Low Vitamin A Paves Road to Iron Deficiency

DAVIS, Calif.--According to a study published in the January issue of The Journal of Nutrition (135:27-32, 2005) (www.nutrition.org) low maternal levels of vitamin A may leave breastfed offspring at risk for iron deficiency. University of California researchers hypothesized low vitamin A intake during lactation elicits differential effects on mammary gland and liver iron transport and storage proteins, thus affecting the iron concentration in milk, but not maternal iron status.

A positive correlation between maternal iron status and iron levels in milk were observed in lactating women supplemented with both vitamin A and iron, but not with iron alone. The scientists fed rats either a control diet or a marginal vitamin A diet--containing one-tenth of the vitamin A given in the control diet--through mid-lactation. Effects on plasma, milk, liver and mammary gland iron and vitamin A concentrations, and divalent metal transporter-1 (DMT1), ferroportin (FPN), ferritin, and transferrin receptor (TfR) expression were determined. The rats fed the vitamin A diet were not vitamin A or iron deficient at the onset of the study.

Milk and liver vitamin A and iron levels, as well as mammary gland iron concentrations were lower, liver TfR expression was higher, and mammary gland TfR expression was lower in rats fed the vitamin A diet compared with rats fed the control diet. Liver Ft was unaffected, yet mammary gland ferritin was lower in the vitamin A fed rats compared with those on the control diet. Liver and mammary gland DMT1 and FPN protein levels were lower in the vitamin A rats compared with the control.

The researchers concluded the mammary gland and the liver respond differently to marginal vitamin A intake during lactation, causing iron levels in milk to become significantly decreased due to effects on mammary gland iron transporters, thereby putting the nursing offspring at risk for iron deficiency.