LOS ANGELES – Chronic heart failure patients who ate a special superhigh-flavonol dark chocolate bar daily experienced favorable changes consistent with decreased vascular resistance and diminished left ventricular afterload in a randomized, double-blind, crossover pilot study.
"It should be emphasized that these patients were already on maximal tolerated guideline-indicated therapy. In terms of medical interventions, there weren’t many more things we could do. So I think that in addition to looking at new drugs, we need to look at evidence-based new diets to see if they can reduce morbidity and mortality in heart failure," Dr. Roger Corder said in presenting the chocolate study results at the annual scientific sessions of the American Heart Association.
The likely mechanism of benefit in heart failure patients involves a dark chocolate–induced reduction in endothelial dysfunction.
"Prior studies show consumption of cocoa flavonols in daily doses of 750 mg or more improve endothelial function in patients with coronary artery disease, in healthy subjects, and in diabetics," noted Dr. Corder of Queen Mary University of London.
The study involved 32 patients with stable heart failure on maximal medical therapy, all of whom had a history of ischemic heart disease. They were randomized to daily consumption of a 50-g bar of high-flavonol chocolate or a low-flavonol chocolate bar for 4 weeks, then crossed over to daily consumption of the other bar for another 4 weeks.
The test product contained 1,094 mg of flavonols per bar, while the low-flavonol comparator contained 95 mg. The high-flavonol chocolate bar was a custom-made product whose flavonol content far exceeds anything on the market. Dr. Corder and coinvestigators tested 50 brands of commercially available dark chocolate bars averaging 76% cocoa solids and determined their average flavonol content was 312 mg/50 g.
The study end points were change in diastolic blood pressure and N-terminal prohormone of brain natriuretic peptide (NT-proBNP) levels after 4 weeks of eating each type of chocolate bar.
Twenty-four patients completed the study. Mean NT-proBNP dropped by an average of 39% from a baseline of 200 pmol/L after 4 weeks of eating the high-flavonol chocolate.
"Given that other trials of medications, including angiotensin receptor blockers, have shown a 30% reduction in NT-proBNP is associated with improved clinical outcomes, this looks to us like something of interest to pursue further with additional clinical studies. It’s worth noting that 12 of the 24 patients had a drop in NT-proBNP of 30% or more," Dr. Corder said.
From a baseline blood pressure of 126/71 mm Hg, diastolic pressure fell by 5 mm Hg in conjunction with consumption of the high-flavonol bar. Systolic pressure did not change significantly. Maintenance of systolic blood pressure with a reduction in diastolic pressure implies an increase in cardiac output – "and that would really be the optimum thing to have happened," he continued.
The low-flavonol chocolate bar did not produce changes in blood pressure or NT-proBNP.
A couple of down sides with the experimental high-flavonol chocolate bar emerged during the study. One was taste. Three of the eight study dropouts quit because they found the product’s taste unacceptable, while the others left for reasons unrelated to the study.
"We had an issue with taste. Even the patients who finished the study didn’t like the taste. There may be other countries where dark chocolate is popular, but the East of London would rather have their sweet milk chocolate than dark chocolate," according to Dr. Corder.
Weight gain is another concern. Both chocolate bars contained about 19 g of fat, including 12 g of saturated fat, per 50-g serving, with about 260 calories. From a baseline body weight of 85.7 kg, participants gained roughly 0.3 kg over the course of 4 weeks.
"In terms of long-term therapy, it may not be suitable to take dark chocolate on a daily basis at this level," he said.
However, food scientists involved in the study are tweaking the recipe to improve the taste of the superhigh-flavonol bar. There is also the option of extracting the flavonols and placing them in some other nutraceutical food product.
The study was funded by Swiss chocolate giant Barry Callebaut. Dr. Corder reported receiving a significant research grant from the company.