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Clinical care/Education/Nutrition
Effect of oats and oat ß-glucan on glycemic control in diabetes: a systematic review and meta-analysis of randomized controlled trials
  1. Victoria Chen1,2,
  2. Andreea Zurbau1,2,
  3. Amna Ahmed1,2,
  4. Tauseef A Khan1,2,
  5. Fei Au-Yeung1,2,
  6. Laura Chiavaroli1,2,
  7. Sonia Blanco Mejia1,2,
  8. Lawrence A Leiter1,2,3,4,5,
  9. David J A Jenkins1,2,3,4,5,
  10. Cyril W C Kendall1,2,6,
  11. John L Sievenpiper1,2,3,4,5
  1. 1Department of Nutritional Sciences, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
  2. 2Toronto 3D Knowledge Synthesis and Clinical Trials Unit, Clinical Nutrition and Risk Factor Modification Center, St. Michael’s Hospital, Toronto, Ontario, Canada
  3. 3Li Ka Shing Knowledge Institute, St. Michael’s Hospital, Toronto, Ontario, Canada
  4. 4Division of Endocrinology and Metabolism, St. Michael’s Hospital, Toronto, Ontario, Canada
  5. 5Department of Medicine, Temerty Faculty of Medicine, University of Toronto, Toronto, Ontario, Canada
  6. 6College of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
  1. Correspondence to Dr John L Sievenpiper; john.sievenpiper{at}utoronto.ca

Abstract

Introduction Current health claims recognize the ability of oat ß-glucan to lower blood cholesterol; however, its ability to improve glycemic control is less certain. We undertook a systematic review and meta-analysis of randomized controlled trials (RCTs) to update the evidence on the effect of oats and oat ß-glucan on glycemic control in individuals with diabetes.

Research design and methods MEDLINE, EMBASE and Cochrane were searched (June 2021) for RCTs of ≥2 weeks investigating the effect of oat ß-glucan on glycemic control in diabetes. The outcomes were hemoglobin A1c (HbA1c), fasting glucose, 2-hour postprandial glucose (2h-PG) from a 75 g oral glucose tolerance test, homeostatic model assessment of insulin resistance (HOMA-IR) and fasting insulin. Independent reviewers extracted the data and assessed the risk of bias. Data were pooled using the generic inverse variance method. Heterogeneity was assessed (Cochran Q) and quantified (I2). Pooled estimates were expressed as mean difference (MD) with 95% CI. The certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development and Evaluations approach.

Results Eight trial comparisons (n=407) met the eligibility criteria. All trials were in adults with type 2 diabetes who were predominantly middle-aged, overweight and treated by antihyperglycemic medications or insulin. A median dose of 3.25 g of oat ß-glucan for a median duration of 4.5 weeks improved HbA1c (MD, −0.47% (95% CI −0.80 to −0.13), pMD=0.006), fasting glucose (−0.75 mmol/L (−1.20 to –0.31), pMD<0.001), 2h-PG (−0.42 mmol/L (−0.70 to –0.14), pMD=0.003) and HOMA-IR (−0.88 (−1.55 to –0.20), pMD=0.011). There was a non-significant reduction in fasting insulin (−4.30 pmol/L (−11.96 to 3.35), pMD=0.271). The certainty of evidence was high for fasting glucose, moderate for HOMA-IR and fasting insulin (downgraded for imprecision), and low for HbA1c and 2h-PG (downgraded for imprecision and inconsistency).

Conclusions Consumption of oats and oat ß-glucan results in generally small improvements in established markers of fasting and postprandial glycemic control beyond concurrent therapy in adults with type 2 diabetes. The current evidence provides a very good indication for reductions in fasting glucose and less of an indication for reductions in HbA1c, 2h-PG, fasting insulin and HOMA-IR in this population.

Trial registration number NCT04631913.

  • Diabetes Mellitus, Type 2
  • Nutritional Sciences

Data availability statement

Data are available upon reasonable request. Primary data files available upon request.

http://creativecommons.org/licenses/by-nc/4.0/

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

https://doi.org/10.1136/bmjdrc-2022-002784

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    Data availability statement

    Data are available upon reasonable request. Primary data files available upon request.

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    Footnotes

    • Contributors VC acquired the data, performed the data analysis, interpreted the data and drafted the manuscript. AA acquired the data and assisted with data analysis and interpretation. TAK and FA-Y assisted with data analysis and interpretation. AZ, CWCK and JLS were responsible for the conception and design of the study, acquired funding for the study, and guided data analysis and interpretation. All authors contributed to the critical revision of the manuscript for important intellectual content. JLS was responsible for overall study supervision and is the study guarantor. All authors approved the final version of the manuscript. The corresponding author attests that all listed authors meet the authorship criteria and that no others meeting the criteria have been omitted.

    • Funding This work was supported by an unrestricted grant from the Quaker Oats Center of Excellence. VC was funded by a University of Toronto Undergraduate Summer Research Award and Toronto 3D Summer Student Award. AZ was funded by a Banting & Best Diabetes Centre Fellowship in Diabetes Care (funded by Eli Lilly). AA was funded by a Toronto 3D MSc Scholarship Award. TAK was funded by a Toronto 3D Postdoctoral Fellowship Award. LC was funded by a Mitacs Elevate Postdoctoral Fellowship Award. JLS was funded by a Diabetes Canada Clinician Scientist Award.

    • Competing interests VC has received research support from the University of Toronto and Toronto 3D Knowledge Synthesis and Clinical Trials foundation. AZ is a part-time research associate at INQUIS Clinical Research, a contract research organization, and a consultant for Glycemic Index Foundation, a not-for-profit health promotion charity. She has received funding from the Banting & Best Diabetes Centre. AA has received funding from the Toronto 3D Knowledge Synthesis and Clinical Trials foundation. TAK has received research support from the Canadian Institutes of Health Research (CIHR), the International Life Sciences Institute (ILSI) and the National Honey Board. He has been an invited speaker at the Calorie Control Council annual meeting for which he has received an honorarium. He was received funding from the Toronto 3D Knowledge Synthesis and Clinical Trials foundation. FA-Y is a part-time research assistant at INQUIS Clinical Research, a contract research organization. LC was a Mitacs Elevate postdoctoral fellow jointly funded by the Government of Canada and the Canadian Sugar Institute. She was previously employed as a casual clinical coordinator at INQUIS Clinical Research (formerly Glycemic Index Laboratories), a contract research organization. DJAJ has received research grants from Saskatchewan Pulse Growers, the Agricultural Bioproducts Innovation Program through the Pulse Research Network, Advanced Foods and Materials Network, Loblaw Companies, Unilever, Barilla, Almond Board of California, Agriculture and Agri-Food Canada, Pulse Canada, Kellogg’s Company (Canada), Quaker Oats (Canada), Procter & Gamble Technical Centre, Bayer Consumer Care (Springfield, New Jersey, USA), Pepsi/Quaker, International Nut and Dried Fruit, Soyfoods Association of North America, Coca-Cola Company (investigator-initiated, unrestricted grant), Solae, Hain Celestial, Sanitarium Company, Orafti, International Tree Nut Council Nutrition Research and Education Foundation, Peanut Institute, Soy Nutrition Institute, Canola and Flax Councils of Canada, Calorie Control Council, Canadian Institutes of Health Research, Canada Foundation for Innovation, and Ontario Research Fund; has received in-kind supplies for trials as a research support from the Almond Board of California, Walnut Council of California, Peanut Institute, Barilla, Unilever, Unico, Primo, Loblaw Companies, Quaker (PepsiCo), Pristine Gourmet, Bunge, Kellogg Canada and WhiteWave Foods; has been on the speaker’s panel, served on the scientific advisory board or received travel support or honorariums from the Almond Board of California, Canadian Agriculture Policy Institute, Loblaw Companies, Griffin Hospital (for the development of the NuVal scoring system), Coca-Cola Company, EPICURE, Danone, Diet Quality Photo Navigation, Better Therapeutics (FareWell), Verywell, True Health Initiative, Institute of Food Technologists, Soy Nutrition Institute, Herbalife Nutrition Institute, Saskatchewan Pulse Growers, Sanitarium Company, Orafti, Almond Board of California, International Tree Nut Council Nutrition Research and Education Foundation, Peanut Institute, Herbalife International, Pacific Health Laboratories, Nutritional Fundamentals for Health, Barilla, Metagenics, Bayer Consumer Care, Unilever Canada and the Netherlands, Solae, Kellogg, Quaker Oats, Procter & Gamble, Abbott Laboratories, Dean Foods, California Strawberry Commission, Hain Celestial, PepsiCo, Alpro Foundation, Pioneer Hi-Bred International, DuPont Nutrition and Health, Spherix Consulting and WhiteWave Foods, Advanced Foods and Materials Network, Canola and Flax Councils of Canada, Agriculture and Agri-Food Canada, Canadian Agri-Food Policy Institute, Pulse Canada, Saskatchewan Pulse Growers, Soyfoods Association of North America, Nutrition Foundation of Italy, Nutrasource Diagnostics, McDougall Program, Toronto Knowledge Translation Group (St Michael’s Hospital), Canadian College of Naturopathic Medicine, The Hospital for Sick Children, Canadian Nutrition Society, American Society for Nutrition, Arizona State University, Paolo Sorbini Foundation, and the Institute of Nutrition, Metabolism and Diabetes; has received an honorarium from the US Department of Agriculture to present the 2013 WO Atwater Memorial Lecture and the 2013 Award for Excellence in Research from the International Nut and Dried Fruit Council; has received funding and travel support from the Canadian Society of Endocrinology and Metabolism to produce mini cases for the Canadian Diabetes Association; and is a member of the International Carbohydrate Quality Consortium. DJAJ’s wife, Alexandra L Jenkins, is a director and partner of Glycemic Index Laboratories, 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. CWCK has received grants or research support from the Advanced Foods and Materials Network, Agriculture and Agri-Food 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, 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), Peanut Institute, Primo, Unico, Unilever, and WhiteWave Foods/Danone. He has received travel support and/or honoraria from Barilla, California Walnut Commission, Canola Council of Canada, General Mills, International Nut and Dried Fruit Council, International Pasta Organisation, Lantmannen, Loblaw Brands, Nutrition Foundation of Italy, Oldways Preservation Trust, Paramount Farms, Peanut Institute, Pulse Canada, Sun-Maid, Tate & Lyle, Unilever and WhiteWave Foods/Danone. He has served on the scientific advisory board for the International Tree Nut Council, International Pasta Organisation, 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 the Toronto 3D Knowledge Synthesis and Clinical Trials foundation. JLS has received research support from the Canada Foundation for Innovation, Ontario Research Fund, Province of Ontario Ministry of Research, Innovation and Science, Canadian Institutes of Health Research (CIHR), Diabetes Canada, PSI Foundation, Banting & 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 US 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 (a 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 in-kind food donations to support a randomized controlled trial from the Almond Board of California, California Walnut Commission, Peanut Institute, Barilla, Unilever/Upfield, Unico/Primo, Loblaw Companies, Quaker, Kellogg Canada, WhiteWave Foods/Danone and Nutrartis. He has received travel support, speaker fees and/or honoraria from Diabetes Canada, Dairy Farmers of Canada, FoodMinds, International Sweeteners Association, Nestlé, Pulse Canada, Canadian Society of Endocrinology and Metabolism (CSEM), GI Foundation, Abbott, General Mills, Biofortis, ASN, Northern Ontario 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, and Physicians Committee for Responsible Medicine. He has or has had ad hoc consulting arrangements with Perkins Coie, Tate & Lyle, Wirtschaftliche Vereinigung Zucker eV, 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. SBM and LAL declare no competing interests.

    • Provenance and peer review Not commissioned; externally peer reviewed.

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