Diabetes and vegetarian diets

Should people with Type 2 Diabetes Mellitus (T2DM) follow a vegetarian diet? Here is what clinicians need to know.

Learn more about this topic in the HealthCert Professional Diploma program in Medical Nutrition Management – online nutrition training for GPs.

The prevalence of T2DM is steadily increasing worldwide, and it is a chronic disease largely caused by modifiable risk factors such as diet (1). Fortunately, this also means that diet and lifestyle changes are effective strategies for both the prevention and management of T2DM.

What is a vegetarian diet?

Vegetarian diets can take many forms. Lacto-ovo vegetarians exclude meat and fish, ovo-vegetarians exclude meat, fish and dairy, while lacto-vegetarians exclude meat, fish and eggs. Veganism is the strictest form of a vegetarian diet, which eliminates all animal products and by-products including eggs, dairy, and animal-derived ingredients. 

Regardless of the type of vegetarian diet, common characteristics of a well-planned vegetarian diet include a high intake of vegetables, fruits, whole grains, legumes, soy products, nuts and seeds. Typically, a vegetarian diet can reduce a person's intake of saturated fats and increase their intake of antioxidants, minerals, polyphenols, and fibre.

What does the research say about T2DM prevention?

Many studies have shown that diabetes may be prevented with a well-planned vegetarian diet. A 2017 systematic review and meta-analysis found that vegetarian diets were inversely associated with diabetes risk (2).

Studies that have looked at populations with a lifelong adherence to a vegetarian diet, such as Seventh Day Adventists, found a 74% reduced risk of developing diabetes compared to a diet with weekly meat consumption (3).

A study based in the Netherlands examined adherence to a plant-based diet and found that those who more closely adhered showed improved insulin resistance, lower risk of pre-diabetes, and a lower risk of developing T2DM (4).

Well-planned vegetarian diets may help prevent diabetes due to the high fibre content, which can bind to glucose and slow the absorption of glucose into the blood.

What does the research say about T2DM management?

Studies have found that among participants with T2DM, adopting a vegetarian diet can lead to a reduction in fasting plasma glucose levels, improved insulin sensitivity, and greater reductions in HbA1c levels (5,6,7).

Notably, some of these studies found vegetarian diets were more beneficial in improving diabetes symptoms than medication, and medication use significantly decreased once participants adopted a vegetarian diet (7).

Additionally, research shows that vegetarian diets may improve other health markers including blood pressure and serum cholesterol in comparison to an omnivorous diet (8,9).

There is ample research to suggest that vegetarian diets, and similar plant-based dietary patterns such as the Mediterranean Diet, are beneficial in the prevention and management of T2DM (10). While vegetarian diets may not be suitable for all people with T2DM, GPs are well-placed to educate patients on the benefits while considering the feasibility for the individual.

Learn more with the online HealthCert Professional Diploma program in Medical Nutrition Management.

– Sarah Marko, Accredited Practising Dietitian

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References

• Olfert MD, Wattick RA. Vegetarian Diets and the Risk of Diabetes. Curr Diab Rep. 2018 Sep 18;18(11):101. doi: 10.1007/s11892-018-1070-9. PMID: 30229314; PMCID: PMC6153574.
• Lee Y, Park K. Adherence to a Vegetarian Diet and Diabetes Risk: A Systematic Review and Meta-Analysis of Observational Studies. Nutrients. 2017 Jun 14;9(6):603. doi: 10.3390/nu9060603. PMID: 28613258; PMCID: PMC5490582.
• Vang A, Singh PN, Lee JW, Haddad EH, Brinegar CH. Meats, processed meats, obesity, weight gain and occurrence of diabetes among adults: findings from Adventist Health Studies. Ann Nutr Metab. 2008;52(2):96-104. doi: 10.1159/000121365. Epub 2008 Mar 18. Erratum in: Ann Nutr Metab. 2010;56(3):232. PMID: 18349528.
• Chen Z, Zuurmond MG, van der Schaft N, Nano J, Wijnhoven HAH, Ikram MA, Franco OH, Voortman T. Plant versus animal based diets and insulin resistance, prediabetes and type 2 diabetes: the Rotterdam Study. Eur J Epidemiol. 2018 Sep;33(9):883-893. doi: 10.1007/s10654-018-0414-8. Epub 2018 Jun 8. PMID: 29948369; PMCID: PMC6133017.
• Nicholson AS, Sklar M, Barnard ND, Gore S, Sullivan R, Browning S. Toward improved management of NIDDM: A randomized, controlled, pilot intervention using a lowfat, vegetarian diet. Prev Med. 1999 Aug;29(2):87-91. doi: 10.1006/pmed.1999.0529. PMID: 10446033.
• Barnard ND, Cohen J, Jenkins DJ, Turner-McGrievy G, Gloede L, Jaster B, Seidl K, Green AA, Talpers S. 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 Aug;29(8):1777-83. doi: 10.2337/dc06-0606. PMID: 16873779.
• Kahleova H, Matoulek M, Malinska H, Oliyarnik O, Kazdova L, Neskudla T, Skoch A, Hajek M, Hill M, Kahle M, Pelikanova T. Vegetarian diet improves insulin resistance and oxidative stress markers more than conventional diet in subjects with Type 2 diabetes. Diabet Med. 2011 May;28(5):549-59. doi: 10.1111/j.1464-5491.2010.03209.x. PMID: 21480966; PMCID: PMC3427880.
• Marrone G, Guerriero C, Palazzetti D, Lido P, Marolla A, Di Daniele F, Noce A. Vegan Diet Health Benefits in Metabolic Syndrome. Nutrients. 2021 Mar 2;13(3):817. doi: 10.3390/nu13030817. PMID: 33801269; PMCID: PMC7999488.
• Dinu M, Abbate R, Gensini GF, Casini A, Sofi F. Vegetarian, vegan diets and multiple health outcomes: A systematic review with meta-analysis of observational studies. Crit Rev Food Sci Nutr. 2017 Nov 22;57(17):3640-3649. doi: 10.1080/10408398.2016.1138447. PMID: 26853923.
• Papamichou D, Panagiotakos DB, Itsiopoulos C. Dietary patterns and management of type 2 diabetes: A systematic review of randomised clinical trials. Nutr Metab Cardiovasc Dis. 2019 Jun;29(6):531-543. doi: 10.1016/j.numecd.2019.02.004. Epub 2019 Feb 25. PMID: 30952576