The Mediterranean diet reduces the risk of death in women by 20%

Researchers at Brigham and Women's Hospital have identified and assessed mechanisms that may explain the 23% reduction in the risk of all-cause mortality 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 United States are limited, and little is known about the reasons why this diet may reduce the risk of death. In a new study that followed more than 25,000 initially healthy American women for up to 25 years, researchers from Brigham and Women's Hospital found that participants who followed a Mediterranean diet had a 23% lower risk of all-cause mortality, including a reduction in mortality from cancer and cardiovascular diseases.

The researchers found evidence of biological changes that may explain this effect: they documented changes in biomarkers of metabolism, inflammation, insulin resistance and other processes. The results were published in the journal JAMA.

“For women who want to live longer, our research says: watch your diet. The good news is that following a Mediterranean diet can reduce your risk of death by about a quarter over 25 years, with benefits in both reducing deaths from cancer and cardiovascular disease, which are the leading causes of death in women (and men) in the United States and around the world,” said senior study author Samia Mora, MD, a cardiologist and director of the Center for Lipid Metabolomics at the Brigham.

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 products, eggs and alcohol, and rare consumption of meat, sweets and processed foods.

This study examined the long-term benefits of following a Mediterranean diet in a US population recruited through the Women's Health Research Project and examined 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.

Biomarkers of metabolism and inflammation made the largest contribution, followed by triglyceride-rich lipoproteins, obesity, and insulin resistance. Other biological pathways related to branched amino acids, high-density lipoproteins, low-density lipoproteins, glycemic parameters and hypertension made smaller contributions.

“Our study provides significant information for public health: Even modest changes in established metabolic disease risk factors—especially those associated with small molecular metabolites, inflammation, triglyceride-rich lipoproteins, obesity, and insulin resistance—can bring significant long-term benefits from adherence Mediterranean diet. This finding highlights the potential of encouraging healthier eating habits to reduce overall mortality risk,” said lead author Shafqat Ahmad, PhD, assistant professor of epidemiology at Uppsala University in Sweden and a researcher in the Center for Lipid Metabolomics and Department of Preventive Medicine at the Brigham.

This study identifies important biological pathways that may help explain the reduced risk of all-cause mortality. However, the authors note some key limitations, including that the study was limited to well-educated, middle-aged and older women who were primarily 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 strengths of the study are its large scale 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 may change its health effects.

“Medical experts 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.