A new study led by Brigham and Women’s Hospital has found that taking cocoa flavanol supplements does not significantly reduce the risk of developing age-related macular degeneration (AMD), a leading cause of vision loss in people over 50.
The findings, published in JAMA Ophthalmology, suggest that cocoa flavanols are not an effective long-term preventive measure for this common eye condition.
AMD is a disease that slowly damages the macula—the central part of the retina responsible for sharp, detailed vision. While people with AMD usually keep their side (peripheral) vision, the loss of central vision can make it hard to read, recognize faces, drive, or perform everyday tasks. Changes in blood flow in the eye are linked to the development of AMD.
Cocoa flavanols are natural compounds found in cocoa beans. They are known for their effects on blood vessels, such as improving blood flow and lowering inflammation. Because of these properties, scientists have studied them as potential treatments for heart and blood vessel conditions.
Earlier research showed they might help with blood pressure and cholesterol, so researchers wondered if they could also help prevent AMD, a disease connected to blood vessel function in the eye.
In this study, researchers wanted to see if taking cocoa flavanols daily could help prevent AMD or slow its progression. The study was part of the larger COSMOS trial (Cocoa Supplement and Multivitamin Outcomes Study), which involved 21,442 older adults across the United States.
The participants included 12,666 women aged 65 and older and 8,776 men aged 60 and older. To take part, participants had to stop taking other cocoa supplements and multivitamins during the trial period.
The study was randomized and placebo-controlled—meaning that some participants were given real cocoa extract supplements, while others received look-alike placebo pills that contained no active ingredients.
The cocoa extract contained 500 mg of cocoa flavanols, including 80 mg of a key compound called (−)-epicatechin. Participants were followed for an average of 3.6 years. Researchers tracked the development of AMD based on self-reported diagnoses, which were later confirmed through medical records.
Over the course of the study, 344 participants developed AMD—316 of them were new cases, and 28 were people whose condition had worsened. In the group taking cocoa flavanols, 1.5% developed AMD, while 1.7% of those taking the placebo developed the disease. This small difference was not statistically significant.
During the first two years of the study, researchers saw a slight trend toward reduced risk in the cocoa group, but the result was not strong enough to confirm a real effect. After two years, there was no evidence of benefit at all.
Interestingly, in a subgroup of participants without high blood pressure (hypertension), the cocoa flavanols did appear to lower the risk of AMD (by 37%), but this effect was not seen in those with hypertension.
Researchers say there are several possible reasons why the trial didn’t show a stronger benefit. First, the trial period may not have been long enough to detect meaningful changes in AMD risk. Also, the dosage may have been too low to make a real difference.
In addition, the use of self-reported AMD diagnoses and the impact of the COVID-19 pandemic—which led to fewer eye doctor visits—may have led to underreporting or missed cases.
Review and Analysis
This study is one of the largest and most carefully designed trials to investigate the effects of cocoa flavanol supplements on eye health in older adults. While cocoa flavanols have shown promise in improving blood flow and reducing inflammation—factors involved in AMD—this trial did not find enough evidence to support their use for AMD prevention.
The early hint of benefit in people without high blood pressure is interesting, and it may point to a group that could benefit more from this kind of supplement. However, without stronger results, the overall conclusion is that cocoa flavanols should not be recommended as a preventive treatment for AMD at this time.
This study also highlights the importance of looking at the big picture in medical research. A natural compound may have some benefits in certain areas, but that doesn’t always mean it will help with all diseases linked to those areas.
As the authors note, longer trials, higher doses, and more accurate tracking of eye health may be needed to fully understand the role cocoa flavanols could play in vision care.
For now, people concerned about AMD should focus on proven strategies, such as not smoking, managing blood pressure, wearing UV-protective sunglasses, and eating a healthy diet rich in leafy greens and fish. Regular eye check-ups remain essential, especially for adults over 50.
If you care about eye health, please read studies about how vitamin B may help fight vision loss, and MIND diet may reduce risk of vision loss disease.
For more information about eye disease, please see recent studies about how to protect your eyes from glaucoma, and results showing this eye surgery may reduce dementia risk.
The research findings can be found in JAMA Ophthalmology.
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