DO FERMENTED FOODS ASSIST IN THE PREVENTION AND MANAGEMENT OF DIABETES?

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Humans have been fermenting a wide variety of foods and beverages for around 10,000 years, as a way of prolonging their nutritional value and the enjoyment of a bountiful seasonal harvest, amongst other things. Even today, with our modern food preservation techniques, fermented vegetables, fruits, grains, meat, fish, eggs and dairy are still commonly consumed in most parts of the world.

Dairy foods like buttermilk, cheese and yoghurt are particularly popular as fermentation reduces milk’s lactose content, making it more easily digestible for people with varying degrees of lactose intolerance. Fermented dairy foods are nutrient-rich, being excellent sources of high-quality protein, vitamins A, B12 and riboflavin, and minerals calcium, potassium, magnesium, zinc and phosphorous, and they are also a major source of probiotic bacteria including Lactobacillus delbrueckii subsp bulgaricus, Streptococcus thermophiles, Bifidobacterium and Lactobacillus strains.

Two recent systematic reviews have independently investigated the relationship between fermented foods in type 2 diabetes prevention and management.

Fermented dairy foods and the risk of developing type 2 diabetes

Kui Zhang and colleagues looked at all of the available evidence from observational studies (cohort studies and case-control studies) published before December 31, 2020. They found 15 studies, with 485,992 participants and 20,207 new cases of diabetes. Regular consumption (defined as at least once per week) of any kind of fermented dairy food was associated with a modest reduction in diabetes risk of 7.5% overall. Regular consumption of yoghurt was associated with a greater risk reduction of 17.2%, however. Unfortunately, a sub-analysis of people that consumed fermented dairy daily was not performed.

Fermented foods in people with pre-diabetes and type 2 diabetes

Xiao-Feng Zhang and colleagues looked at all of the available evidence from randomised controlled trials published before June 21, 2022. They found 18 studies, with 843 participants with pre-diabetes (5 studies) or type 2 diabetes. Fermented foods included breads and other cereals, milks (cow and soy), yoghurt, soybeans, tempeh, cheonggukjang , ginseng, etc…Regular consumption of fermented foods had a statistically significant but clinically modest beneficial effect on fasting blood glucose (0.43 mg/dL or 0.02 mmol/L reduction) and HOMA insulin resistance (-0.26, P<0.05), but not glycated haemoglobin (0.07%, P>0.05). Similarly, regular consumption also reduced total cholesterol (0.29 mg/dL or 0.01 mmol/L reduction) and LDL (“bad”) cholesterol (0.3 mg/dL or 0.01 mmol/L reduction) modestly, but did not have an effect on HDL cholesterol or triglycerides. Finally, fermented foods reduced diastolic blood pressure by 0.25 mmHg, but had no effect on systolic blood pressure.

Collectively, these two systematic reviews and meta-analyses provide very modest evidence that consuming fermented foods regularly may reduce the risk of developing type 2 diabetes and help those with the condition to manage it. As is unfortunately too often the case, more high-quality research is needed to determine how much and how often people need to consume fermented foods to have any real clinical benefits for people with diabetes or those at risk.

Read more:

• Zhang and colleagues. Dose-Dependent Effect of Intake of Fermented Dairy Foods on the Risk of Diabetes: Results From a Meta-analysis. Can J Diabetes. 2022
• Zhang and colleagues. Fermented foods and metabolic outcomes in diabetes and prediabetes-A systematic review and meta-analysis of randomized controlled trials. Crit Rev Food Sci Nutr. 2023

Dr Alan Barclay, PhD, is a consultant dietitian and chef with a particular interest in carbohydrates and diabetes. He is author of Reversing Diabetes (Murdoch Books), and co-author of 40 scientific publications, The Good Carbs Cookbook (Murdoch Books), Managing Type 2 Diabetes (Hachette Australia) and The Ultimate Guide to Sugars and Sweeteners (The Experiment Publishing).