Vitamin D, DHA, Lactating Women and their Babies
Colostrum, the milk produced during the first few days of lactation, is particularly rich in nutrients needed by infants. The nutritional content of human milk continues to change during the course of the lactation and differs among women.
Human breast milk does not contain enough vitamin D (or vitamin K) to meet infant requirements. Two options exist. Both involve increasing vitamin D intake by 1) infants directly or 2) the mother to increase the vitamin D content of her breast milk. Hollis and colleagues report on vitamin D supplementation (400, 2400, or 6400 IU/d) and vitamin D status in nursing women and their breastfed babies. Results are also presented on breastfed infants who were orally supplemented with 400 IU/d as a liquid suspension.
Severe vitamin D deficiency was more prevalent in African American infants. Although not statistically significant, women receiving 400 IU daily were more likely to have insufficient vitamin D status (< 50 nmol/L) than their peers who were receiving 6,400 IU/d. During lactation, serum 25(OH)D concentrations decreased (-6.5 nmol/L) in women receiving 400 IU daily and increased (+51.3 nmol/L) in the 6400 IU group. At 1 month of age, >70% of infants had vitamin D concentrations below IOM recommendations (50 nmol/L). Blood vitamin D concentrations were similar among breastfed infants whose mother was consuming 6400 IU daily and infants being supplemented with 400 IU/d orally.
Hollis and colleagues write that current vitamin D dietary recommendations fail to “sustain blood concentrations of the parent vitamin D compound, the form that crosses from the maternal circulation into human milk; thus minimal vitamin D is transferred into human milk. The result: dire vitamin D deficiency in the breastfeeding infant, especially darker-pigmented infants. Our study clearly demonstrates that with appropriate vitamin D intake, the lactating mother can fully transfer from her blood to her milk the vitamin D required to sustain optimal vitamin D nutrition in the nursing infant.”
Since this study was initiated, the IOM increased the limit to 4000 IU per day and the Endocrine Society set an upper limit at 10,000 IU/d. The authors write, “To our knowledge, not a single adverse event has been attributed to vitamin D supplementation at the doses ranging from 2000 to 6400 IU/d.
A similar situation may prevail with respect to the long-chain polyunsaturated omega-3 fatty acid, docosahexaenoic acid (DHA). Unless nursing mothers consume more than typical amounts of fatty fish, their red blood cell omega-3 content (omega-3 index) will be low which can affect the DHA content of human milk.
Pregnant and lactating women need to sustain adequate circulating vitamin D and omega-3 concentrations in human milk to ensure nutrient requirements of breastfed infants are met.
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