Researchers at Brigham and Women’s Hospital have identified and evaluated underlying mechanisms that may explain the 23 percent reduction in all-cause mortality risk for American women with Mediterranean diet.
The research results are published on JAMA.
The health benefits of the Mediterranean diet
The health benefits of the Mediterranean diet have been reported in numerous studies, but there is limited long-term data on its effects in U.S. women and little understanding of 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 a higher intake of the Mediterranean diet had up to a 23 percent lower risk. of mortality from all causes, with benefits for both cancer mortality and cardiovascular mortality.
The researchers found evidence of biological changes that could help explain why: They detected changes in biomarkers of metabolism, inflammation, insulin resistance, and more.
“For women who want to live longer, our study says to pay attention to your diet. The good news is that following a Mediterranean dietary pattern could lead to a reduction of about a quarter in the risk of death for more than 25 years, with benefits for both cancer and cardiovascular mortality.”
Leading causes of death among women (and men) in the United States and globally,” said senior author Samia Mora, MD, a cardiologist and director of the Center for Lipid Metabolomics at the Brigham.
The Mediterranean diet is a diversified plant-based diet, rich in plants (nuts, seeds, fruits, vegetables, whole grains, legumes). The main fat is olive oil (usually extra virgin) and the diet also includes moderate consumption of fish, poultry, dairy products, eggs and alcohol and infrequent consumption of meat, sweets and processed foods.
The present study examined the long-term benefits of adhering to a Mediterranean diet in a U.S. population recruited as part of the Women’s Health Study and explored biological mechanisms that may explain the health benefits of the diet. Study investigators evaluated a panel of approximately 40 biomarkers representing various biological pathways and clinical risk factors.
Biomarkers of metabolism and inflammation made the greatest contribution, followed by triglyceride-rich lipoproteins, adiposity, and insulin resistance.
Other biological pathways related to branched-chain amino acids, high-density lipoprotein, low-density lipoprotein, glycemic measures, and hypertension make minor contributions.
“Our research provides significant public health insights: 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 produce substantial long-term benefits from following a Mediterranean diet, this finding highlights the potential to encourage healthier eating habits to reduce overall mortality risk,” said lead author Shafqat Ahmad, Ph.D., associate professor of Epidemiology at from Uppsala University in Sweden and a researcher in the Center for Lipid Metabolomics and Division of Preventive Medicine at the Brigham.
The present study identifies important biological pathways that may help explain the risk of all-cause mortality. However, the authors note some key limitations, including that the study was limited to middle-aged and older, well-educated, predominantly non-Hispanic, and white female healthcare professionals.
The study relied on food frequency questionnaires and other self-reported measures, such as height, weight and blood pressure. But the study’s strengths include 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 could modify its influence on health.
“The health benefits of the Mediterranean diet are recognized by medical professionals, and our study offers insights into why the diet may be so beneficial. Public health policies should promote the healthful dietary attributes of the Mediterranean diet and should discourage unhealthy adaptations,” Mora said.
Mediterranean diet and lower cardiovascular risk
A study by researchers at Brigham and Women’s Hospital, Harvard Medical School, and the Harvard TH Chan School of Public Health offers insights from a cohort study of women in the United States who reported consuming a Mediterranean-style diet.
Researchers found a 25% reduction in cardiovascular disease risk among study participants who consumed a diet high in plants and olive oil and low in meat and sweets. The team also explored why and how a Mediterranean diet might mitigate the risk of heart disease and stroke by examining a panel of 40 biomarkers, which represent new and established biological drivers of heart disease. The team’s findings are published on JAMA Network Open .
Our study conveys a strong public health message that modest changes in known cardiovascular disease risk factors, particularly those related to inflammation, glucose metabolism, and insulin resistance, contribute to the long-term benefit of a Mediterranean diet on the risk of cardiovascular diseases. This understanding may have important downstream consequences for the primary prevention of cardiovascular disease,” said lead author Shafqat Ahmad, Ph.D., a research scientist at the Brigham and Harvard Chan School.
Randomized trials conducted in Mediterranean countries and observational studies have previously linked the Mediterranean diet to reductions in cardiovascular disease, but the underlying mechanisms are unclear. The current research is based on data from more than 25,000 health professionals who participated in the Women’s Health Study.
Participants completed dietary food intake questionnaires, provided blood samples to measure biomarkers, and were followed for up to 12 years. The primary outcomes analyzed in the study were the incidence of cardiovascular disease, defined as first events of heart attack, stroke, coronary artery revascularization, and cardiovascular death. The team classified study participants based on low Mediterranean diet consumption, medium or higher.
They found that 428 (4.2%) of women in the low group had a cardiovascular event compared to 356 (3.8%) in the medium group and 246 (3.8%) in the high group, representing a reduction in relative risk by 23% and 28% respectively, a benefit of similar magnitude to that of statins or other preventive drugs.
The team observed changes in inflammation signals (accounting for 29% of the cardiovascular disease risk reduction), glucose metabolism and insulin resistance (27.9%), and maximum body index (27.3 %). The team also found links to blood pressure, various forms of cholesterol, branched-chain amino acids and other biomarkers, but found that these accounted for less of the association between the Mediterranean diet and risk reduction.
“While previous studies have demonstrated benefits for the Mediterranean diet in reducing cardiovascular events and improving cardiovascular risk factors, this was a black box regarding the extent to which improvements in known and new risk factors contribute to these effects,” said corresponding author Samia Mora. , MD, MHS, cardiovascular medicine specialist at Brigham and Harvard Medical School. “In this large study, we found that modest differences in biomarkers contributed multifactorial to this observed long-term cardiovascular benefit.”
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