In order to reach serum Vitamin D concentrations equivalent to ingesting approximately 20,000 IU of vitamin D2, one needs exposure to 1 minimal erythemal dose of simulated sunlight (the amount required to cause a slight pinkness of the skin, Holick MF. Vitamin D: the underappreciated D-lightful hormone that is important for skeletal and cellular health. Curr Opin Endocrinol Diabetes. 2002;9:87–98).
However, the majority of the adult living and working in the Northwest, the rain and clouds had severely limited us from reaching the recommended serum Vitamin D level. And with Vitamin D also closely related to other disease preventions, such as Osteoporosis, Colorectal Cancer, Breast Cancer, Prostate Cancer, Autoimmune Diseases, and Hypertension, isn't it time for you to look into Vitamin D supplements if you haven't already?