COcoa Supplement and

Multivitamin Outcomes Study

Welcome to the COSMOS Trial!


The COcoa Supplement and Multivitamin Outcomes Study (COSMOS)  at Brigham and Women’s Hospital – an affiliate of Harvard Medical School (Boston, MA) and the Fred Hutchinson Cancer Research Center (Seattle, WA) is a clinical trial that will randomize 18,000 men and women across the U.S. The study will investigate whether taking daily supplements of cocoa flavanols (600 mg/day) or a common multivitamin reduces the risk for developing heart disease, stroke, and cancer.


Although results from previous studies have been promising, the health benefits of taking these supplements have not yet been proven. The only way to determine whether or not cocoa flavanol and multivitamin supplements help maintain health is by conducting a large-scale trial, such as COSMOS.


To learn more about this important research endeavor, please click on Media and Q&A.


If I join COSMOS, what will I be asked to do?

Take 3 study pills every day for the next four years

Complete questionnaires about medical history, risk factors for heart disease and cancer, and diet

Forego outside use of cocoa extract supplements and multivitamins (you can still eat chocolate!)

Give study investigators consent to review medical records related to new diagnoses of heart disease or cancer during the trial


Who is eligible to participate?

Men 60 and older and women 65 and older living in the United States (excluding Puerto Rico) are eligible to participate.


Who is not eligible to participate?

Anyone who has ever had a heart attack or stroke, a new diagnosis of cancer in the past two years, or a major illness that would prevent them from completing a four year study is not eligible to participate.


Interested in joining the study?

Click here for more information.



Brigham and Women’s Hospital  | Division of Preventive Medicine | 900 Commonwealth Avenue  |  Boston, MA  02215  |  800-633-6913