Maternal Factors Affecting the Vitamin D Content of Human Milk

Abstract

The antirachitic activity of human milk has been estimated using a variety of techniques during the past several years (1–9). The earlier studies were dependent upon the rat line biological assay to provide crude estimates of total antirachitic activity (1–3). Later studies utilized chemical methods that proved to be totally unreliable in estimating the vitamin D content of human milk (4–6). Only recently has the actual vitamin D content of human milk been determined using procedures based on high-performance liquid chromatography (HPLC) and/or competitive protein binding assay (CPBA) (7–13). These techniques have demonstrated: 1) that vitamin D sulfate does not contribute to the antirachitic activity of human milk; 2) that many vitamin D compounds exist in human milk; 3) of the vitamin D compounds in human milk 25-hydroxyvitamin D (25-OH-D) contributes the vast majority of antirachitic activity; 4) that maternal factors such as diet, ultraviolet light exposure and race greatly affect the vitamin D content of human milk. This last aspect, the effect of maternal vitamin D status on the vitamin D content of her milk, is relatively new and has not been reported in great detail. Thus, it is the purpose of this report to provide a detailed and comprehensive review of this area of nutritional investigation.