Dr. Holick explains how a woman's vitamin D intake is reduced by using SPF 15.
So it turns out that SPFs will absorb ultraviolet radiation and prevents you from making vitamin D. It doesn’t prevent you from absorbing vitamin D, and so SPF of 15 reduces your ability to make vitamin D in your skin by 95 to 99%, if you use it properly.
About Dr. Holick, Ph.D., M.D.:
Michael Holick, Ph.D., M.D., is the Professor of Medicine of Physiology and Biophysics at Boston University School of Medicine. He received his medical degree from the University of Wisconsin, Madison and performed his residency and fellowship at Massachusetts General Hospital. Dr. Holick specializes in vitamin D, calcium, bone metabolism, photobiology of vitamin, and osteoporosis. Dr. Holick is also the recipient of the American Skin Associations Psoriasis Research Achievement Award, the American College of Nutrition Award, the Robert H. Herman Memorial Award in Clinical Nutrition from the American Society for Clinical Nutrition, and more.