Cocoa Supplement and Multivitamin Outcomes Study (COSMOS)

Cocoa Supplement and Multivitamin Outcomes Study (COSMOS)

Cocoa beans

Cocoa flavanols, natural bioactive compounds in the cocoa bean, have been shown to have beneficial effects on cardiovascular disease (CVD) risk factors such as blood pressure, HDL and LDL cholesterol, insulin and inflammation, but we don’t know whether these effects will translate into real reductions in CVD rates.

Despite the prevalence of multivitamin use in the U.S. (over one-third of U.S. adults take multivitamins) they have not been shown to be effective at improving health. A recent large scale trial in male physicians found no effect on CVD but suggested that multivitamins reduced the risk of cancer by 8 percent. In older men (ages ≥ 70), the risk reduction was 18%.  We are interested in determining whether these commonly used supplements can help reduce the risk of cancer, particularly in older women.

Starting in 2015, the Women’s Health Initiative (WHI) is conducting a five-year, large-scale randomized controlled trial to test the effect of a concentrated cocoa extract and multivitamin supplements in reducing risks of CVD and cancer. This trial is the first study large enough to assess the effects of cocoa extracts and multivitamins on these health conditions that are so important in later ages. Researchers are interested in determining whether concentrated cocoa extract can help reduce heart disease and stroke and whether commonly used multivitamin supplements can help reduce the risk of cancer, particularly in older women.

Participants to be recruited from WHI

Participants are recruited from the WHI. However, there is a small chance that women not involved in the WHI may be eligible to participate. As a randomized controlled trial, participants will not know if they are taking cocoa flavanol supplements, multivitamin supplements or placebo pills. Placebo pills have no active ingredients.

The trial is coordinated by the Brigham and Women’s Hospital and the Fred Hutch. Involvement by Fred Hutch is through WHI, an ongoing nationwide study of postmenopausal women. This trial will showcase the ability of the WHI to conduct low-cost trials of non-invasive risk-reduction strategies in older populations by using the WHI's existing resources as the foundational structure.

The study is sponsored by Mars Symbioscience and Pfizer, Inc.

Study at a Glance

  • Cocoa supplement is a highly concentrated extract of cocoa flavanols. This is not a study about eating chocolate.
  • Multivitamin is a commonly used preparation
  • Participants will be randomized to the cocoa extract or placebo and at the same time to a multivitamin or placebo
  • Trial is randomized and controlled. Participants won't know if they are taking cocoa flavanol supplements, multivitamin supplements or placebo pills
  • Study is five years
  • The study is being sponsored by Mars Symbioscience and Pfizer Inc.

To ask questions, call 1-800-633-6913 or email to

Learn more about the Women's Health Initiative.

For adults who are interested in COSMOS and are not in the WHI, recruitment is primarily among persons who indicated interest in but did not enroll  in the VITamin D and OmegA-3 TriaL (VITAL) at Brigham and Women’s Hospital, an affiliate of Harvard Medical School, in Boston, Massachusetts. COSMOS is also open to men aged 60 and older and women aged 65 and older from the community. Detailed information about the study’s eligibility criteria, can be found at For more information, please send an email to