Study Findings

Click one of the following to jump to that section of the page: Cocoa ExtractMultivitaminCOSMOS MindCOSMOS Web

COSMOS includes 21,442 participants –12,666 women aged 65 or older and 8,776 men aged 60 or older – who were followed for an average of 3.6 years through the end of 2020. These are the results for the studied cocoa extract and multivitamin supplements.

We now have the results of the largest and longest randomized trial of daily cocoa extract supplementation, and the largest trial of multivitamin supplementation, for the prevention of cardiovascular disease and cancer! The results were published in The American Journal of Clinical Nutrition (AJCN).

Cocoa Extract Findings

Read the published paper here: Final cocoa extract findings

Cocoa extract: During the trial, 410 out of 10,719 participants taking cocoa extract and 456 out of 10,723 participants taking placebo had confirmed total cardiovascular events – including heart attack, stroke, coronary revascularization, death caused by cardiovascular disease, unstable angina requiring hospitalization, carotid artery surgery and peripheral artery surgery. This translates to a modest 10% reduction in cardiovascular events for those taking cocoa extract, but it was not statistically significant.

However, additional analyses provided broader potential support for a benefit on cardiovascular events that highlight the need for more research. When comparing participants who remained compliant with the active cocoa extract and placebo groups, cocoa extract supplementation significantly reduced total cardiovascular events by 15%. Cocoa extract supplementation also reduced deaths due to cardiovascular disease, a pre-specified secondary endpoint, by 27%. Cocoa extract did not significantly reduce other individual cardiovascular outcomes. Participants taking cocoa extract experienced no significant effects on total invasive cancer, individual cancers, or cancer death.

Summary of Cocoa Extract Findings:

  • COSMOS provides the first suggestive evidence that long-term cocoa extract supplementation may favorably impact clinical cardiovascular outcomes, including a significant 27% reduction in cardiovascular death and greater cardiovascular benefits among those taking the study pills regularly.

  • Additional research is needed to understand how cocoa extract supplementation may reduce cardiovascular events through continued follow-up of COSMOS participants and ongoing ancillary studies examining mechanisms of effect along with other aging-related outcomes.

Multivitamin Findings

Read the published paper here: Final multivitamin findings

Multivitamin: During the trial, 518 out of 10,720 participants taking a multivitamin and 535 out of 10,722 participants taking placebo had confirmed total invasive cancers. This small nonsignificant difference meant that multivitamin use was not associated with risk of total invasive cancer.

When looking at individual cancers, rather than total, there was no significant effect of daily multivitamin use on reducing the occurrence of breast cancer, colorectal cancer, prostate cancer, or melanoma. However, daily multivitamin use did potentially reduce lung cancer by 38%, compared with placebo. Daily multivitamin use had no effect on cancer among those with a baseline history of cancer and had no effect on total major cardiovascular events or individual cardiovascular events. A daily multivitamin did appear to improve levels of several nutritional biomarkers.

Summary of Multivitamin Findings:

  • COSMOS did not find that a daily multivitamin reduced the risk of total cancer or cardiovascular disease among generally healthy older men and women.

  • Multivitamins are safe and remain the most frequently used dietary supplement, and future studies are needed to clarify its role on nutritional status and other aging-related outcomes.

COSMOS-Mind Findings

Read the published paper here: Final COSMOS-Mind findings

Vitamins, minerals, and other bioactives in foods are important for normal brain function, and deficiencies in older adults may increase risk for cognitive decline. Dietary supplements are often recommended for cognitive protection, but supporting evidence is mixed. COSMOS investigators partnered with colleagues at Wake Forest University to test whether daily use of cocoa extract or a multivitamin for 3 years can reduce the risk of cognitive decline. The COSMOS-Mind sub-study enrolled 2,262 COSMOS participants aged 65 and older who completed annual telephone interviews to assess memory and thinking abilities. The investigators found that cocoa extract did not affect cognition. On the other hand, daily multivitamin use improved cognitive function. That is, participants assigned to the multivitamin group had higher cognitive test scores after 3 years than the participants assigned to the multivitamin-placebo group. The investigators estimated that taking the daily multivitamin slowed cognitive aging by approximately 60%, or the equivalent of 1.8 years over the 3 years of the study, but this finding requires confirmation in future research. “COSMOS-Mind provides the first evidence from a large randomized trial to show that regular use of a typical daily multivitamin may improve memory and thinking abilities in older adults,” noted COSMOS Co-Director Dr. Howard Sesso, who leads COSMOS with Dr. JoAnn Manson. However, the story continues to unfold as other investigators complete separate studies in COSMOS that dig more deeply into the effects of both cocoa extract and a multivitamin on different aspects of cognition and other aging-related outcomes. Stay tuned!

COSMOS-Web Findings

Read the published papers here: Final COSMOS-Web multivitamin findings Final COSMOS-Web cocoa extract findings

COSMOS investigators at Brigham and Women’s Hospital worked closely with colleagues at Columbia University to test whether a daily multivitamin or cocoa extract supplement can impact memory through a novel web-based assessment. The COSMOS-Web sub-study enrolled more than 3,500 COSMOS participants who completed web-based assessments (different from those assessed in COSMOS-Mind) to assess memory and thinking abilities annually over 3 years.

The investigators found that daily multivitamin use resulted in improvements in cognitive function. More specifically, participants assigned to the multivitamin group did significantly better on the COSMOS-Web memory tests at the prespecified primary time point of 1 year. These benefits were maintained across all 3 years of follow-up. The investigators estimated that the multivitamin intervention improved memory performance by the equivalent of 3.1 years compared to the placebo group. “The findings that a daily multivitamin improved memory and slowed cognitive decline in two separate studies in the COSMOS randomized trial is remarkable, suggesting that multivitamin supplementation holds promise as a safe, accessible and affordable approach to protecting cognitive health in midlife and older adults,” said COSMOS Co-Director Dr. JoAnn Manson. In addition, COSMOS Co-Director Dr. Howard Sesso notes, “It is important to understand the mechanisms that explain how a daily multivitamin tested in COSMOS may protect against memory loss and cognitive decline, and whether particular subgroups based on nutritional status or other factors may benefit more, or less.”

For the cocoa extract intervention, the investigators found that cocoa extract supplementation did not affect the prespecified primary timepoint of cognition at 1 year or across all 3 years of follow-up. However, baseline nutritional status may matter for understanding the cognitive effects of the cocoa extract intervention. The investigators determined that COSMOS participants with comparatively lower levels of dietary flavanol intake (obtained through consumption of cocoa, tea, berries, grapes, and other foods) may have greater cognitive benefits from a cocoa extract supplement that contained dietary flavanols compared with those taking placebo. “These are promising and novel findings on the effects of a cocoa extract supplement to slow memory loss among those with lower initial dietary flavanol intake”, said COSMOS Co-Director Dr. Howard Sesso. Further, COSMOS Co-Director Dr. JoAnn Manson highlights that “COSMOS-Web is a model for the synergy possible between observational research and gold-standard randomized trials.”

FAQs about the Study Findings

What is next for COSMOS participants?

Ancillary study findings will be available soon and will allow more insight into the role of cocoa extract and multivitamin supplementation on other important areas of interest, including cognition, falls and physical performance, eye disease, COVID-19, and healthy aging. We will keep you informed of these results as they become available.

COSMOS participants are still part of an incredibly unique large-scale scientific endeavor to understand not only the long-term health effects of the randomized cocoa extract and multivitamin interventions, but also to deepen our understanding of healthy aging. We will continue to send questionnaires to COSMOS participants, as well as provide opportunities for involvement in other important sub-studies and new research studies.

Should I start taking cocoa extract supplements and/or a multivitamin?

We recommend speaking with your healthcare provider if you have questions about whether or not to take a multivitamin and/or cocoa extract supplement taking into consideration your individual health history and diet. It remains very important to have a healthy, balanced diet rich in fruits, vegetables, and other foods. These final results, as well as the ongoing ancillary studies from COSMOS, will create a more complete picture and help you and your doctor make a final decision. Our general guidance at this time is not to change whatever you are currently doing. For those taking either supplement, there were no safety concerns noted during the COSMOS trial.

Are the results tied to specific products? Should I expect the same effects with other similar products?

The multivitamin tested in COSMOS, Centrum Silver®, is very similar to the current Centrum Silver® Adults 50+ multivitamin which contains a comprehensive array of essential vitamins and minerals to help meet recommended daily intakes. The cocoa extract supplement used in COSMOS is similar to CocoaViaTM Cardio Health as they both include 500 mg cocoa flavanols, including about 80 mg (-)-epicatechin. We do not know whether the COSMOS results would apply to other multivitamin and cocoa flavanol supplements with similar or different amounts of nutrients.

Can I consume cocoa flavanols from chocolate?

Though cocoa is a key ingredient in milk and dark, but not white, chocolate, chocolate, variation in processing of the cocoa bean and its negative impact on flavanol content makes chocolate an unreliable source of flavanols. Chocolate products do not typically indicate their flavanol content, and darker or higher % cacao chocolate does not necessarily mean greater flavanol content. Importantly, it would be very difficult to consume the amount of cocoa flavanols studied in COSMOS from chocolate products without adding a large amount of fat, sugar and calories to your diet.

Were any side effects found for either of the study pills?

We found that both the multivitamin and cocoa extract supplements had a favorable overall safety profile. Based on self-reports, participants taking the active cocoa extract supplement were 6% more likely to have nausea, yet also had significant 5% reductions in flu-like symptoms and other headaches, as well as a larger 15% reduction in migraines. Participants taking active multivitamin had lower rates of self-reported stomach upset or pain, diarrhea, skin rash, and easy bruising and a higher rate of gastrointestinal bleeding compared to the placebo group.

Can you remind me which study pills I was assigned to?

Of course! Please contact us at 1-800-633-6913 or at if you have any questions regarding your pill-assignment.

What other studies can I participate in?

Going forward, you may be invited to participate in additional ancillary studies that will help examine the longer-term effects of cocoa flavanol supplements and multivitamins, and to explore other health-related topics. If you are interested in participating in any future trials within Harvard Medical School/Brigham and Women’s Hospital, feel free to contact us. You may also visit to view other clinical trials that are currently being conducted throughout the country.