Diet and the heart
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I will discuss two recent articles which deal with diet and cardiovascular disease. Both have appeared in recent issues of the New England Journal of Medicine in this year of 2013. The first of these dealt with the prevention of cardiovascular disease with a Mediterranean diet. The traditional Mediterranean diet has a high intake of olive oil, fruits and nuts, vegetables and cereals with a moderate intake of fish and poultry and a low intake of dairy products and red meat. The dieters consumed wine with meals but in moderation. This was a randomized trial which actually was begun in October 2003. The primary endpoint of the trial was a composite of myocardial infarction, stroke, and deaths from cardiovascular causes. The initial sample involved 9000 participants. Participants were followed for a median of 4.8 years. The results showed a 30% reduction in the primary endpoints for those on the Mediterranean diets in comparison to the control group. The diet with supplemented extra-virgin olive oil or nuts resulted in the greatest reduction in the risk of major cardiovascular events among high-risk persons. The authors speculate that there may be a synergy between different aspects of the diet which decrease inflammation and endothelial dysfunction which led to the improved outcome. The 30% reduction is a large amount for just dietary intervention and exceeds many if not most drug interventions.
The second study presented a novel idea, namely, that possibly there is a mechanistic link between intestinal microbial metabolism and the risk of cardiovascular events in humans. Previous studies in animals had revealed such a link and this study confirmed it with human volunteers. It turns out that the microbes when they metabolize the choline moiety of lecithin which is found in various dairy and meat products produces a metabolite which is known as TMAO. The researchers quantified both plasma and urinary levels of TMAO and plasma choline after the lecithin challenge of two hard-boiled eggs where the lecithin had been labeled with deuterium. They did this before and after suppression intestinal microbes by antibiotic therapy. They also looked at the relationship between fasting TMAO and the incidence of major cardiovascular events. This trial was for three years with 4007 patients undergoing elective coronary angiography. Plasma levels of TMAO were markedly suppressed after the administration of antibiotics and then reappeared after the withdrawal of antibiotics. Increase plasma levels of TMAO were associated with an increased risk of major adverse cardiovascular events with the highest group having up to threefold increased risk. An elevated TMAO level predicted an increased risk of major adverse cardiovascular events after adjustment for traditional risk factors. Thus if further confirmed eggs and meat, mediated by gut bacteria, can increase cardiovascular risk independent of cholesterol content. The study is quite amazing in that we see the importance of the microbial flora and its interaction with food groups. Consequently a whole new realm of understanding nutrition may be about to flourish.
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