Supplementing with 4,000 IU of vitamin D per day for 16 weeks reversed epigenetic aging by 1.85 years in overweight and obese African Americans that were low in vitamin D (randomized-placebo controlled trial).

Epigenetic marks follow a certain pattern with age. Blood samples were taken from individuals ranging from 19 years old to 101 years old and the methylation patterns analyzed. Based on the methylation patterns of the blood cells researchers were able to identify the age of the individual with 96% accuracy within about 4 years. This is known as the “Horvath epigenetic clock.”