Nutrients found in cocoa may improve the heart health of patients with advanced kidney disease, and perhaps anyone else at risk for heart disease, according to a new study.
Heart disease is the leading cause of death in patients who have a kidney condition called end-stage renal disease and who require dialysis. There are few effective treatment options to prevent heart failure other than a kidney transplant, according to the American Society of Nephrology.
In the new study, doctors in Germany looked at effects of two nutrients found in cocoa: catechin and epicatechin. These nutrients, thought to be heart-healthy, are part of a group of compounds called flavanols, and are also present in tea, wine and some vegetables.
The doctors concocted a brew with these flavanols and gave it to 26 patients with end-stage renal disease. The drink dramatically improved blood flow and lowered blood pressure in all of the patients within a month, according to the findings, published today (Dec. 17) in the Clinical Journal of the American Society of Nephrology (ASN).
A nearly identical placebo drink, that did not contain the catechin and epicatechin flavanols, had no effect on 26 similar patients in the control group. The study was double blinded, meaning neither the researchers nor the patients knew who had received the placebo drink and who had received the drink with the cocoa nutrients. [Science You Can Eat: 10 Things You Didn't Know About Food]
However, the researchers noted that although these compounds are found in cocoa beans, they are largely absent from processed chocolate.
The authors of an editorial accompanying the study in the journal wrote that otherwise effective heart medications, such as statins, have failed to improve the heart health of people with end-stage renal disease. "The burden of cardiovascular disease in dialysis patients is so devastating that a promising intervention like cocoa flavanols deserves full attention by the nephrology community," they wrote.
These authors, Drs. Carmine Zoccali and Francesca Mallamaci, both kidney specialists at Italy's National Research Council in Reggio di Calabria, concluded that the new findings, if confirmed by larger studies, may represent a turning point in care for these patients.
The kidney is a bean-shaped organ that filters blood, removing the waste products of metabolism and sending them to the bladder, where they are excreted through urine. Approximately 10 percent of adult Americans, or about 20 million people, have some form of kidney disease, according to the Centers for Disease Control and Prevention. Those with the most severe form of kidney disease, called stage 5 or end-stage, require either a kidney transplant or regularly dialysis (the mechanical filtering of the blood) to survive.
Diabetes and high blood pressure are the major risk factors for developing kidney disease. Poorly functioning kidneys leave too much waste in the blood stream, and this, in turn, can lead to a hardening of the arteries, higher blood pressure and, ultimately, heart failure.
Previous studies have demonstrated the heart-healthy benefits of cocoa, which has the highest concentrations of catechin and epicatechin among plant-based foods. The Europe-based Flaviola Health Study has found that cocoa flavanols can reduce artery stiffness, improve blood flow and lower blood pressure. Other studies have revealed modest, positive effects of these compounds for people who smoke or who have diabetes, cardiovascular disease or high blood pressure.
A previous study, led by Dr. Tienush Rassaf of the University Hospital Essen in Germany, was the first to test the benefits of cocoa on kidney disease patients. In that study, the researchers gave participants a low-sugar, fruit-flavored drink with few notable nutrients other than the cocoa flavanols. The beverage was made from a powder provided by Mars Symbioscience, the life-science division of Mars Inc., the company most famous for its chocolate products.
The researchers found that the flavanols improved vasodilation, the ability of the arteries to widen to allow more blood to flow, with no adverse effects. Rassaf said it's possible that the flavanols may stimulate the production of nitric oxide (NO), the chemical the body uses to increase blood flow during exercise or a "fight or flight" situation.
Chocolate lovers shouldn't get their hopes up, though. Rassaf told Live Science that the research doesn't imply that chocolate, which is also derived from cocoa, is good for the heart.
"The fresh cacao bean, from the cocoa pod or 'fruit,' is naturally rich in flavanols," Rassaf said. "However, cocoa flavanols are easily destroyed during the processing that occurs to make chocolate and other cocoa products. Therefore, chocolate actually does not typically contain consistent or significant levels of these compounds and should not be viewed as a reliable source of cocoa flavanols."
And, in fact, too much sugar-laden chocolate could lead to Type 2 diabetes, which may then lead to the kidney and heart problems for which cocoa, ironically enough, can help. Maybe that's a bitter bean to swallow.
Follow Christopher Wanjek @wanjek for daily tweets on health and science with a humorous edge. Wanjek is the author of "Food at Work" and "Bad Medicine." His column, Bad Medicine, appears regularly on Live Science.
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Christopher Wanjek is a Live Science contributor and a health and science writer. He is the author of three science books: Spacefarers (2020), Food at Work (2005) and Bad Medicine (2003). His "Food at Work" book and project, concerning workers' health, safety and productivity, was commissioned by the U.N.'s International Labor Organization. For Live Science, Christopher covers public health, nutrition and biology, and he has written extensively for The Washington Post and Sky & Telescope among others, as well as for the NASA Goddard Space Flight Center, where he was a senior writer. Christopher holds a Master of Health degree from Harvard School of Public Health and a degree in journalism from Temple University.