Dr. Holick describes when the human body makes vitamin D.
You cannot make vitamin D in your skin in the early morning and late afternoon, and that’s why I typically recommend that if you want to take advantage of the beneficial effect of sunlight, it needs to be between the hours of 10:00 a.m. and 3:00 p.m.
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.