Plant-based eating and diabetes

Diabetes is a serious, life changing condition and one of the major public health challenges of today. According to the International Diabetes Federation, almost half a billion people worldwide were living with diabetes in 2019 and this number is projected to increase 51% by 2045. Approximately 90% of these cases are type 2 diabetes (T2DM).(1)

Plant-based diets and type 2 diabetes

Plant-based eating is associated with a reduced incidence of T2DM. Diets consisting of whole grains, fruits, vegetables, legumes, and nuts with a moderate alcohol consumption and limited consumption of refined grains, red and processed meats, and sugar-sweetened beverages have been shown to reduce T2DM risk and improve blood-glucose management in individuals with T2DM.

This includes plant-based diets such as the Mediterranean Diet, DASH diet as well as healthy vegetarian and vegan diets. Key protective elements of these diets include a higher proportion of plant-based to animal-based proteins as well as a larger amount of monounsaturated and polyunsaturated fats than saturated and trans fats.(2)

In 2021, Pollakova et al. carried out a review of current scientific literature on the impact of a plant-based diet in the prevention and treatment of T2DM. They reviewed data from several large cohort studies with up to 20 years follow up. In the Adventist Health Study and the Oxford-EPIC study, the prevalence of T2DM was significantly lower amongst those adhering to a plant-based diet, with vegans having approximately a 50% lower chance of developing the condition, compared to omnivores. In the Nurses’ Health Study and the Rotterdam Study, high adherence to a plant-based diet reduced T2DM risk by 18-20%, when controlling for other lifestyle factors.(3)

The effects of eating pattern on T2D prevalence in the Adventists Health Study-2. Adapted from Trapp & Barnard 2010(4) Source: The Plant-Based Plan (Alpro Foundation report)

Plant-based eating and diabetes risk factors

Plant-based diets have been shown to improve glycemic control, body weight, and cardiometabolic risk factors in individuals with T2DM. A recent review of the efficacy and mechanisms of plant-based diets for treatment of T2DM highlighted the potential of plant-based eating patterns, in particular a low-fat vegan diet, to improve insulin sensitivity and reduce glycated hemoglobin (HbA1c) which is an indicator of poor blood-glucose management.(5)

A 2021 meta-analysis of randomized control trials (RCT) concluded that adherence to a plant-based diet reduced body weight (−2.54 kg, 95% CI: −4.16 to −0.92, p<0.001) and BMI (−0.91 kg/m2, 95% CI: −1.56 to −0.25, p<0.01) in participants with T2DM, in interventions greater than 16 weeks. The authors postulated that the lower energy-density and glycemic index, as well as the higher soluble fiber content of plant-based foods contributed to these results and that healthful plant-based dietary patterns can be supportive in the management of T2DM.(6)

Effect of plant-based protein on glycemic control

A systematic review and meta-analysis were conducted to evaluate the effect of the replacement of animal-based protein with plant-based protein on glycemic control in individuals with T2DM.(7) The meta-analysis included 13 RCT (total 280 patients with diabetes), with interventions lasting 8-weeks on average.

Diets emphasising a replacement of animal-based proteins (e.g., meat, dairy) with plant-based proteins (e.g., soya-based products, legumes, nuts) at a median level of 35% of total protein per day significantly lowered HbA1c and fasting glucose and insulin levels. Results from a more recent RCT, published in 2020, also showed that HOMA, a measure of insulin resistance and PREDIM, a measure of insulin sensitivity, were significantly improved during a 16-week plant-based dietary intervention (effect size –1.3 and 0.9, respectively).(8)

Therefore, replacing animal-based protein with protein from plant-based sources may be one dietary strategy that can be combined with standard therapy to help improve and manage glycaemic control in individuals with T2DM.

Changes in HbA1c (marker of long-term glucose control) – a meta-analyses of studies investigating Mediterranean, DASH, and vegetarian diets. HbA1c = glycosylated haemoglobin A1c. Adapted from: Kahleova H et al. 2019(9)

Conclusions

Plant-based dietary patterns, including vegan and vegetarian diets as well as diets with reduced animal-based protein consumption, are helpful in preventing and treating T2DM.