Plant-based diets made the headlines again this week, with coverage of a study suggesting a vegan diet can prevent type 2 diabetes. It was reported by the Daily Mail (‘Going vegan can prevent overweight adults from falling victim to diabetes’) and Medical News Today.
In the study, 75 participants were put into two groups. One group was asked to follow a low-fat, plant-based vegan diet with no calorie restriction. The other was asked to make no dietary changes for a period of 16 weeks. Participants prepared all their own meals and for both groups, alcoholic drinks were restricted to one per day for women and two per day for men.
All the participants had a Body Mass Index (BMI) between 28kg/m2 and 40kg/m2 (putting them into the ‘overweight’ or ‘obese’ categories), with no history of diabetes.
At the end of the study, the plant-based group reported:
- Marked improvements in beta-cell functioning – these are the cells which produce the hormone insulin, which is important for controlling blood sugar levels (a key factor in diabetes where blood sugar levels are elevated or harder to control).
- A significant increase in how well the body responded to insulin – when the body is less sensitive to the hormone insulin, it increases the chances of developing type 2 diabetes.
- A decrease in BMI and body fat levels – this is important because excess body weight is strongly associated with increased risk of type 2 diabetes.
It was reported that neither group made any changes to their physical activity regimen, nor did they change the use of their medications.
Behind the headlines: the Nutrilicious dietetic view
Whilst this is yet another study showing positive effects arising from a plant-based diet, we must be aware of its limitations:
- Efforts were made to help ensure adherence to the diet (such as dietitian telephone calls to the participants and food diaries completed at the start and end) but this still relies on the honesty and accuracy of the participant.
- As noted by the researchers, the participants used in the study were ‘generally health-conscious individuals’ who were willing to make significant dietary changes. Thus, we cannot be sure findings would be representative of the general population if they were to eat a vegan diet.
- The study is too short and too small to show conclusively that a vegan diet prevents type 2 diabetes.
- The meals were prepared by the participants and thus any changes or fluctuations were not controlled or recorded.
On the other hand, a strength of the study is that it was a randomised controlled trial, which is the gold standard in research for measuring the effectiveness of an intervention.
The link between plant-based diet and reduced risk of diabetes
The researchers recognised that the major factor accounting for the reduced risk of type 2 diabetes in the plant-based group was the weight lost (including visceral fat lost).
The link between the two is well established. Research shows that for every kilogram of weight loss, there is a 16% reduction in risk or type 2 diabetes.*
The generally higher fibre and lower fat content of plant-based diets (which also includes vegetarian diets) would be expected to be helpful in reducing the energy density, and thus total calorie content of the diet. This could help with reducing obesity.
*Hammam et al (2006) Effect of Weight Loss With Lifestyle Intervention on Risk of Diabetes.
In the UK, 11.9 million people are at risk of developing type 2 diabetes: prevention is clearly of great importance. The disease can have both short-term and long-term complications.
Further research will be needed to determine whether a vegan diet could prevent type 2 diabetes, and whether the positive improvements noted in this study require a strict vegan diet or whether the positive effects could be achieved with smaller changes.
Evidence shows the best ways to reduce risk of type 2 diabetes include:
- maintaining a healthy weight;
- eating healthily; and
- keeping physically active,
Adopting principles from a plant-based diet can certainly help with the first two points. The range of benefits of adopting a more plant-based diet are discussed further in last week’s blog.