Cocoa extract fails to prevent age-related vision loss, clinical trial finds

Brigham and Women's Hospital-led research reports no significant long-term benefit of cocoa flavanol supplementation in preventing age-related macular degeneration (AMD). The paper is published in the journal JAMA Ophthalmology.

AMD is a progressive retinal disease and the most common cause of severe vision loss in adults over age 50. AMD damages the macula, the central part of the retina responsible for sharp, detailed vision. While peripheral sight is typically preserved, central vision loss can impair reading, driving, facial recognition, and other quality of life tasks. Abnormalities of blood flow in the eye are associated with the occurrence of AMD.

Cocoa flavanols are a group of naturally occurring plant compounds classified as flavonoids, found primarily in the cocoa bean. These bioactive compounds have been studied for their vascular effects, including improved endothelial function and enhanced nitric oxide production, which contribute to vasodilation and circulatory health. Previous trials have shown that moderate intake of cocoa flavanols may lower blood pressure, improve lipid profiles, and reduce markers of inflammation, suggesting a role in mitigating cardiovascular and related vascular conditions.

In the study titled "Cocoa Flavanol Supplementation and Risk of Age-Related Macular Degeneration: An Ancillary Study of the COSMOS Randomized Clinical Trial," researchers conducted a double-blind, placebo-controlled randomized clinical trial to examine whether daily supplementation with cocoa extract prevents the development or progression of AMD.

A cohort of 21,442 U.S. adults (12,666 women aged 65 and older, and 8,776 men aged 60 and older) were recruited, with eligibility criteria requiring discontinuation of non-trial cocoa supplements and multivitamins for the 3.6-year duration of the trial. COSMOS included its own multivitamin supplement as one arm of the trial.

Daily supplementation consisted of 500 mg cocoa flavanols containing 80 mg (−)-epicatechin. Randomization assigned participants to either the cocoa extract or a matching placebo group. AMD outcomes were identified through self-reported diagnoses, verified through medical record confirmation. Compliance biomarkers confirmed a threefold increase in flavanol metabolite levels in the cocoa group.

A total of 344 participants experienced a confirmed AMD event, including 316 incident cases and 28 cases of progression. Incidence was 1.5% in the cocoa extract group and 1.7% in the placebo group.

Statistical modeling found a non-significant reduced risk during the first two years of treatment (HR, 0.77; 95% CI, 0.59–1.01), and a non-significant effect beyond two years (HR, 1.06; 95% CI, 0.76–1.50). Similar trends were observed in secondary outcomes.

In subgroup analyses, treatment effect varied by hypertension status, with a significant reduced risk in participants without hypertension (HR, 0.63; 95% CI, 0.44–0.92) and no significant findings among those with hypertension (HR, 1.04; 95% CI, 0.80–1.36).

Researchers concluded that cocoa extract supplementation had no significant overall effect on AMD risk over a median 3.6-year period. Although researchers did not rule out a possible early benefit trend, the findings do not support cocoa flavanol supplementation as a preventive strategy for AMD.

Study authors note that limited trial duration, modest dosage, and reliance on self-reported AMD diagnoses may have affected outcome sensitivity. Reduced clinical eye care during the pandemic may have led to underreporting of AMD diagnoses.

© 2025 Science X Network