Numerous studies have reported the health benefits of the Mediterranean diet. However, long-term data on its effects have been limited, and the reasons behind its mortality risk reduction are not well understood.
In a new study following over 25,000 initially healthy women in the U.S. for up to 25 years, researchers from Brigham and Women’s Hospital found that higher adherence to the Mediterranean diet was associated with a 23% lower risk of all-cause mortality. This included reductions in both cancer and cardiovascular mortality. The researchers identified biological changes, including alterations in biomarkers of metabolism, inflammation, and insulin resistance, which may explain these benefits. The results are published in JAMA.
Study findings show that a Mediterranean dietary pattern could result in about a one-quarter reduction in the risk of death over more than 25 years, with benefits for both cancer and cardiovascular mortality, the top causes of death in women (and men) in the U.S. and globally.
The Mediterranean diet is plant-based and diverse, rich in nuts, seeds, fruits, vegetables, whole grains, and legumes. The primary fat source is olive oil (usually extra virgin), with a moderate intake of fish, poultry, dairy, eggs, and alcohol and rare consumption of meats, sweets, and processed foods.
The study evaluated the long-term benefits of adhering to a Mediterranean diet among participants of the Women’s Health Study and explored the biological mechanisms behind the diet’s health effects. Investigators assessed approximately 40 biomarkers representing various biological pathways and clinical risk factors.
Biomarkers of metabolism and inflammation were the most significant contributors, followed by triglyceride-rich lipoproteins, adiposity, and insulin resistance. Other pathways related to branched-chain amino acids, high-density lipoproteins, low-density lipoproteins, glycaemic measures, and hypertension had smaller contributions.
Even modest changes in established risk factors for metabolic diseases—particularly those linked to small molecule metabolites, inflammation, triglyceride-rich lipoproteins, obesity, and insulin resistance—can yield substantial long-term benefits from a Mediterranean diet. This finding underscores the potential of encouraging healthier dietary habits to reduce the overall risk of mortality.
The study identifies important biological pathways that may help explain the reduced all-cause mortality risk. However, the authors note key limitations, such as the study being limited to middle-aged and older well-educated female health professionals who were predominantly non-Hispanic and white. Additionally, the study relied on food-frequency questionnaires and other self-reported measures like height, weight, and blood pressure. Despite these limitations, the study’s large scale and long follow-up period are strengths.
Medical professionals already recognise the health benefits of the Mediterranean diet. This study offers insights into why the diet may be so beneficial. The researchers conclude that public health policies should promote the healthful dietary attributes of the Mediterranean diet and discourage unhealthy adaptations.
Source: Brigham and Women’s Hospital
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