Low vitamin a intake affects milk iron level and iron transporters in rat mammary gland and liver.

Marginal vitamin A deficiency is common and can result in a secondary iron (Fe) deficiency. A positive correlation between maternal Fe status and milk Fe was observed in lactating women supplemented with both vitamin A and Fe but not with Fe alone, suggesting effects of vitamin A on mammary gland Fe transport. We hypothesized that low vitamin A intake during lactation elicits differential effects on mammary gland and liver Fe transport and storage proteins, thus affecting milk Fe concentration but not maternal Fe status. We fed rats a control (CON, 4 RE/g) or a marginal vitamin A diet (AD, 0.4 RE/g) through midlactation. Effects on plasma, milk, liver and mammary gland Fe and vitamin A concentrations, and divalent metal transporter-1 (DMT1), ferroportin (FPN), ferritin (Ft), and transferrin receptor (TfR) expression were determined. Dams fed AD were not vitamin A or Fe deficient. Milk and liver vitamin A and Fe and mammary gland Fe concentrations were lower in rats fed AD compared with rats fed CON. Liver TfR expression was higher, whereas mammary gland TfR expression was lower in rats fed AD compared with rats fed CON. Liver Ft was unaffected, whereas mammary gland Ft was lower in rats fed AD compared with rats fed CON. Liver and mammary gland DMT1 and FPN protein levels were lower in rats fed AD compared with rats fed CON. Our results indicate that the mammary gland and liver respond differently to marginal vitamin A intake during lactation and that milk Fe is significantly decreased due to effects on mammary gland Fe transporters, putting the nursing offspring at risk for Fe deficiency.