Nowadays most infants on exclusively breast feeding have vitamin D deficiency due to the increase of breast feeding. However, domestic research lacks appropriate materials. Therefore, we researched practical clinical aspects of vitamin D deficiency related to breast milk feeding for infants who have a high amount of alkaline phosphatase (> 500 IU/L).

The subjects of the study were 31 infants with high alkaline phosphatase level. We tested with 25-hydroxycholecalciferol (25-OHD₃), parathyroid hormone, calcium, ionized calcium, phosphorus in their blood and with a wrist x-ray. Then, we divided them into two groups of breast feeding and formula feeding and compared the results.

Eighteen infants (58%) out of 31 infants that have high alkaline phosphatase were vitamin D insufficiency or deficiency, and 16 (100%) breast feeding infants of them showed vitamin D deficiency or insufficiency. However, only 2 (13%) of 15 formula feeding infants were at insufficiency. There was a correlation between alkaline phosphatase and 25-OHD₃ concentration in multiple regression analysis, but no correlation in other variables was found in group of breast milk feeding infants. There was neither correlation between vitamin D concentration and alkaline phosphatase nor other correlated variables in the group of formula milk feeding infants.

In this study, there was a high probability of vitamin D deficiency in the breast feeding infants with a high alkaline phosphatase level. Therefore, it is considered to be worth utilizing alkaline phosphatase as a screening test for vitamin D deficiency or rickets for breast feeding infants.