Transfer of selected elements from food into human milk

OBJECTIVES: We measured the transfer factors of antimony, cerium, chromium, cobalt, gallium, lanthanum, molybdenum, niobium, ruthenium, silver, thorium, titanium, and uranium from food to milk in nursing mothers. METHODS: Food and milk samples from 19 mothers were taken daily over 2 to 8 wk. The samples were analyzed for element content after microwave-assisted pressure digestion with a mass spectrometer and inductively coupled plasma. The transfer factor, or the portion of element intake passed on in the milk, was calculated as the element concentration in food (g/kg) divided by the element concentration in milk (g/L). RESULTS: The calculated transfer factors were 5.1 for silver, 16.1 for cerium, 6.9 for chromium, 8.4 for cobalt, 19.1 for gallium, 13.8 for lanthanum, 77.4 for molybdenum, 20.7 for niobium, 4.1 for ruthenium, 13.2 for antimony, 20.2 for thorium, 5.6 for titanium, and 21.3 for uranium. Factors differed significantly across individuals. CONCLUSION: These differences can be attributed to the fact that the different levels of elements in breast milk are the result of individual differences in milk production and factors other than the amount of any particular element absorbed by the body.