Nutritionally relevant supplementation of vitamin B6 in lactating women: effect on plasma prolactin.

Pharmacologic doses of vitamin B6 administered to lactating women have been reported to suppress plasma prolactin. As a result, some physicians have recommended restriction of vitamin B6 intake for lactating women. In the present investigation, 20 lactating women were given supplemental doses of vitamin B6, 0.5 to 4.0 mg/d, beginning 24 hours after delivery. Plasma prolactin, plasma pyridoxal phosphate, and breast milk total vitamin B6 concentrations were determined during the first 9 months postpartum. Women receiving the supplement of 4.0 mg compared with 0.5 mg of vitamin B6 per day had significantly higher plasma pyridoxal phosphate (P less than .01) and breast milk total vitamin B6 concentrations (P less than .05) beginning at 1 month postpartum and continuing through the duration of the study. Plasma prolactin concentrations were not significantly different between the two groups. The percentage of all women, regardless of treatment, in whom lactation persisted at 1 and 2 weeks and 1, 3, 6, and 9 months were 100%, 100%, 100%, 90%, 80%, and 65%, respectively. All women who ceased to lactate during the study reported doing so by choice. Nutritionally relevant doses of vitamin B6 elevated plasma pyridoxal phosphate and breast milk total vitamin B6 concentrations of lactating women without reducing plasma prolactin concentration or halting lactation.