Bittersweet result for dark chocolate

Studies show that polyphenol-rich dark chocolate has health benefits for overweight females

Studies show that polyphenol-rich dark chocolate has health benefits for overweight females

UK scientists have clinically proven that consuming polyphenol-rich dark chocolate has health benefits for overweight and obese females, whilst showing adverse effects for polyphenol-deficient chocolate.

Evidence already shows that polyphenol-rich dark chocolate can benefit blood pressure and glucose levels in healthy people, thanks to dark chocolate's antioxidant properties. Fewer studies have examined the involvement of the endocrine system – glands that secrete hormones – in mediating the cardiometabolic health-effects of polyphenols, until now.

Suzana Almoosawi from Queen Margaret University, Edinburgh, and her colleagues, applied these findings to a group of healthy women with a range of body mass indexes (BMIs). Obesity is often linked to numerous chronic diseases, such as hypertension and type 2 diabetes, so the team were keen to study the metabolic effects observed for different concentrations of polyphenols in dark chocolate, across a range of BMIs.

BMI is a number calculated using a person’s weight and height, which provides an indication of body fat. In this study, the group consisted of normal (19–25kg/m2), overweight (>25kg/m2) and obese (>30kg/m2) women. The single-blind, randomised study involved the consumption of polyphenol-rich dark chocolate (500mg of polyphenols), or a polyphenol-deficient dark chocolate placebo, over a four week period. ‘The placebo matched the polyphenol-rich dark chocolate for taste, texture, colour and macronutrient composition, but contained no polyphenols,’ explains Almoosawi.

On examining the metabolic effects on each female, the team found that the polyphenol-deficient placebo had an adverse effect on insulin sensitivity, antioxidant status, glucose levels and blood pressure. ‘Of note is that beneficial effects on metabolic endpoints were most readily observed in subjects with a BMI over 25,’ says Francisco Villarreal, an expert in cardiac mechanics from the University of California-San Diego, US. ‘This suggests that polyphenol-rich dark chocolate is helping to counter the effects of a high BMI, and in this manner potentially reducing cardiometabolic risks,’ he adds.

‘We hope that the findings from this research will encourage the industry to consider making polyphenol-rich chocolate available on the market,’ says Almoosawi. ‘However, we are still faced by many challenges. We still don’t know the implications of consuming large amounts of polyphenols and whether there could be adverse effects associated with long-term consumption.The health benefits of consuming polyphenol-rich dark chocolate should still be carefully balanced against any long-term adverse effects.’



  1. S Almoosawi et al, Food Funct., 2012, DOI: 10.1039/c2fo30060e

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