Hey, we're all about getting outdoors and enjoying mother nature! Going outside is associated with a wide variety of health benefits and something we definitely recommend and partake in, but relying on the sun for all your vitamin D needs may leave you lacking.
In many parts of the world, especially northern climates, you cannot make vitamin D outside year round due to the angle of the sun during different seasons. Because of this, UVB (responsible for vitamin D production) cannot penetrate the earth's atmosphere. This means you could stand outside all day long on the sunniest day and still not make the vitamin D you need.
In the regions closer to the equator, sunscreen and protective clothing (important to keep you safe from the potentially harmful rays of the sun) will block all UVB as well, making it impossible to synthesize vitamin D.