ADA News: how can we put the brakes on Type 2 diabetes? – by Emily Burns

Emily BurnsWe know that the best way to reduce your risk of Type 2 diabetes is to eat well and move more. But with the numbers of people living with Type 2 diabetes on the rise, scientists are searching for new ways to lower risk.

In the first news update from this year’s American Diabetes Association Scientific Sessions, we take a closer look at Type 2 prevention – from the perspective of both new clinical trials and studies in the past.

Vitamin D prevention trial comes up short

Previous research has suggested that people with low vitamin D levels have a higher risk of Type 2 diabetes. This in turn has led to the belief that vitamin D supplements could reduce the risk of Type 2.

But when we find associations between two things, like this, we need to be sure that they’re real. The best way to do that is to run a clinical trial: do vitamin D supplements reduce the number of people developing Type 2?

So that’s exactly what the D2D trial team did. They screened over 7,000 people to find around 2,400 at high risk of Type 2 diabetes. These 2,400 were recruited into the trial, with half taking 4,000 units of vitamin D each day and the other half taking a dummy pill. 

Three years later, they found that the levels of vitamin D in the group taking the supplements had doubled, while the levels in the placebo group stayed the same. So that’s a good start.

But, when it came to the number of people diagnosed with Type 2 diabetes during the study, there was no difference: 9.4 cases per year in the vitamin D group and 10.7 per year in the control group. Despite the lack of effect on Type 2 risk, the team found that this high level of vitamin D (much higher than usual supplements) was in fact safe.

Interestingly, there is an argument that the benefits of supplements would be greatest for those who were vitamin D deficient. In D2D, the majority had adequate levels of vitamin D at the start of the trial, but the researchers did find indications of a potential protective effect for the small number of participants who weren’t. They stressed more research would be needed to explore this.

A disappointing result perhaps, but negative results are really important. We now know that while vitamin D supplements are safe, for the majority of people they don’t appear to protect against Type 2.

The full results of this trial have been published.

A global PREVIEW of Type 2 prevention efforts

PREVIEW is a global study – across Canada, Australia, New Zealand and Europe – that aims to find out if high protein diets can help to reduce the risk of Type 2 diabetes.

Some background first. The Finland Diabetes Prevention Study and the US Diabetes Prevention Program both demonstrated that lifestyle interventions (diet and exercise) could significantly reduce the number of people who went on to develop Type 2 diabetes. Alongside this, the DioGENES study (involving people who were obese and didn’t have Type 2) suggested that a high protein/low GI diet was the best option for helping people to maintain weight loss.

Based on these findings, PREVIEW asked: could a lifestyle intervention involving a high protein/low GI diet help to prevent Type 2 in people at high risk? To answer the question, they recruited 2,500 people into their trial. They initially screened 15,000 people via medical records, and then 5,000 face-to-face (phew).

Before being randomly assigned to four programmes – each one testing a combination of a moderate or high protein diet with moderate or high intensity exercise – everyone took part in an eight-week low-calorie meal replacement phase. Nearly 80% of the participants lost an average of 10 kilos.

After three years on the programme, the team found that there was no difference in the risk of Type 2 between the four groups. The high protein/low GI diet didn’t appear to be superior. But, they also found that only 4% of the participants developed Type 2 diabetes. This was much lower than they were expecting (around 15%), which is really impressive.

So why was it so low? The first, and optimistic, theory is that the low-calorie phase – resulting in a rapid weight loss – played an important role. This opens up questions around whether low-calorie meal replacements (or other approaches to rapid weight loss) could be considered as prevention strategies.

But (there’s always a but), there are a couple of reasons to be cautious. First, they didn’t have any control groups – a group not taking part in the intervention at all, or a group skipping the low-calorie phase. This means that they don’t know how many people would have developed Type 2 on their own, or how much the low-calorie phase played a role.

Second, around half of the participants dropped out over the course of the trial, lowering the numbers in each of the four programmes from around 500 to 250. And the team don’t know how many of those who dropped out went on to develop Type 2 diabetes.

30 years on from the Chinese prevention study

 The 1986 Da Qing Diabetes Prevention Study recruited 540 people in China at high risk of Type 2 diabetes. The researchers wanted to see if lifestyle improvements (diet, exercise, or both) could reduce the number who went on to develop the condition.

In short, it worked. After six years, just under half (44%) of those taking part in lifestyle programmes developed Type 2 diabetes, compared to two thirds (67%) of the control group. 30 years later, the team went back to look at how many of the original participants developed complications of diabetes: cardiovascular disease, eye disease, kidney disease and nerve damage.

They found that people who didn’t develop Type 2 during the six-year trial had a much lower risk of diabetes complications today. Their risk of cardiovascular disease was roughly a third lower, and their risk of other complications was just under two thirds lower.

This suggests that delaying a diagnosis of Type 2 diabetes by six years or more could significantly reduce the risk of diabetes complications later in life, providing us with more important evidence that the longer we delay Type 2, the better that person’s health.

Keep an eye out for the next blog in our series of ADA news round-ups.

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