The prevalence of osteoporosis is increasing, and is a significant burden on society. Dietary composition is an important determinant of the bone mineral density in the growth period, and of the magnitude of the age related bone mineral loss, in particular among postmenopausal women. Therefore, an improvement of the diet has an important role in the prevention of osteoporosis. A sufficient intake of calcium and vitamin D can reduce the risk of fractures in postmenopausal women, and it is likely that a low calcium intake may affect peak bone mass negatively. Calcium in the Danish diet comes mainly from dairy products. Half a litre of milk and 25 g of cheese will cover most people's calcium requirement. Part of the calcium requirement may also be covered by consuming other foods such as cabbage, broccoli and beans. Children, adolescents and elderly individuals who avoid dairy products are recommended to take a calcium supplement. The status of vitamin D among the elderly can be improved by a daily outdoor stay and by a frequent intake of fatty fish such as herrings. Elderly persons who stay indoors are recommended to take a vitamin D supplement.