A follow-up study of 25,000 women for more than 20 years showed how this eating pattern contributes to reducing the risk of disease by 30%.
The Mediterranean diet – which is promoted as a “lifestyle” rather than diet – is known to have health benefits. In fact, there is scientific evidence about its protective effects, linked above all to the prevention of chronic diseases. Now, a large follow-up study conducted over more than 20 years of 25,000 women in the United States has shown the ways in which this eating pattern contributes to reducing the risk of diabetes.
The Mediterranean diet is rich in olive oil, fruits, vegetables, legumes, nuts and seeds and is a recommended way to reduce the risk of heart disease and diabetes mellitus (type 2), among others. But it was not clear exactly how and why it reduces the risk of type 2 diabetes, which is the most frequent (9 out of 10 cases in Argentina correspond to it).
To try to answer that question, researchers at Brigham and Women’s Hospital in the United States examined the results of more than 25,000 participants enrolled in the Women’s Health Study, a longitudinal cohort study that followed female health professionals for more than 20 years. .
In an article published in JAMA Network Open, report that women who adhered to a diet more similar to the Mediterranean had a rate of type 2 diabetes 30% lower than women who didn’t.
The team examined several biomarkers to search for biological explanations for these results and found key mechanisms including insulin resistance, body mass index, lipoprotein metabolism, and inflammation.
“Our findings support the idea that by improving their diet, people can improve their future risk of type 2 diabetes, particularly if they are overweight or obese,” says author Samia Mora, from Brigham’s Preventive Medicine and Cardiovascular Medicine divisions. and associate professor at Harvard Medical School.
“Much of the benefit that we see can be explained through a few avenues – he continues -. And it is important to note that many of these changes do not happen immediately, while metabolism can change in a short period of time, our study indicates that longer-term changes are taking place that can deliver protection for decades“.
The Women’s Health Study (WHS) enrolled female healthcare professionals between 1992 and 1995 and collected data through December 2017. It was designed to assess the effects of low-dose vitamin E and aspirin on the risk of heart disease and cancer .
Additionally, the participants were asked to complete food frequency questionnaires about dietary intake when the study began and to answer other questions about lifestyle, medical history, demographics, and more. More than 28,000 women provided blood samples at the beginning of the trial.
Mora and his colleagues took advantage of the data from the forms and blood samples to investigate the relationship between the Mediterranean diet, type 2 diabetes, and biomarkers that could explain the connection. To do this, they assigned each participant a Mediterranean diet intake score of 0 to 9, with points assigned for higher intake of fruits, vegetables, whole grains, legumes, nuts and fish, moderate intake of alcohol and lower intake of red or processed meats.
The team measured a variety of biomarkers, including traditional ones like cholesterol and more specialized ones that can only be detected by nucleic magnetic resonance imaging. These included lipoproteins, molecules that pack and transport fats and proteins, and measures of insulin resistance, a condition in which muscles, liver and fat cells do not respond to normal amounts of insulin.
Of the more than 25,000 participants in the WHS, 2,307 developed type 2 diabetes. Participants with a higher intake of the Mediterranean diet at the beginning of the study (scores greater than or equal to 6) developed diabetes at rates that were 30% lower than the participants with a lower intake of the Mediterranean diet (scores less than or equal to 3).
This effect was observed only among participants with a body mass index greater than 25 (overweight or obese range) and not among participants whose BMI was less than 25 (normal or underweight).
Insulin resistance biomarkers appeared to contribute the most to reducing risk, followed by biomarkers for body mass index, high-density lipoprotein measurements, and inflammation.
“Most of this reduced risk associated with the Mediterranean diet and type 2 diabetes was explained through biomarkers related to insulin resistance, adiposity, lipoprotein metabolism and inflammation,” explains first author Shafqat Ahmad, a researcher at the Molecular Epidemiology Unit at Uppsala University in Sweden, who helped conduct the study while working at Brigham. This knowledge may have important downstream consequences for the primary prevention of diabetes“.
Mora emphasizes that understanding the biology that explains how the Mediterranean diet can help protect against diabetes could be helpful in preventive medicine and for physicians who talk to patients about dietary changes.