Evidence for an interaction between exercise and nutrition for improved bone health during growth.

Exercise and nutrition are independently recognized as important modifiable lifestyle factors essential for optimal bone health during growth. In this review, we discuss the effect of dietary calcium, vitamin D and protein alone and in combination with exercise on bone mass and strength in children and adolescents. Recent intervention studies in children now provide evidence that exercise and calcium may interact with each other to enhance bone health, but the mechanism underlying this effect is not well understood. Vitamin D is also important for bone health through its action on calcium absorption, and both dietary protein and total energy intake can also alter bone metabolism through their influence on growth factors such as insulin-like growth factor I. However, whether these factors act synergistically with exercise to enhance bone accrual has not been examined. Therefore, while exercise and nutrition are both independently important for skeletal development, there remain many unanswered questions as to whether combinations of these factors interact to enhance skeletal health during growth. Current evidence suggests that regular weight-bearing exercise and adequate dietary calcium intakes (around 1,000 mg per day) may be required to optimize bone health; however, exercise would appear to be more important for optimizing bone strength because it has a direct effect (e.g. via loading) on bone mass and structural properties, whereas nutritional factors appear to have an indirect effect (e.g. via hormonal factors) on bone mass.