Depressed Folate Incorporation into Milk Secondary to Iron Deficiency in the Rat

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Abstract
The present study was designed to determine whether reduced folate incorporation into milk can account for folate depletion of iron-deficient suckling rats. Dams were fed diets containing 2 mg/kg folate and either 8, 12 or 250 mg/kg iron throughout gestation and lactation to produce severely iron-deficient, moderately iron-depleted and iron-sufficient states in 17-d-old pups (n = 15 litters/group). On d 17 of lactation, dams were separated from litters and given intraperitoneal injections of [3′,5′,7,9-3H]pteroylmonoglutamic acid ([3H]PteGlu) or physiological saline. Mean [3H]PteGlu incorporation into milk of severely iron-deficient dams was 67% of that in iron-sufficient controls, while “total” and “free” milk folate activities were 54 and 61%, respectively. Values for milk [3H]PteGlu incorporation and folate activities were intermediate in moderately iron-depleted dams. Pup red blood cell folate activity was positively correlated with both free (r = 0.43, P = 0.004) and total (r = 0.37, P = 0.015) milk folate activities. Mean plasma folate activities of severely and moderately iron-deficient pups were 68 and 86% of control values, respectively. Results show that in both mild and severe iron deficiency, reduced folate secretion into milk is at least partially responsible for impaired folate status of suckling pups.