Human-milk vitamin B-3 (niacin and vitamer) concentrations: secondary analysis of a randomized, placebo-controlled trial of maternal nicotinamide supplementation in rural Tanzania.

backgroundThe risk of vitamin B-3 (niacin) deficiency is increased if maize is consumed without improving bioavailability during food preparation and with limited consumption of niacin-rich foods.

objectivesWe assessed human-milk vitamin B-3 concentrations and their relationship to child outcomes as a secondary analysis of a randomized controlled trial of nicotinamide supplementation to lactating mothers in rural Tanzania.

methodsThe Early Life Interventions for Childhood Growth and Development in Tanzania study, conducted in Haydom, Tanzania, randomly assigned lactating females to supplemental nicotinamide (250 mg/d compared with placebo) from study entry (infant age <2 wk) until 6 mo. Among 1173 mother/child dyads, human-milk nicotinamide and B3 vitamer concentrations at lactation months 1 and 5 were compared with international reference limits (fifth and 95th percentile) from the recent Mothers, Infants and Lactation Quality study, and child anthropometry and cognitive development [Malawi Developmental Assessment Tool (MDAT)] relationships were assessed.

resultsThe proportion of human-milk total vitamin B-3 concentrations below the lower reference limit increased over time in both those without and with nicotinamide supplementation (2.9% compared with 0.5% ≤0.720 mg/L at 1 mo; 28.8% compared with 9.9% ≤0.549 mg/L at 5 mo). Maternal nicotinamide supplementation was associated with many participants having human-milk total vitamin B-3 concentrations exceeding the upper reference limit (72.9% ≥3.284 mg/L at 1 mo; 50.7% ≥2.760 mg/L at 5 mo), and a sustained higher median concentration with supplementation compared with placebo (by 291% at month 1 and 281% at month 5). No associations were observed between human-milk total vitamin B-3 or vitamer concentrations and child weight, height, or head circumference ≤18 mo or with MDAT scores at 18 mo.

conclusionsWithout maternal nicotinamide supplementation, lactating females had a greater prevalence of human-milk total vitamin B-3 concentrations below the fifth percentile reference limit. Although supplementation was associated with greater total vitamin B-3 and vitamer concentrations, there was no association between human-milk vitamin B-3 and child growth or development outcomes ≤18 mo. This study was registered at clinicaltrials.gov as NCT03268902.