Vitamin D (also called calciferol) is a fat-soluble vitamin, which acts as a hormone. This means that it’s made in one place in the body but used elsewhere.
Most of the vitamin D your body uses is made under your skin when you’re exposed to the sun, but you also get it from food. Good dietary sources of vitamin D include fish oils, butter, egg yolks and liver.
Vitamin D helps to ensure strong bones by increasing the rate that minerals like calcium and magnesium are deposited into bones. It’s also crucial for the absorption of calcium from food.
Low vitamin D levels have been linked to an increased risk of osteoporosis, high blood pressure, diabetes and cancer. Recently, researchers have found an association between vitamin D levels and how well the lungs work.