Consumption of dark roast coffee brew (500 ml/day) for 1 month caused a 23% reduction in DNA damage in white blood cells compared to baseline levels. DNA damage is known to accelerate the aging process and can lead to cancer (randomized controlled trial).
This data is consistent with epidemiological studies that have shown coffee consumption is associated with significantly longer telomeres, a biomarker for aging. DNA damage is known to accelerate telomere shortening. This randomized controlled trial showed that coffee lowers DNA damage and that would be expected to potentially slow telomere attrition.