Predisposition to poor skeletal health resulting in osteoporotic fracture is a major public health problem, the future economical impact of which is likely to be phenomenal. Two mechanisms principally determine adult bone health: (1) maximum attainment of peak bone mass (PBM); (2) the rate of bone loss with advancing age. Both aspects are regulated by a combination of endogenous and exogenous factors, and although genetic influences are believed to account for up to 75% of the variation in bone mass, there is still room for modifiable factors to play a vital role. Weight-bearing physical activity is beneficial to the skeleton, but clarification of the exact type, intensity and duration required for optimum bone mass is needed. Excessive levels of exercise, which result in amenorrhoea, are detrimental to skeletal health. The importance of Ca to bone remains controversial. There is evidence that Ca is effective in reducing late post-menopausal bone loss, but more research is required on the long-term benefit of increased Ca intake on PBM attainment. Vitamin D 'insufficiency' appears to be widespread amongst population groups and is an area of considerable public health concern. The role of other micronutrients on bone metabolism remains to be fully quantified, but data from a combination of experimental, clinical and observational studies suggest a positive link between alkaline-forming foods and indices of bone health. The influence of nutrient-gene interactions on the skeleton requires further elucidation, but it may be useful in the future to target nutrition advice at those individuals who are genetically susceptible to osteoporosis.