Mediterranean diet lowers risk of multiple heart and metabolic diseases

Study reveals that the Mediterranean diet not only prevents the first cardiometabolic disease but also reduces the risk of developing multiple diseases, particularly for non-manual workers.

In a recent study published in The Journal of Nutrition, researchers explored the relationships between adherence to the Mediterranean diet and the risk of developing two or more cardiometabolic diseases.

Their findings indicate that following the Mediterranean diet may reduce the risk of developing a second cardiometabolic disease, particularly over shorter follow-up periods, with this effect varying by social class. The study found significant protective effects in the 10- and 15-year follow-up periods, with hazard ratios of 0.67 and 0.80, respectively. However, over longer follow-up durations, the impact was diminished.

Background

As the global population ages and lifespans increase, many people experience multiple co-occurring diseases, termed multimorbidity, which negatively affects an individual’s well-being and places pressure on healthcare systems. Cardiometabolic diseases (CMD), which include type 2 diabetes, stroke, and heart attacks, share drivers and often occur together, forming cardiometabolic multimorbidity (CMM). In the United Kingdom, CMM affects between 3% and 6% of the population and significantly reduces life expectancy by up to 15 years for people who are 60 years old.

Unhealthy diet is an important risk factor for CMD. The Mediterranean diet, rich in olive oil, fish, and plant-based foods, has been linked to a lower risk of CMD. Studies have also shown that higher adherence is linked to lower risk of diabetes, stroke, and heart disease. However, while the diet decreases the risk of developing a first CMD, its effect on the transition to multiple CMDs or CMM is not well understood.

About the study

The protective effect of the Mediterranean diet was more pronounced in transitions from first myocardial infarction (MI) and type 2 diabetes (T2D) to cardiometabolic multimorbidity during 10- and 15-year follow-ups, while its impact on stroke-related transitions was less significant.

In this study, researchers focused on how the Mediterranean diet influences the progression from being free of CMD to developing the first CMD and then to CMM across various follow-up durations. The study utilized two different Mediterranean diet scores: the median-based Mediterranean diet score (m-MDS), which assigns scores based on cohort-specific medians, and the pyramid-based Mediterranean diet score (pyr-MDS), which accounts for both traditional Mediterranean diets and contemporary food environments. The pyr-MDS was found to be a stronger predictor of disease risk, particularly in shorter follow-up periods.

The data was from a large study in the United Kingdom that recruited more than 30,000 people between 40 and 79 starting in 1993. When the study began, the participants completed questionnaires related to food, lifestyle, and health and were followed until 2018. The analysis excluded people who had CMDs at the start of the study, resulting in a sample of 21,900 participants.

Researchers measured diet adherence through the m-MDS and pyr-MDS diet scores, and dietary intakes were adjusted for a 2000 kcal per day diet to account for differences in quantity. The participants were tracked for CMD events and death from baseline to 2018 using hospital records and death certificates, with CMM recorded at the point that they developed a second CMD.

Other factors that were recorded included family history of CMD, medication use, education, marital status, social class, physical activity, smoking, body mass index (BMI), sex, and age.

To analyze the data, researchers grouped the participants based on adherence to the diet, testing for differences in characteristics at baseline. After adjusting for other factors, they then estimated the relationship between each of the diet scores and CMM risk.

Findings

Adherence to the Mediterranean diet was linked to significant reductions in first cardiometabolic disease (CMD) risk even over a long follow-up period (21.4 years), highlighting the diet’s long-term health benefits beyond its effects on multimorbidity.

The 21,900 participants initially free from CMD were followed for a median of 21.4 years, during which time 5,028 developed at least one CMD, while 734 progressed to CMM.

People who adhered more closely to the diet were also more likely to be younger, non-smokers, better educated, have higher levels of physical activity, and take drugs to lower lipid levels. Additionally, the study found that adherence to the Mediterranean diet reduced the risk of transitioning from being CMD-free to developing a CMD, with hazard ratios of 0.94 over 10 years, 0.92 over 15 years, and 0.93 over the entire follow-up period.

The pyramid-based MDS showed stronger associations for the transition to CMM in shorter follow-up periods, with hazard ratios of 0.67 over 10 years and 0.80 over 15 years. Higher Mediterranean diet scores were correlated with lower rates of CMM, and having a higher diet score at baseline was linked to a lower risk of developing CMM during follow-ups.

The study also highlighted significant differences in the impact of the diet between manual and non-manual workers. For non-manual workers, adherence to the Mediterranean diet was associated with a reduced risk of transitioning from CMD to CMM, while for manual workers, no significant effect was observed. Social class was a significant modifier of the diet's impact on CMM risk. This could be due to differences in socioeconomic factors like healthcare access, food selection, and diet quality. Manual workers may prioritize food price over nutritional value, potentially consuming a lower variety of nutrient-rich foods, which could explain the weakened effect of the Mediterranean diet in this group.

Conclusions

The study investigated how following the Mediterranean diet affects the onset of CMM in the United Kingdom population across different follow-up durations, uncovering potential links between diet adherence and lower risk of CMM in shorter periods. Previous studies in the UK and China have linked diet to the development of a first CMD, but none have examined the transition to CMM. The use of two different Mediterranean diet scores in this study—m-MDS and pyr-MDS—allowed for a more nuanced understanding of diet quality, with the pyr-MDS showing stronger associations in the shorter follow-up periods.

The strengths of this study include the large cohort size, long follow-up periods, and use of more than one diet score to measure adherence. However, diet was measured only once at baseline, and the analysis could not account for changes. The participants were predominantly European, limiting generalizability.