Competing interests
J.I.O. and H.S. are employed by Mars, Incorporated, a company engaged in flavanol research and flavanol-related commercial activities. S.A.S. and A.M.B. received an unrestricted research grant from Mars, Incorporated. None of the other authors has a conflict of interest to declare. COSMOS is supported by an investigator-initiated grant from Mars Edge, a segment of Mars dedicated to nutrition research and products, which included infrastructure support and the donation of study pills and packaging.This article is a PNAS Direct Submission.