Mediterranean Diet Lowers CVD Risk in Prospective Study

Nicola M. Parry, DVM

September 29, 2016

Increased adherence to a Mediterranean diet was associated with decreased cardiovascular disease (CVD) incidence and mortality, according to a prospective study published online September 29 in BMC Medicine.

Among healthy individuals with greater adherence to a Mediterranean diet, the risk for incident CVD was 5% to 15% lower than in individuals with poor adherence.

"Our study is the first report on the association of predefined Mediterranean diet adherence with CVD in a UK general population setting," write Tammy Y. N. Tong, from the Medical Research Council Epidemiology Unit, University of Cambridge School of Clinical Medicine, United Kingdom, and colleagues. "In this UK cohort, overall, we observed an inverse association of adherence to the Mediterranean diet with incident CVD and all-cause mortality."

"We estimate that 3.9% of all new [CVD] cases or 12.5% of cardiovascular deaths in our UK-based study population could potentially be avoided if this population increased their adherence to the Mediterranean diet," Nita Forouhi, MRCP, PhD, senior author from the Medical Research Council Epidemiology Unit at the University of Cambridge, United Kingdom, said in a journal news release.

The Mediterranean diet is rich in fruits, vegetables, legumes, cereals, and olive oil, and low in red meats. It also contains moderate amounts of fish and dairy products.

In the United Kingdom, the UK National Institute for Health and Care Excellence recommends a Mediterranean diet for secondary prevention of CVD. However, the association of the Mediterranean diet with the primary prevention of CVD in the UK has remained unknown.

Tong and colleagues therefore conducted a study to investigate the association of a Mediterranean diet with new-onset CVD, CVD mortality, and all-cause mortality in a UK-based cohort. They also aimed to estimate the population-attributable fraction for CVD and mortality outcomes among adults with low adherence to a Mediterranean diet.

The study included 23,902 initially healthy participants in eastern England who were involved in the European Prospective Investigation of Cancer (EPIC)-Norfolk cohort study. The researchers evaluated the participants' diets at baseline (1993 - 1997) and during follow-up (1998 - 2000), using food frequency questionnaires.

They defined the Mediterranean diet using a 15-point Mediterranean Diet Score (MDS) based on guideline recommendations from a Mediterranean dietary pyramid recently proposed by the Mediterranean Diet Foundation. They also evaluated three other MDSs that were based on different, preexisting algorithms.

According to the authors, 7606 of the 23,902 participants developed incident CVD events (nonfatal or fatal) over the course of 269,935 person-years (average follow-up, 12.2 years). In addition, 5660 participants died during 382,765 person-years (average follow-up, 17.0 years), and 1714 of these deaths were caused by CVD.

Although all four MDSs produced similar findings, the MDS based on the Mediterranean dietary pyramid had the strongest associations with CVD outcomes

Increased adherence to a Mediterranean diet was significantly associated with a 5% decreased incidence of CVD (hazard ratio [HR], 0.95; 95% confidence interval [CI], 0.92 - 0.97), a 9% decrease for CVD mortality (HR, 0.91; 95% CI, 0.87 - 0.96), a 6% reduction in incident ischemic heart disease (HR, 0.94; 95% CI, 0.90 - 0.98), and a 5% reduction in all-cause mortality (HR, 0.95; 95% CI, 0.93 - 0.98).

Moreover, the magnitude of benefit increased in a dose-dependent manner, such that those with moderate adherence had a 5% (HR, 0.95; 95% CI, 0.90 - 1.00) reduction in risk for incident CVD, and those with a high adherence had a 15% reduction (HR, 0.85; 95% CI, 0.80 - 0.90; P < .001 for trend).

In the EPIC-Norfolk population, the authors also estimated that 3.9% (95% CI, 1.3% - 6.5%) of total CVD could be attributed to poor adherence to a Mediterranean diet (equivalent to 9.7 cases of total CVD preventable per 1000 population over the course of 10 years). Similarly, the population-attributable fraction estimate for new-onset ischemic heart disease or stroke was 8.5% (95% CI, 3.1% - 13.9%), equivalent to 10.2 ischemic heart disease or stroke cases preventable per 1000 population); for CVD mortality and all-cause mortality, population-attributable fractions were 12.5% (95% CI, 4.5% - 20.6%) and 5.4% (95% CI, 1.3% - 9.5%), equivalent to 5.5 and 7.5 cases, respectively, per 1000 population.

The results of this study add to the mounting evidence about the health benefits of a Mediterranean-type diet, Tong and colleagues say, even in a non-Mediterranean country in which an optimal dietary pattern remains unknown.

"The findings indicate that adherence to the Mediterranean diet may contribute to a strategy for the primary prevention of CVD in the UK," they conclude.

This study was supported by grants from the Medical Research Council and Cancer Research UK. The authors have declared no relevant financial conflicts of interest.

BMC Med. Published online September 29, 2016. Full text

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