Vitamin D status does not influence the breast‐milk calcium concentration of lactating mothers accustomed to a low calcium intake

Abstract

Plasma 25-hydroxy-vitamin D and breast-milk calcium concentration were measured at 3 months of lactation in 60 Gambian mothers accustomed to a low calcium diet, of whom 30 were consuming a calcium supplement and 30 were receiving a placebo, and in 48 British mothers. The plasma 25-hydroxy-vitamin D concentration of the Gambian women was not affected by either calcium supplementation (supplemented, 64.4 +/- 2.5 nmol l(-1); placebo, 64.9 +/- 3.5 nmol l(-1); mean +/- SE) or season. The British average was lower (53.9 +/- 3.0 nmol l(-1), p = 0.004), owing to marked seasonal effects. The breast-milk calcium concentration was lower in The Gambia (supplemented, 5.38 +/- 0.13 mmol l(-1); placebo, 5.10 +/- 0.13 mmol l(-1); British, 6.93 +/- 0.15 mmol l(-1), p < 0.0001). There was no relationship between plasma 25-hydroxy-vitamin D and breast-milk calcium concentration in any group. There was no trend towards lower breast-milk calcium concentration in women with vitamin D status towards the bottom of the normal range or in British women during the winter. This study provides no support for the hypothesis that breast-milk calcium concentration is influenced by vitamin D status or that lactating women with a low calcium intake are at particular risk of vitamin D deficiency.