To reach optimal peak bone mass and continue building and maintaining bone tissue as you get older, there are several factors you should consider.
Calcium is an important component of bone. Therefore, it is important that we eat sufficient calcium to maintain our skeletons, but there is no evidence that taking more than this is helpful. There is controversy regarding what is an adequate intake, recent evidence suggesting that as little as 500 mg/day (2 servings of dairy products) is sufficient in adults, though some experts still recommend 1000 mg/day, or more. Many older people find it difficult to take 1000 mg/day in their diets, so use supplements. However, there are now several safety concerns related to calcium supplements, and the consensus is that calcium from the diet is to be preferred. People ingesting at least 2 servings of dairy products daily are likely to be receiving enough calcium.
Vitamin D is a substance made in the skin as a result of sunlight exposure. It facilitates absorption of calcium from the diet. When vitamin D levels are very low, mineralisation of bone is impaired. Individuals who never go outside (e.g. frail elderly), those who are veiled, and those who have dark skin are at risk of vitamin D deficiency, so might benefit from a vitamin D supplement. The use of supplements by those who are not deficient does not improve bone health. Most healthy European New Zealand adults living independently do not require vitamin D supplements.