Vitamin D and the Breastfeeding Infant: Family Medicine Clinicians' Knowledge, Attitudes, and Practices

Nutritional Status of Breastfeeding Mothers and Impact of Diet and Dietary Supplementation: A Narrative Review

Adequate nutrition during breastfeeding is crucial for ensuring the good health of mothers and babies. Despite the high energy and nutrient demands of breastfeeding, lactating women are often vulnerable from a nutritional perspective. The nutritional focus during breastfeeding tends to be on the newborn, often neglecting the mother's diet. Therefore, in the present narrative review, nutrient intakes were compared with the dietary reference values (DRVs) proposed by the European Food Safety Authority (EFSA) as well as by the World Health Organization/Food and Agriculture Organization (WHO/FAO). In the diets of lactating mothers, dietary inadequacies were observed in the intake of some vitamins, such as folic acid, vitamin B12, vitamin A, and vitamin D, and in the intake of certain minerals like calcium, iron, and iodine; polyunsaturated omega-3 fatty acid deficiencies, primarily in eicosapentaenoic acid and docosahexaenoic acid, were also observed. On the other hand, the debate on the necessity of supplementation during lactation continues; the need for nutritional supplementation during lactation depends on many factors, such us mothers' eating habits. There seems to be a positive association between nutritional supplementation of the lactating mother and the concentration of certain nutrients in human milk. The present narrative review provides an update on the nutritional status (fatty acids and micronutrients) of breastfeeding mothers and the impact of diet and dietary supplementation on human milk composition.

Early-Life Effects of Vitamin D: A Focus on Pregnancy and Lactation

Vitamin D is an endocrine regulator of calcium and bone metabolism. Yet, its effects include other systems, such as innate and adaptive immunity. Unique to pregnancy, circulating 1,25-dihydroxyvitamin D (1,25[OH]2D) increases early on to concentrations that are 2-3 times prepregnant values. At no other time during the lifecycle is the conversion of 25-hydroxyvitamin D (25[OH]D) to 1,25(OH)2D directly related and optimized at ≥100 nmol/L. Vitamin D deficiency appears to affect pregnancy outcomes, yet randomized controlled trials of vitamin D supplementation achieve mixed results depending on when supplementation is initiated during pregnancy, the dose and dosing interval, and the degree of deficiency at the onset of pregnancy. Analysis of trials on an intention-to-treat basis as opposed to the use of 25(OH)D as the intermediary biomarker of vitamin D metabolism yields differing results, with treatment effects often noted only in the most deficient women. Immediately after delivery, maternal circulating 1,25(OH)2D concentrations return to prepregnancy baseline, at a time when a breastfeeding woman has increased demands of calcium, beyond what was needed during the last trimester of pregnancy, making one question why 1,25(OH)2D increases so significantly during pregnancy. Is it to serve as an immune modulator? The vitamin D content of mother's milk is directly related to maternal vitamin D status, and if a woman was deficient during pregnancy, her milk will be deficient unless she is taking higher doses of vitamin D. Because of this relative "deficiency," there is a recommendation that all breastfed infants receive 400 IU vitamin D3/day starting a few days after birth. The alternative - maternal supplementation with 6,400 IU vitamin D3/day, effective in safely raising maternal circulating vitamin D, that of her breast milk, and effective in achieving sufficiency in her recipient breastfeeding infant - remains a viable option. Additional research is needed to understand vitamin D's influence on pregnancy health and the effect of maternal supplementation on breast milk's immune signaling.

Vitamin D in Breastfed Infants: Systematic Review of Alternatives to Daily Supplementation

Daily oral vitamin D supplementation (400 IU) is recommended for breastfeeding infants (≤1 y). Recent studies have examined alternative approaches to preventing vitamin D deficiency in this population. This systematic review and meta-analysis aimed to estimate the effects of maternal postpartum (M-PP) or infant intermittent (I-INT) vitamin D supplementation on infant 25-hydroxyvitamin D [25(OH)D] concentrations in comparison to routine direct infant daily (I-D) oral supplementation (400 IU). MEDLINE, MEDLINE In-Process, Embase, the Cochrane Database of Systematic Reviews, and the Cochrane Central Register of Controlled Trials were searched up to December 2018. Inclusion criteria consisted of published, peer-reviewed, vitamin D intervention trials involving lactating women and/or exclusively or partially breastfed term infants. Two reviewers independently extracted study characteristics (e.g., sample size, intervention dose, and duration and mode of administration) and related biochemical and clinical outcomes. Of 28 included trials, 5 randomized controlled trials were incorporated in meta-analyses examining infant 25(OH)D. Overall, M-PP supplementation resulted in modestly lower infant 25(OH)D compared with I-D supplementation (weighted mean difference = -8.1 nmol/L; 95% CI: -15.4, -0.9; I2 = 45%; P = 0.14; 3 trials), but the 2 most recent trials found M-PP to achieve similar infant 25(OH)D as I-D. Comparison of I-INT with I-D was confined to 2 trials with contradictory findings, and it was considered inappropriate for pooled analysis. Meta-analysis was therefore limited by a small number of eligible trials with variable quality of analytically derived 25(OH)D data and inconsistent reporting of safety outcomes, including effects on calcium homeostasis. Considering all 28 included trials, this systematic review highlights M-PP and I-INT regimens as plausible substitutes for routine daily infant vitamin D supplementation, but evidence remains too weak to support a policy update. Dose-ranging, adequately powered trials are required to establish the efficacy, safety, and feasibility of alternative strategies to prevent vitamin D deficiency in breastfeeding infants. This review was registered with PROSPERO as CRD42017069905.