March 9 (UPI) -- A daily multivitamin may slow biological aging -- the rate at which our bodies age on a cellular level -- significantly, especially for people biologically older than their actual age. Researchers at Harvard Medical School and Mass General Brigham found that daily cocoa extract and multivitamin slowed biological signals that are predictive of mortality, they write in a study published in the journal Nature Medicine . Epigenetic clocks can estimate biological aging based on