The “sunshine vitamin” is important for more than just healthy bones. Vitamin D is essential for too many functions in the body to mention, and it is essential for normal immune function. Vitamin D is created in the skin with exposure to UV rays of sunlight. Because most people have low sun exposure (or use sunscreen, which blocks vitamin D production), low vitamin D levels are common.
Full sun exposure, best between 10 a.m. and 2 p.m., 30 minutes to an hour every day to the arms, chest, and face without sunscreen is generally adequate to maintain vitamin D levels. Aging and chronic disease also seem to adversely affect the ability of the body to generate vitamin D from sunlight. Though the best source of vitamin D is sunlight, supplementation is often necessary.
Suggested Dosage: During the winter months especially, supplements are the only way to maintain adequate levels. People living in southern locations generally need 1000-2000 IU daily, whereas northern locations often require 4000 IU or greater. Dark-skinned people also often require larger amounts of vitamin D. Vitamin D3 is the preferred form of supplementation. The best way to know if vitamin D levels are adequate is by having blood levels checked regularly—about every 6 months is ideal. Target a level of > 40 ng/ml.