One of the best diets for health continues to improve.
A new study that followed more than 25,000 women for a quarter of a century found that the more in sync their eating patterns were with the Mediterranean diet, the less likely they were to die during that period. The relationship held even when the researchers took into account other factors that influence longevity, such as age, exercise habits and smoking history.
The findings were published Friday in the journal JAMA Network Open.
The Mediterranean diet is based on fruits, vegetables and whole grains. Extra virgin olive oil, rich in antioxidants, is the main source of fat. Protein comes from lean sources such as beans, legumes, and nuts, as well as fish, poultry, eggs, and low-fat or fat-free dairy. Wine is welcome in low to moderate amounts, while red and processed meats, butter, and sweets are eaten in moderation or not at all.
The diet has long been a favorite of doctors, nutritionists and weight loss programs. Studies consistently show that it helps people lose weight, lower cholesterol and blood pressure, all of which reduce the risk of cardiovascular disease. It also helps people control blood sugar and prevent type 2 diabetes.
How exactly does the Mediterranean diet achieve this? That's what Shafqat Ahmad, who studies the development of cardiovascular diseases at Sweden's Uppsala University and Harvard Medical School, and his colleagues wanted to find out.
They turned to the Women's Health Study, which involved tens of thousands of health professionals at least 45 years old. When the women joined the study in the mid-1990s, they answered 131 questions about the foods they ate.
The researchers used those responses to give each woman a score between 0 and 9 that reflected the extent to which they followed the Mediterranean diet. If they were above the median in terms of consumption of vegetables, fruits, nuts, whole grains, legumes or fish, they got one point. The same thing happens if they were above the median in their proportion of monounsaturated (which are good) and saturated (which are bad) fatty acids.
If women were below the median in their consumption of red and processed meats, they earned another point. And if they consumed between 5 and 15 grams of alcohol per day (the equivalent of a glass of wine or a can of beer) they also got a point.
Those with total scores between 0 and 3 were categorized as having “low” adherence to the Mediterranean diet. A total of 4 or 5 was classified as “intermediate” and a sum between 6 and 9 was considered “high.”
The Women's Health Study ended in 2004, but researchers continued to check in with participants once a year. Ahmad and his colleagues focused on the 25,315 women who had data on diet and a series of biomedical measurements since they entered the study.
By November 2023, 3,879 of the women had died. But the risk of being among them was not the same for everyone.
Compared with women in the low adherence group, those in the intermediate group were 16% less likely to die during the study period, while the risk of death for those with higher adherence to the Mediterranean diet was 23% lower , according to the study.
When researchers controlled for smoking, physical activity, alcohol consumption and menopausal factors, women in the intermediate group had an 8 percent lower risk of death, and those in the high group had an 11 percent lower risk of death. lower percent.
In addition to a reduced risk of death from any cause, following the Mediterranean diet was associated with a lower risk of dying from cancer or cardiovascular disease, said Dr. Samia Mora, a cardiologist at Brigham and Women's Hospital in Boston and lead author of the study. .
As for why the Mediterranean diet seemed to protect against premature death, the most influential factor (among the roughly 40 biomarkers the researchers were able to test) was a group of metabolites that seemed to explain 14.8% of the benefit. Ahmad and his colleagues drew special attention to higher levels of a useful amino acid called alanine, as well as lower levels of another amino acid called homocysteine, which is elevated in people with heart disease.
Inflammation accounted for 13% of the mortality benefit enjoyed by those with high adherence to the Mediterranean diet. Chronic inflammation is associated with a variety of health problems, including cardiovascular disease, diabetes, and some cancers.
A woman's body mass index and a measure of how well her body processes triglycerides were each responsible for 10.2% of the reduced risk of death, and insulin resistance accounted for 7.4%. .
The study suggests that making even modest improvements in these factors could help people achieve greater longevity outside of the Mediterranean diet, Ahmad said.
But he and Mora added that there must be other biological mechanisms at work that their study could not measure. They said the gut microbiome may be one of them.
Dr. Frank Hu, a professor of nutrition and epidemiology at the Harvard TH Chan School of Public Health, said the study offers “new insights” into why people who adopt the Mediterranean diet tend to live longer.
“This suggests that the health benefits of reducing mortality are explained by its effects on harmful blood metabolites, inflammation, insulin resistance and body weight, rather than by reducing total and LDL cholesterol,” he said. Hu, who was not involved in the work.
The study comes with several caveats, including the fact that 96% of the participants were white women. That means the results may not generalize to the general population.
Additionally, the women were asked about their eating habits only once, so there is no way to know if their diets changed as they grew older.
However, Mercedes Sotos Pietro, a nutritional epidemiologist at the Autonomous University of Madrid, said the findings on the reduced risk of death are in line with research she has conducted using data from the Nurses' Health Study and the Nurses' Follow-up Study. Health professionals who evaluated diet several times.
Pietro Sotos, who did not work on the new study, said the Mediterranean diet is “golden” because it includes a variety of tasty foods and prohibits nothing. That makes it easier for people to keep doing it for a long time, he said.
Hu added that the diet's flexibility makes it adaptable to many cuisines.
“As an example, an Asian person could use tofu as a protein source and substitute brown rice for white rice,” he said. “People can incorporate traditional recipes from other cultures and locally available foods while maintaining the key principles of the MedDiet.”
