A high adherence to the Mediterranean diet can reduce the mortality risk

Many large-scale observational epidemiological studies with a long follow up period of their participants support a reduced all-cause mortality risk among those who adhere more strongly to the Mediterranean Diet (Med Diet).

The precise mechanism through which increased adherence to the Med Diet helps individuals to reduce cholesterol, blood pressure and their risk of cardiovascular disease, as well as to manage their blood glucose levels and prevent type 2 diabetes is poorly understood.

This is what US researchers from Harvard University wanted to find out with the data from the Women’s Health Study, where tens of thousands of female health professionals who were at least 45 years old were enrolled. The women joined the study in the mid-1990s and answered a questionnaire with 131 questions about the foods they ate. Based on their answers, they received a score between 0 and 9. The higher the score, the higher their adherence the Med Diet.  For example, if they were above the median with the consumption of vegetables, fruit, nuts, whole grains, legumes or fish, they received one point. If the women were below the median for consumption of red and processed meats, they scored another point. Drinking between 5 and 15 grams of alcohol per day – which is the equivalent of a glass of wine or a can of beer – they scored one point as well.

Those with total scores between:

• 0 and 3 three were categorised as “low” adherence to the Med Diet
• 4 and 5: as “intermediate”,
• a total between 6 and 9 was considered as “high” adherence.

Even though the Women’s Health Study ended in 2004, the researchers followed up with the participants once a year for 25 years. The current study included 25,315 women where the dietary data and many biomedical measurements when they entered the study were available. By November 2023, 3,879 of the participating women had died.

The results showed that in this group of initially healthy US women after 25 years of follow- up, a higher adherence to the Med Diet was associated with a 23% lower risk of dying from any cause compared to those in the low adherence group. Among the many biomarkers examined, the risk reduction was partially explained by a group of cardiometabolic risk factors such as the biomarkers related to metabolism (eg. the amino acid alanine, a source of energy for muscles and the central nervous system), inflammation, insulin resistance and body mass index (BMI) and to a much lesser extent by blood pressure, HDL and LDL cholesterol. The researchers concluded that despite these results, most of the potential benefits of a high adherence to the Med Diet still remain unexplained.