Study: Mediterranean diet may reduce diabetes risk more than previously thought

Type 2 diabetes is a large and growing concern.

In the United Kingdom, the condition affects around 1 in 16 people. And in the United States, more than 1 in 10 people have it.

While medications can help people manage type 2 diabetes, preventing a disease is always better than treating it. So, scientists are looking for lifestyle changes that can reduce the risk.

A recent study in PLOS Medicine uses an interesting new technique to investigate the relationship between the Mediterranean diet and the risk of developing type 2 diabetes.

Diabetes and the Mediterranean diet

Experts generally consider the Mediterranean diet to be a healthy way to eat — it's rich in healthy fats and a variety of plant foods.

And some past studies have demonstrated possible links between this diet and a reduced risk of type 2 diabetes. 

For instance, a 2017 meta-analysis concluded that the Mediterranean diet has “a strong potential for preventing diabetes.” And a 2020 review reached similar conclusions.

But investigations had only found “modest” reductions in risk.

The study we’re covering today takes a fresh look at links between type 2 diabetes and the Mediterranean diet.

This time, the researchers have used an ingenious new method to get more accurate insights — at least in theory.

Facing a challenge

A challenge that affects many large-scale nutrition studies involves difficulty collecting data on what people eat. Scientists often rely on self-reported dietary information.

For instance, scientists might ask participants to write down what they’ve eaten over the last 24 hours. Although some people can accurately remember everything they’ve eaten, many can’t. 

Another common approach is to ask participants to fill out a food diary. But, again, it’s easy to imagine how someone might forget to add an item or maybe leave out a more indulgent snack.

So, getting a clear picture of how closely someone is following the Mediterranean diet can be quite difficult.

The authors of the latest study wanted to find a way around this issue. They set out to design a “nutritional biomarker score” for the Mediterranean diet.

What’s a nutritional biomarker?

When you digest a specific food, compounds from that food — or compounds produced when it’s digested — can make it into your bloodstream or be passed out in your pee. 

These compounds could theoretically be used as nutritional biomarkers.

So, if researchers test your blood or urine and find those compounds, it’s evidence that you ate that food.

If scientists can figure out biomarkers for individual foods, it might help make nutrition research more accurate. Biomarker data could replace or add to self-reported information.

However, finding biomarkers for individual foods is tricky. And finding a biomarker for a whole dietary pattern is even more challenging.

Designing a Mediterranean diet biomarker

To design a nutritional biomarker score for the Mediterranean diet, the authors of the recent paper used data from a study that had included 128 people.

Overall, 67 participants had received coaching on how to follow the Mediterranean diet.

The researchers also provided typical foods from the Mediterranean diet, like low-fat Greek yogurt, virgin olive oil, unsalted nuts, and canned legumes and tuna. 

The remaining 61 participants just got vouchers for their local grocery stores and no dietary guidance.

After 6 months, the scientists measured carotenoids and fatty acids in the blood of each participant.

Carotenoids are biomarkers of fruit and vegetable intake.

And the range of fatty acids in your blood is a marker of the types of fat you've consumed. 

Fatty acids help discern whether a person has eaten fish or shellfish, dairy, nuts, and other fats sources, like olive oil.

Using this data, the scientists behind the recent paper created a nutritional biomarker score for the Mediterranean diet consisting of 23 individual biomarkers.

Testing the biomarker score

Next, the scientists used this biomarker score to study the association between diet and the incidence of type 2 diabetes in a larger group of people. 

They used data from more than 22,202 people living in eight European countries — Denmark, France, Germany, Italy, the Netherlands, Spain, Sweden, and the United Kingdom. 

They followed these individuals for almost a decade. During this time, 9,453 participants developed type 2 diabetes.

The researchers found that participants with high nutritional biomarker scores for the Mediterranean diet were less likely to develop type 2 diabetes during the study period.

More specifically, they concluded that a 10% increase in the biomarker score was associated with an 11% lower risk of developing type 2 diabetes during the 10-year study.

These findings broadly agree with earlier research into diabetes and the Mediterranean diet. But the innovative scoring system did unearth some more food for thought.

A larger response

Alongside collecting the participants’ biomarker scores, the researchers also asked people to report their diets. 

The scientists analyzed diabetes risk using both the biomarker scores and the self-reported dietary information.

When they used the biomarker scores, the link between the Mediterranean diet and reduced diabetes risk was much stronger than when they used self-reported information.

So, the scores identified a stronger protective effect than the food diaries.

The authors also note that their biomarker analysis identified a much larger effect than similar studies in the past.

They compared their findings with earlier research that had calculated diabetes risk in participants who followed the Mediterranean diet most closely and those who followed it least closely.

The largest effect noted previously was that the group following the diet most closely had 25% fewer cases of type 2 diabetes than the group following it least closely. 

But in this latest study, when the researchers used the biomarker scores, they found 62% fewer cases — a substantial difference.

So, perhaps earlier studies had underestimated the anti-diabetes effect of following the Mediterranean diet.

Limitations and the future

Although the results are interesting, the study did have certain limitations. First and foremost, as with other studies of this nature, it can’t prove that the Mediterranean diet causes a reduced risk of diabetes.

Another issue, as the authors outline, is that changes in biomarkers might not be specific to the Mediterranean diet. It might just be a sign that participants had an overall healthier diet.

Also, the scientists controlled for a wide range of variables, including body mass index, age, other health conditions, level of education, and smoking status. But there’s always the chance that another factor had influenced the results.

Still, all in all, this is further evidence of the health benefits of the Mediterranean diet. It’s not definitive proof that it reduces the risk of type 2 diabetes, but the links are growing stronger.


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