Vitamin D is important for good health, growth and strong bones. A lack of vitamin D is very common. Vitamin D is mostly made in the skin by exposure to sunlight. Most foods contain very little vitamin D naturally, though some are fortified (enriched) with added vitamin D. A mild lack of vitamin D may not cause symptoms but can cause tiredness and general aches and pains. A more severe lack can cause serious problems such as rickets (in children) and osteomalacia (in adults), described below. Treatment is with vitamin D supplements. Some people are more at risk of vitamin D deficiency, and so are recommended to take vitamin D supplements routinely. These include all pregnant and breast-feeding women, all babies and young children aged 6 months to 5 years, people aged 65 and over, and people who are not exposed to much sun. A doctor may also recommend routine supplements for certain people with darker skin, and for people with certain gut, liver or kidney diseases.