To evaluate the molybdenum (Mo) status of infants in Japan, the Mo contents in human milk and formula milk were determined using inductively coupled plasma mass spectrometry (ICP-MS) and the average Mo intake of infants in Japan was estimated. Seventy-eight human milk samples were randomly collected from all over the country. The median, arithmetical mean, geometrical mean and range of Mo in these human milk samples were 2.9 ng/ml, 4.5 ng/ml, 3.4 ng/ml and 0.8 to 34.7 ng/ml, respectively. Based on these results, a reference range of Mo concentration of human milk in Japan was estimated to be 0.8 to 14.0 ng/ml. Analysis of Mo in seventeen human milk samples collected from 3 healthy volunteer showed that intra-individual variation was comparable to inter-individual variation in the Mo concentration. Mo concentration in Japanese formula milk was ranged to 1.1 to 2.4 ng/ml. Based on the Mo levels in human milk and formula milk, the Mo intake of Japanese infants was estimated to be 1 to 4 μg/day/capita.
