The health benefits of antioxidant-rich chocolate have received much recognition in recent years, with positive findings from a number of studies impacting on consumer awareness.
The majority of studies to date using flavonoid-rich cocoa have focussed on potential benefits for cardiovascular health, while a small number of studies have reported benefits for diabetes and skin health.
The new review, by Karen Cooper and colleagues from the Nestlé Research Center, in collaboration with researchers from the Medical University of South Carolina and University of California, Davis, draws together the current science reporting the health benefits of cocoa and chocolate consumption.
Published online in the British Journal of Nutrition , the review is a timely summary of the state-of-play for an ingredient that could be seen by food makers as a way to tap into consumers' desire to indulge their sweet tooth and benefit their health.
The reviewers point out that we have yet to determine exactly how much chocolate and what type is necessary to obtain potential health benefits.
"High quality research and well-planned human intervention trials are essential for furthering our scientific knowledge of polyphenols and health," said Gary Williamson, from Nestle Research Center and Functional Foods Chair at the University of Leeds.
These trials should focus on five areas, said the reviewers, with answers needed for questions about the underlying mechanism, the identity and bioavailability of active compounds, determination of relevant doses, and whether benefits are observed in populations with chronic disease.
Indeed, of the 28 human trials reviewed, 21 were in populations of apparently healthy individuals.
"To obtain results in a reasonable time frame and with the most likelihood of a significant result, we suggest targeting future trials to populations that are under antioxidant stress or deficiency due to a poor diet, chronic disease, ageing or have an elevated risk of CVD for other reasons," wrote the reviewers.
"Only with such results will it be possible to assess definitively whether or not cocoa and chocolate, which was originally only a decadent indulgence, can affect public health."
Previous studies have also identified that about 40 grams per day of chocolate as a relevant amount to infer benefits, but this needs confirmation from additional studies.
"In addition, the composition of the cocoa or chocolate must be carefully defined with regard to the proportions of polyphenols in the monomeric, oligomeric and polymeric forms, as well as the concentrations of the fats, sugars and other components such as proteins from milk solids," wrote Cooper et al.
"Further studies on milk chocolate to settle the bioavailability debate are most definitely required," they added.
The field of cocoa research has been and continues to be dominated by industry, with Mars, Barry Callebaut, Natraceutical and others joining Nestlé in funding studies into the potential health benefits of cocoa and chocolate.
This has led to some questioning if research bias may be evident in the literature.
"The main point to consider is that all the papers described here were published in peer-reviewed journals and therefore must be considered trustworthy and reliable; otherwise there is a need to investigate the integrity of the review process," wrote the reviewers.
"One way for industry (and academia) to improve transparency of ongoing human trials would be to formally register with one of the public domain agencies, such as with the National Institutes of Health, at the beginning of any study.
The advantage is that a null or negative study would still be public knowledge, and this could help bring more balance to this area of research," they added.
In a release from Nestlé Research Center, Cooper stated that the reviewers would use the recommendations to continue research into cocoa and health, "ensuring relevance to a balanced, healthy diet and active lifestyle".
Source: British Journal of Nutrition Published on-line ahead of print, Forthcoming Article, doi: 10.1017/S0007114507795296 "Cocoa and health: a decade of research" Authors: Karen A. Cooper, J.L. Donovan, A.L. Waterhouse and G. Williamson