Several recent European studies suggested that supplementing infants with vitamin D during their first year might prevent type 1 diabetes. A dose of 50 microg/day was associated with decreased diabetes risk in Finland, but the effectiveness of lower doses was not examined. The recommended dietary intake of vitamin D for U.S. infants is 5 microg/day and the tolerable upper level is 25 microg/day. There is no evidence that intakes between 5 and 25 microg/day would reduce diabetes incidence, but it would seem prudent to ensure that infants reach at least the lower end of this range.