This cross-sectional, quasi-interventional study (i.e., an interventional study without random treatment assignment) examined the relationship between vitamin D supplementation and DNA methylation age in 128 healthy German adults (ages 65–94).

To conduct this quasi-interventional study, the researchers used the longitudinal data (i.e., observational data that is collected sequentially over time from the same population) of 1,036 German adults from a previous cohort study.^[13] The treatment and control groups were selected so that both groups were vitamin D deficient at baseline but only the treatment group started vitamin D supplementation during the follow-up period. In other words, the researchers created the groups in such a way that vitamin D supplementation became the treatment. To allow for a valid comparison, the researchers matched the treatment and control groups based on age, sex, and morbidity. As a healthy control group, the researchers selected participants with sufficient vitamin D levels at baseline and throughout the entire follow-up period.

To determine the epigenetic age, the researchers measured five epigenetic clocks: the 7-CpG clock, Horvath’s clock, Hannum’s clock, PheoAge, and GrimAge. The researchers also calculated the difference between chronological age and epigenetic age.

Supplementation with vitamin D may be associated with slower epigenetic aging Original paper