Mediterranean diet reduces risk of death in women by 20%

Researchers from Brigham and Women's Hospital have identified and evaluated mechanisms that may explain the 23% reduction in all-cause mortality risk in women associated with the Mediterranean diet.

The health benefits of the Mediterranean diet have been demonstrated in several studies, but long-term data on its effects on women in the U.S. are limited, and little is known about why the diet may reduce the risk of death. In a new study that followed more than 25,000 initially healthy U.S. women for up to 25 years, researchers at Brigham and Women's Hospital found that participants who followed the Mediterranean diet had a 23% lower risk of all-cause mortality, including reduced deaths from cancer and cardiovascular disease.

The researchers found evidence of biological changes that could explain this effect: They recorded changes in biomarkers of metabolism, inflammation, insulin resistance, and other processes. The results are published in the journal JAMA.

“For women who want to live longer, our study says: Watch your diet. The good news is that following a Mediterranean diet can reduce your risk of dying by about a quarter over 25 years, with benefits for both cancer and cardiovascular disease, the leading causes of death in women (and men) in the U.S. and around the world,” said senior study author Samia Mora, MD, a cardiologist and director of the Lipidometabolomics Center at Brigham and Women’s Health.

The Mediterranean diet is a varied plant-based diet rich in nuts, seeds, fruits, vegetables, whole grains, and legumes. The main source of fat is olive oil (usually extra virgin), and the diet includes moderate consumption of fish, poultry, dairy, eggs, and alcohol, and occasional consumption of meat, sweets, and processed foods.

This study examined the long-term benefits of following a Mediterranean diet in a U.S. population recruited through the Women's Health Research Project and explored the biological mechanisms that may explain the health benefits of this diet. The researchers assessed a panel of approximately 40 biomarkers representing various biological pathways and clinical risk factors.

Metabolic and inflammatory biomarkers made the largest contribution, followed by triglyceride-rich lipoproteins, obesity, and insulin resistance. Other biological pathways related to branched-chain amino acids, high-density lipoproteins, low-density lipoproteins, glycemic indices, and hypertension made smaller contributions.

“Our study provides important public health information: Even modest changes in established metabolic disease risk factors — particularly those related to small molecular metabolites, inflammation, triglyceride-rich lipoproteins, obesity, and insulin resistance — can yield significant long-term benefits from following a Mediterranean diet. This finding highlights the potential for encouraging healthier eating habits to reduce overall mortality risk,” said lead author Shafqat Ahmad, PhD, an associate professor of epidemiology at Uppsala University in Sweden and an investigator in the Center for Lipidometabolomics and the Division of Preventive Medicine at Brigham and Women’s Health.

The current study identifies important biological pathways that may help explain the reduction in all-cause mortality risk. However, the authors note some key limitations, including that the study was limited to middle-aged and older women with good education, who were mostly non-Hispanic and white. The study relied on food frequency questionnaires and other self-reported measures such as height, weight and blood pressure. But among the study’s strengths are its large size and long follow-up period.

The authors also note that as the concept of the Mediterranean diet has gained popularity, the diet has been adapted in different countries and cultures - but changes to the traditional diet can change its impact on health.

"Health professionals recognize the health benefits of the Mediterranean diet, and our study offers insight into why this diet may be so beneficial. Public health policies should promote the healthy nutritional qualities of the Mediterranean diet and discourage unhealthy adaptations," Mora said.