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Sweet! Chocolate for Mind AND Body
Abstract & Commentary
By Russell H. Greenfield, MD
Synopsis: The study authors reviewed observational data on chocolate consumption and the risk of cardiometabolic disease, and found strong evidence of a protective effect. The wide variety of methods employed across studies, among other issues, make cause and effect assumptions premature, though they do fall in line with previous data suggesting chocolate's health benefits.
Source: Buitrago-Lopez A, et al. Chocolate consumption and cardiometabolic disorders: Systematic review and meta-analysis. BMJ 2011;343:d4488.
Chocolate has, of course, long been a favored food around the globe. In recent years, data suggesting chocolate might also offer health benefits has been greeted with smiles, but in the recesses of many people's minds was the lingering concern that the high fat and sugar content of chocolate, in general, might in the long run do more harm than good. In this systematic review and meta-analysis, researchers sought to examine and better define the relationship between chocolate consumption and subsequent risk of cardiometabolic disorders (including cardiovascular disease, diabetes, and metabolic syndrome) in adults.
Medline, Embase, Cochrane Library, PubMed, CIN- AHL, IPA, Web of Science, Scopus, Pascal, and reference lists of relevant studies were scoured for randomized controlled trials, cohort, case-control, and cross-sectional studies where the level of chocolate consumption was related to the development of cardiometabolic disorders. There was no language restriction, and interpreters were available if translation were necessary.
Reviewers worked in pairs and initially screened the titles and abstracts, with disagreements resolved through consensus or consultation with a third reviewer. Full text articles were retrieved for the selected titles. Reference lists of the retrieved articles were searched for additional publications, and authors of the retrieved papers contacted directly for any unpublished data. The retrieved studies were assessed again by two independent authors to ensure that they satisfied inclusion criteria. Extracted data included participant characteristics, type of intervention and measurement methods, and reported outcomes. For each study, the group with highest chocolate consumption was compared to the group with the lowest consumption, and summary relative risks were calculated. Results were pooled using a random effects model. Testing for publication bias and heterogeneity was performed.
Out of the 4576 references initially considered, full text assessment of 53 articles was undertaken, and a total of seven articles (one cross-sectional study, six cohort studies), including data on more than 100,000 subjects, were considered appropriate for analysis. Many of the excluded studies did not report on levels of chocolate consumption or on outcomes relevant to the meta-analysis. The studies analyzed had no industry funding, and were deemed of adequate quality without evident bias.
Participants' ages ranged from 25-93 years, the vast majority of whom were Caucasian, and follow-up was from 8-16 years. Some studies included subjects taking prescription drugs. Although no study focused specifically on metabolic syndrome as an outcome, reported outcomes included heart attack, heart failure, diabetes and stroke, among others. One study used participant diaries of chocolate consumption to draw conclusions, while the other six employed food frequency questionnaires. Specific type (milk, dark, or white) of chocolate ingested was not reported, only overall chocolate consumption.
Five studies documented a significant inverse association between chocolate intake and development of cardiometabolic disorders after adjustment for numerous possible confounders, including coffee consumption and body mass index. With pooling of retrieved measures of association, high chocolate consumption was found to decrease the risk of cardiometabolic disorders by approximately one-third 37% for any cardiovascular disease (RR = 0.63, 95% CI 0.44 to 0.90) and 29% for stroke (RR = 0.71, 95% CI 0.52 to 0.98). No significant association was observed in relation to heart failure. One study reported on the association between chocolate consumption and diabetes, finding a beneficial effect for both Japanese men and women (HR = 0.65 [0.43 to 0.97] and 0.73 [0.48 to 1.13], respectively).
The authors conclude that on the basis of observational evidence, higher levels of chocolate consumption may be associated with a substantial lowering of the risk of cardiometabolic disease.
Chocolate often falls under the category of "guilty pleasure," but data such as those just described make this classification almost anachronistic, a perspective long held now largely being proved false. That's reason to smile on many fronts.
Cardiometabolic disorders are a major source of morbidity and mortality around the world, but they are also largely preventable through diet and lifestyle measures. One might have thought that part of such a prevention program would be avoidance of chocolate. Apparently, not so, and chocolate may even be considered part of a preventive strategy. Studies suggest that chocolate provides antioxidants, and anti-inflammatory and anti-thrombotic effects, among others, as a result of the polyphenols present (dark chocolate contains almost three times more catechins than tea) and the specific type of fat present in high percentage cocoa.
Of course, one must consider degree of consumption many of the products available on store shelves are extremely high in saturated fat (primarily milk fat) and sugar, and over-indulgence of the type not uncommonly seen in today's society may negate any potential health benefits, even when the discussion turns to the apparently healthier dark varieties (cocoa content > 70%).
The authors are appropriately cautious about their results due to a number of factors: the study was observational in nature, so firm conclusions about cause and effect cannot be supported; the data come from a small number of trials, more than half of which were published in the past two years; means of determining chocolate intake were inexact; there were no randomized controlled trials to review; the majority of subjects were white, so generalizability is hampered; and in light of significant heterogeneity between studies the authors felt they could not venture a clear dose-response relationship for chocolate intake and decreased risk of cardiometabolic disease.
Beyond the possible physical benefits of a small piece of high-quality chocolate each day are the emotional benefits chocolate has been found to acutely enhance mood in some trials. And then there is consideration of the developing world where, as the study authors point out, much of our chocolate comes from and where cardiometabolic disorders are increasing in prevalence. Their own natural resource could be a boon for public health, both locally and globally.
Yes, there are severe limitations to the conclusions that can be drawn from this study, but the results align with those of prior data and lend credence to the idea that chocolate (in moderation) is not a guilty pleasure it's the all-too-rare pleasure that is good for us.