The National Institute of Health recommends adults not get more than 2000 IU of vitamin D a day. How vitamin D might slow agingVitamin D is known as the “sunshine vitamin” that may boost mental and bone health. “Vitamin D also supports the production of glutathione, your body’s master antioxidant. Your body gets vitamin D through sun exposure, which you naturally absorb safely in small increments, says Dr. Mercola. “Your body is built to regulate how much vitamin D it makes from sunlight,” he adds.