Dr Rutai Hui of the Chinese Academy of Medical Sciences and Peking Union Medical College in Beijing and colleagues, whose findings were published in the American Journal of Clinical Nutrition, concluded that there was no dose-effect relation or any effect in healthy participants.
“The results suggested that short-term of cocoa consumption reduced blood cholesterol, and this effect was more evident in studies with low dose cocoa supplementation and in subjects with cardiovascular risks,” said the team.
They maintain though that eating moderate amounts of chocolate could be a worthwhile dietary approach for preventing high cholesterol in certain people, but that more research is needed to determine the efficiency of eating moderate amounts of cocoa on lipid profile in long-term intervention and in subjects with other cardio metabolic risk factors.
Cardiovascular disease (CVD) is one of the leading causes of morbidity, mortality, and disability in many parts of the world, especially in Western countries, and accounts for one-fifth of all mortality in the US, note the Chinese team.
The Chinese team noted that a substantial number of observational trials have reported that the supplementation of cocoa products affects lipid profiles in subjects with cardiovascular-related diseases as well as healthy individuals.
“Polyphenols have been shown to inhibit cholesterol absorption and biosynthesis and to promote the expression of LDL cholesterol receptors, while cocoa butter also contains approximately 33 per cent monounsaturated oleic acid, which has been shown to favour an ideal lipid profile,” said the authors
But the sample sizes of these studies are relatively small and the conclusions are inconsistent, determined the team, and as a result they decided to conduct a systemic review of the scientific literature and a meta-analysis of all published randomized controlled trials that investigated the effects of cocoa on blood cholesterol to determine.
The researchers searched the literature to find studies that looked at how cocoa affected blood fats and found eight trials including 215 people. Four trials investigated the effect of cocoa on healthy subjects, while the others examined the effect of chocolate consumption on patients with CVD risks such as hypertension or diabetes.
They said that in these trials, the main sources of cocoa were dark chocolate and cocoa powder, the doses of polyphenols in the studies ranged from 30 to 963 milligrams (mg) per day and the treatment duration varied from two to 18 weeks.
All of the trials were randomised, prospective and placebo controlled.
The team noted that participants with risk factors CVD saw their LDL cholesterol drop by around 8 mg/dL each but found that consumption of cocoa products did not affect blood cholesterol in the healthy cohort.
They further stated that their analysis demonstrated that only people who ate small amounts of cocoa derived products, an amount containing 260mg of polyphenols or less, experienced cholesterol lowering effects.
But the researchers said that they still did not know the optimal daily consumption of cocoa for improving lipid metabolism or vascular health and call for additional studies.
"Future research efforts should concentrate on higher-quality and more rigorous randomized trials with longer follow-ups to resolve the uncertainty regarding the clinical effectiveness," concluded Hui and his colleagues.
Meanwhile, a study in March, which was conducted by German researchers and published in the European Heart Journal (EHJ), found that small amounts of chocolate can lower blood pressure and reduce the risk of heart disease.
The authors of the EHJ study, which involved a cohort of they assessed 19,357 people aged between 35 and 65, said that they found that those who ate the most amount of chocolate – an average of 7.5 grams a day – had lower blood pressure and a 39 per cent lower risk of having a heart attack or stroke compared to those who ate the least amount – an average of 1.7 grams a day.
Source: American Journal of Clinical Nutrition
Published online ahead of print: doi: 10.3945/ajcn.2009.28202
Title: Short-term effect of cocoa product consumption on lipid profile: a meta-analysis of randomized controlled trials
Authors: L Jia, X Liu, Y Yi Bai, S Hua Li, K Sun, C He, and Ri Hui