How to get vitamin d
Vitamin d is a hormone produced by the kidneys that helps to control the concentration of calcium in the blood and is vital for the development of strong bones. Complete cloud cover reduces uv energy by 50%; shade (including that produced by severe pollution) reduces it by 60% 20 uvb radiation does not penetrate glass, so exposure to sunshine indoors through a window does not produce vitamin d 21 sunscreens with a sun protection factor (spf) of 8 or more appear to block vitamin d-producing uv rays, although in practice people generally do not apply sufficient amounts, cover all sun-exposed skin, or reapply sunscreen regularly 1 , 22 therefore, skin likely synthesizes some vitamin d even when it is protected by sunscreen as typically applied. However, vegan or vegetarian children and adults who do not get enough vitamin d from foods or have low blood levels of vitamin d may need a vitamin d supplement. When the uv index is 3 or above (such as during summer), most people maintain a...