In mammals the composition of milk changes during early lactation, with a rapid decline of fat-soluble vitamins and a continuous increase in total lipids. The mechanisms underlying this phenomenon are not well understood, but might involve selective mechanisms related to mammary uptake or secretion into the milk. Since carotenoids are specifically distributed among the lipoprotein fractions in plasma, the simultaneous determination of carotenoids in plasma, lipoprotein fractions and milk might offer an opportunity to gain insight into this phenomenon. In 21 healthy mothers carotenoids in plasma and lipoprotein fractions were investigated at day 2 and 19 and milk on day 4 and 19 after delivery. Plasma levels of alpha-tocopherol and cholesterol as well as lutein, zeaxanthin and cryptoxanthin were significantly lower later in lactation (day 19) than shortly after birth (P < 0.01). The stage of lactation had no effect on the distribution of carotenoids and alpha-tocopherol among the plasma lipoprotein fractions. In milk, triacylglycerol increased (P < 0.01). In contrast, levels of carotenoids, alpha-tocopherol and vitamin A were highest in colostrum and declined (P < 0.01). Because the magnitude of decrease was not the same in all carotenoids, the carotenoid pattern changed substantially. In colostrum the carotenoid pattern resembled those of plasma and the low-density lipoprotein fraction. In mature milk it was similar to the pattern found in the high density lipoprotein fraction. Based on these observations a selective mechanism might be responsible for the transfer of these components in milk involving different lipoprotein fractions at specific times of lactation.

An improved method for the extraction of the major carotenoids from human milk is described. Carotenoids were extracted from milk first with ethanol and n-hexane. Then, polar xanthophylls were extracted from n-hexane into ethanol/water. The remaining n-hexane was evaporated, the residue combined with the ethanolic milk fraction and the mixture briefly saponified. Carotenoids were extracted from the hydrolysate with n-hexane, combined with the polar xanthophylls from the non-saponified ethanol/water-extract and separated by HPLC. Using this method we were able to significantly improve the recovery of xanthophylls such as lutein and zeaxanthin from human milk. The recovery rate of all carotenoids was > 90%. This method might not only be of value for milk but should be especially useful in the extraction of carotenoids from human tissues such as the adipose tissue.