TFRC and vitamin A deficiency: In our lactating women, the retinol/RBP molar ratio was <0.8 in 44% of mothers indicating vitamin A deficiency, but the ratio exceeded 1 in 34% of women, indicating the likelihood of unbound, and potentially toxic, vitamin A. Moreover, we found that a higher retinol/RBP ratio increased the likelihood that sTfr would be >8.3 mg/L, indicating a need for iron supplementation when in fact the mothers may require more protein.