Vitamin D status is currently judged by serum 25(OH)D and the parathyroid hormone (PTH)-25(OH)D dynamic (1). The ultimate effect of vitamin D on human health is a healthy skeleton, which is characterized in infancy by normal linear growth and bone mineral accretion and absence of bone related disease, such as rickets (1). The importance of these indicators is illustrated in epidemiological research, where linear growth in infancy is positively related to peak bone mass as an adult (2). Moreover, both vitamin D status (3) and intake (4) in infancy are related to bone mass in children.