By Henry R. Black, MD Nov 14, 2012. Clinical Professor of Internal Medicine at the New York University School of Medicine, a member of the Center for the Prevention of Cardiovascular Disease, and former President of the American Society of Hypertension.
We have been searching for a long time for some nutritional additive or diet, or some approach to nutrition, that seems to reduce cardiovascular disease, coronary disease, and strokes especially, and so far [the search] has been pretty disappointing. We have not found anything that really works and, what is worse, even if you found a diet that would work, such as the DASH diet, it is very hard to comply with it over the long term.
An interesting new player in this effort is chocolate, dark chocolate in particular, flavanol-enriched chocolate. The [evidence on chocolate] first came from animal studies that showed improvement in forearm vasodilation, an indicator of endothelial function and nitric oxide availability. Recently, 2 more studies have shed more light on this factor.
One study included patients with class II heart failure, primarily with ejection fractions less than 50%, not those with preserved systolic function. [1] This study from Europe randomly assigned participants to receive what they call flavanols-enriched chocolate or dark chocolate vs white chocolate, which did not contain these flavanols. They found that, in the short term, 2 hours after ingestion, those who ate the dark chocolate had improvements in forearm vasodilation which was not seen in patients who ate the white chocolate. They then gave the participants chocolate bars to eat over the next 4 weeks and repeated these studies, with similar results.
What does that mean to us? Does it mean that we should start eating chocolate? Does it mean that we should prefer dark chocolate instead of milk chocolate or white chocolate? Perhaps. If we are going to recommend eating chocolate, we would like to be sure that we get the right kind of chocolate. I have looked at food labels recently and cannot tell what kind of chocolate is contained in dark vs milk or white chocolate. But if I am going to indulge [in chocolate], that might be something to know. Of interest, the participants did not gain weight during this 4-week period, and also there were some issues of reduced insulin sensitivity, which was a bit of a surprise.
The other study looked at people who were young and healthy who were randomly assigned to eat dark chocolate or white chocolate and then underwent a glucose tolerance test. [2] The investigators were testing for an increase in glucose or glucose toxicity and whether that could be prevented by dark chocolate. In fact it could. Those who ate the white chocolate had a reduction in forearm vasodilation that was not seen in people who ate the dark chocolate. Dark chocolate did not improve forearm vasodilation during a glucose tolerance test, but these were young men for the most part — about 28 years of age — [and it would have been very difficult to demonstrate improvement]. It’s a little hard to extrapolate that to some of us older people who might like chocolate, but it is interesting that the glucose toxicity that we sometimes see might be prevented if dark chocolate’s part of your plan.
Finally, my colleague Franz Messerli [3] wrote a recent article about Nobel laureates and chocolate consumption per country. He found that the more chocolate eaten by people in those countries, the higher number of Nobel laureates. This is a bit tongue-in-cheek and I want to congratulate the New England Journal of Medicine for having a sense of humor. But several things are missing from this analysis. Many people who win Nobel prizes win it for work they did in their teens and twenties. Your chocolate intake probably is not all that high then.
It is possible that there’s something here that we actually like to do. We have to make sure that we watch the calories, that we don’t gain too much weight, because I think we’re pretty sure that eating too much isn’t good for you either.
References
1.Flammer AJ, Sudano I, Wolfrum M, et al. Cardiovascular effects of flavanol-rich chocolate in patients with heart failure. Eur Heart J. 2012;33:2172-2180.
2.Grassi D, Desideri G, Necozione S, et al. Protective effects of flavanol-rich dark chocolate on endothelial function and wave reflection during acute hyperglycemia. Hypertension. 2012;60:827-832. 3.Messerli FH. Chocolate consumption, cognitive function, and Nobel laureates. N Engl J Med. 2012;367:1562-1564.
