RC Tsang

Bone mass peaks by age 17 years. Factors such as vitamin D status, mineral intake, exercise and genetics are important factors affecting bone mass. There are notable (two to threefold) seasonal variations in vitamin D status in infancy. Bone mass is markedly affected by season, even at birth. Breast milk vitamin D content is low and is affected by UV exposure and diet. Milk formula intake with varying calcium and phosphate concentrations has major effects on infant bone mass, the long-term consequences are unclear. Exercise and early motor development affect bone mass. Body weight is a significant variable for bone mass in infancy and childhood. Race differences in bone mass occur already at 1 year of age and there are associated marked differences in vitamin D metabolism and serum minerals between races. Pregnancy and lactation exert significant effects on bone-regulating hormones and bone mass. Lactational losses in bone mineral content are restored during the weaning process. Since peak bone mass is achieved prior to adulthood, it is important to understand the variables affecting bone mass and to consider strategies that might enhance bone mass in early life.