Submitted to: The American Journal of Clinical Nutrition
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/16/1998
Publication Date: N/A
Interpretive Summary: Little is known about the metabolism of dietary chromium in breast-feeding mothers. We gave lactating mothers oral doses of an enriched stable (non-radioactive) isotope of chromium for three consecutive days. This served as a "tracer" for chromium, allowing us to follow the doses in the body by measuring the tracer in blood, blood serum, urine, and breast milk. .The tracer showed up in the serum within two hours, and was detectable for at least another month. None of the tracer doses were detectable in breast milk, and the amount of total chromium in breast milk did not respond to the doses, suggesting that the chromium content of breast milk is tightly controlled. The chromium tracer appearing in the urine was the same as for women who were not lactating. These results suggest that the chromium losses by the mother during breast feeding are not compensated for by increased absorption nor decreased excretion of the element. This information will be important to nutritionists, dietitians, and pediatricians.
Technical Abstract: To determine the fate and distribution of chromium during lactation, 6 post partum lactating women (25-38 years) were given 3 doses of tracer 53-Cr (7.55 umol/d) (400 ug/d)) on days 1, 2 and 3. Diet records, fasting blood, 24 hour composite milk and urine samples were collected from day 0 to day 6. On days 8, 10, 15, 30, 60, and 90 fasting blood, morning milk and 24 hour urine samples were collected. 53-Chromium, natural and total Cr concentrations in the biological fluids were determined using gas chromatography mass spectrometry and total urinary Cr using atomic absorption spectrometry. Tracer 53-Cr was detectable in serum 2 hours after the dosing and continued to be detected between days 30 to 60 days. Changes in the total serum Cr concentration in response to the oral dose suggest that Cr concentration in blood was not tightly regulated. Tracer Cr concentrations in milk were observed in response to the oral dose. This ssuggests that Cr concentration in breast milk is independent of the dose and is tightly regulated. The Cr intake of exclusively breast fed infants was 2.5 nmol/d (0.13 ug/d) which was below the minimum ESADDI (10-40 ug/d) for infants for 0.6 months of age. The baseline Cr concentration in urine and the minimum tracer 53-Cr absorption in lactating women were comparable to non-pregnant non-lactating subjects. Hence, increased absorption and decreased excretion are not ways by which Cr losses in breast milk are compensated.