Our bodies produce D in response to sunlight, so people far from the equator make less, especially during the long, dark winter months. (health.com)
This number rises to 74 % in the elderly and 82 % in people with dark skin, since their skin produces less vitamin D in response to sunlight (15, 16). (healthline.com)
The pigment melanin reduces the skin's ability to make vitamin D in response to sunlight exposure. (idmprogram.com)