Nutritional supplements and mother’s milk composition: a systematic review of interventional studies

Systematic review of interventional studies in lactating women (postpartum). Study designs included randomized controlled trials and quasi-experimental studies; quality assessed with Jadad scale and Cochrane risk-of-bias tools. Participants varied in age and health status; at least one trial described 24 healthy lactating women aged 20–36 years.

Overall, maternal vitamin/mineral supplementation can alter breast milk composition, with stronger and dose-dependent effects observed for vitamins than for minerals. Effects are more pronounced in colostrum than in mature milk. Vitamin A supplementation generally increases retinol and related carotenoids in milk; Vitamin D supplementation tends to raise 25(OH)D in milk. B vitamins (B1, B2, B6, B12) and vitamin C often increase their respective levels in milk, though some trials report no significant changes for certain B vitamins. Vitamin E supplementation raises alpha-tocopherol in colostrum and transitional milk but not consistently in mature milk. Vitamin K supplementation increases milk phylloquinone. Beta-carotene results are inconsistent across studies. Multivitamin results are variable. For minerals, zinc shows mixed results (some increases, some declines); iron generally shows no consistent change in milk iron (though lactoferrin/iron-binding capacity may rise); selenium often increases milk selenium. No difference between mega-dose and single-dose mineral regimens.

Large heterogeneity across studies with varied designs, dosing, supplement forms, measurement methods, and sample collection; many studies lacked randomization or blinding; small sample sizes; potential biases; no meta-analysis performed.