Catechins, but not quercetin, behind some of cocoa & tea’s benefits

By Stephen DANIELLS

- Last updated on GMT

Catechins, but not quercetin, behind some of cocoa & tea’s benefits

Related tags: Insulin resistance, Clinical trial, Nutrition

Supplementation with epicatechin may beneficially affect insulin levels and insulin resistance, but another flavonoid quercetin had no effect, says a new study from The Netherlands.

Epicatechin is found in flavonoid-rich foods such as cocoa and tea, and has been linked to a range of health benefits, including cardiovascular health. Quercetin is a flavonoid found in fruits and vegetables, and data from in vitro​ or animal studies have also linked the compound to cardiovascular benefits. Data from human studies is rare, however.

Supplements of epicatechin or quercetin were found to produce different results in healthy men and women, with only epicatechin showing improvements in insulin levels and insulin resistance, according to findings published in the American Journal of Clinical Nutrition.

On the other hand, neither compound was found to have an effect on blood pressure, blood flow, or any other risk factors for cardiovascular disease, report researchers from the Top Institute Food and Nutrition, Wageningen University, and Unilever R&D Vlaardingen.

“Our findings suggest that epicatechin plays a role in the beneficial effects of cocoa and tea on insulin resistance,”​ they wrote. “No effects of epicatechin were seen on endothelial function or other markers of cardiometabolic health. Quercetin, a major flavonol in tea, did not influence any of the markers of cardiometabolic health. It is unlikely, therefore, that quercetin plays a role in the cardioprotective effects of tea.”

Study details

The researchers, led by Peter Hollman from Wageningen University, recruited 37 healthy men and women with an average of 66 and an average BMI of 26.7 kg/m2 to participate in their randomized, double-blind, placebo-controlled crossover trial. Participants were randomly assigned to receive placebo, 100 mg per day of (−)-epicatechin, or 160 mg per day of quercetin-3-glucoside for four weeks. Each intervention was followed by four week ‘washout’ period before crossing over to another intervention.

Results showed that epicatechin affected insulin levels and insulin resistance, measured using the homeostasis model (HOMA-IR).

“Epidemiologic studies have shown an association between HOMA-IR and CVD risk,” ​explained the researchers. “In our study, the reduction in mean HOMA-IR of -0.38 following epicatechin supplementation was smaller than that of the cocoa meta-analysis ​[Hooper et al. Am J Clin Nutr​ 2012, Vol. 95, pp. 740-51].

“Our study population had a mean HOMA-IR of 1.57, which is below the threshold of insulin resistance. The response to epicatechin may be stronger in subjects with impaired fasting glucose concentrations and higher levels of insulin resistance. The results of the present study suggest that epicatechin contributes to the favorable effects seen in cocoa trials.”

No effects were observed on insulin measures for quercetin, while neither compound resulted in changes to other measures of cardiovascular health.

Source: American Journal of Clinical Nutrition
Published online ahead of print, doi: 10.3945/ajcn.114.098590
“Effects of the pure flavonoids epicatechin and quercetin on vascular function and cardiometabolic health: a randomized double-blind, placebo-controlled, crossover trial”
Authors: J.I. Dower, J.M. Geleijnse, L. Gijsbers, et al. 

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