw Brands Ltd, Nutrition Foundation of Italy, Oldways Preservation Trust, Paramount Farms, the Peanut Institute, Pulse Canada, Sun-Maid, Tate & Lyle, Unilever and White Wave Foods/Danone. He has served on the scientific advisory board for the International Tree Nut Council, International Pasta Organization, McCormick Science Institute and Oldways Preservation Trust. He is a founding member of the International Carbohydrate Quality Consortium (ICQC), Executive Board Member of the Diabetes and Nutrition Study Group (DNSG) of the European Association for the Study of Diabetes (EASD), is on the Clinical Practice Guidelines Expert Committee for Nutrition Therapy of the EASD and is a Director of Glycemic Consulting and the Toronto 3D Knowledge Synthesis and Clinical Trials foundation. JLS has received research support from the Canadian Foundation for Innovation, Ontario Research Fund, Province of Ontario Ministry of Research and Innovation and Science, Canadian Institutes of health Research (CIHR), Diabetes Canada, PSI Foundation, Banting and Best Diabetes Centre (BBDC), American Society for Nutrition (ASN), INC International Nut and Dried Fruit Council Foundation, National Dried Fruit Trade Association, National Honey Board (the U.S. Department of Agriculture [USDA] honey “Checkoff” program), International Life Sciences Institute (ILSI), Pulse Canada, Quaker Oats Center of Excellence, The United Soybean Board (the USDA soy “Checkoff” program), The Tate and Lyle Nutritional Research Fund at the University of Toronto, The Glycemic Control and Cardiovascular Disease in Type 2 Diabetes Fund at the University of Toronto ( fund established by the Alberta Pulse Growers), and The Nutrition Trialists Fund at the University of Toronto (a fund established by an inaugural donation from the Calorie Control Council). He has received food donations to support randomized controlled trials from the Almond Board of California, California Walnut Commission, Peanut Institute, Barilla, Unilever/Upfield, Unico/Primo, Loblaw Companies, Quaker, 459 Kellogg Canada, WhiteWave Foods/Danone, Nutrartis, and Dairy Farmers of Canada. He has received travel support, speaker fees and/or honoraria from Diabetes Canada, Dairy Farmers of Canada, FoodMinds LLC, International Sweeteners Association, Nestlé, Pulse Canada, Canadian Society for Endocrinology and Metabolism (CSEM), GI Foundation, Abbott, General Mills, Biofortis, ASN, NorthernOntario School of Medicine, INC Nutrition Research & Education Foundation, European Food Safety Authority (EFSA), Comité Européen des Fabricants de Sucre (CEFS), Nutrition Communications, International Food Information Council (IFIC), Calorie Control Council, International Glutamate Technical Committee, and Physicians Committee for Responsible Medicine. He has or has had ad hoc consulting arrangements with Perkins Coie LLP, Tate & Lyle, Wirtschaftliche Vereinigung Zucker e.V., Danone, and Inquis Clinical Research. He is a member of the European Fruit Juice Association Scientific Expert Panel and former member of the Soy Nutrition Institute (SNI) Scientific Advisory Committee. He is on the Clinical Practice Guidelines Expert Committees of Diabetes Canada, European Association for the study of Diabetes (EASD), Canadian Cardiovascular Society (CCS), and Obesity Canada/Canadian Association of Bariatric Physicians and Surgeons. He serves or has served as an unpaid scientific advisor for the Food, Nutrition, and Safety Program (FNSP) and the Technical Committee on Carbohydrates of ILSI North America. He is a member of the International Carbohydrate Quality Consortium (ICQC), Executive Board Member of the Diabetes and Nutrition Study Group (DNSG) of the EASD, and Director of the Toronto 3D Knowledge Synthesis and Clinical Trials foundation. His wife is an employee of AB InBev. PJHJ, MMHA, DF, DP, SSP, MP BB, SCP, PP, FL, RB, TZ, 481 MP, GM, ST, VV, EJ, LAL and RGJ have no conflict of interest to declare.