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Major Carotenoids in Mature human Milk: Longitudinal and Diurnal Patterns

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Abstract

The present study was undertaken to quantitate the major carotenoids in human milk, monitoring their variance among fore, mid, and hind mature milk samples; during morning, midday, and evening, and among different weeks of lactation. Twenty-three mothers, 6 weeks to 16 weeks postpartum, participated in the study.

Reversed-phase high performance liquid chromatography (RP-HPLC) was used to identify and quantitate the major carotenoids found in human milk, including lutein/zeaxanthin, beta cryptoxanthin, lycopene, alpha carotene, and beta carotene. To determine the validity of analyzing carotenoids in frozen milk, freshly expressed and subsequently frozen milk samples were analyzed for four mothers. Freezing did not alter carotenoid concentrations.

Wide variations in carotenoid concentrations existed within and between the mothers. Major carotenoid totals ranged from 29 nM to 493 nM. Complete breast expressions at three periods within a day and at specified weekly intervals allowed the accurate determination of diurnal as well as longitudinal carotenoid concentrations. Diurnal evaluation of carotenoid concentrations suggested a peak at midday and highest longitudinal concentrations were at 10 to 12 weeks. Neither of these trends was statistically significant. The analysis of fore, mid, and hind milk carotenoid concentrations demonstrated that hind milk was significantly higher than fore or mid milk (P < 0.05).

Introduction

Human milk is the preferred source of nourishment for infants because it contains a variety of nutrients not universally found in infant formula or bovine milk. Among the nutrients contained in human milk are carotenoids, which may offer enhanced protection to the infant against infection.1, 2 Beta carotene and some of the other carotenoids are important because they are precursors of vitamin A, (required for normal growth and eyesight as well as resistance to infection) may enhance immune functions, impart antioxidant action, and demonstrate anticancer properties.3, 4, 5 The major carotenoids include beta carotene, alpha carotene, lycopene, beta cryptoxanthin, and lutein/zeaxanthin, all of which are supplied to the infant during breast feeding.6, 7 Beta carotene, comprising approximately 25% of the total carotenoid content in human milk, has the highest vitamin A activity of all known carotenoids and is a potent antioxidant.4, 8, 9

Serum concentrations of carotenoids in breast fed infants increase significantly starting 2 days after birth, whereas carotenoid concentrations in many formula fed infants decrease because of a lack of carotenoid fortification in most infant formulas.[1] A few infant formulas are fortified with beta carotene, thereby increasing the serum beta carotene concentrations in formula-fed infants, although total carotenoid concentrations are higher in breast fed infants.[10] Undernourished children often have serum concentrations of vitamin A and carotenoids much lower than found in well nourished children and often have serious health problems.[11] One could speculate that these children would benefit from a consistent diet rich in carotenoids.

Many previous studies quantitating carotenoids in human milk have used pooled milk from several donors or partial emptying of the breasts.[12] Complete emptying of the breasts is the preferable method for obtaining representative samplings of human milk used for the analysis of lipid-soluble compounds such as carotenoids. The lipid content of human milk is known to vary within a feed and diurnally.13, 14, 15, 16 Neville et al reported that lipid concentrations increased two- to three-fold between fore and hind milk.[14] This within feed variation of lipids was also observed by Hall, who cited that concentrations increased three fold.[13] Hall also reported diurnal variations in lipid concentrations, being lowest at 6 AM and highest at 2 PM with a 2.5-fold increase. It is conceivable that variations in carotenoid levels within a feed and diurnally could be related to the variations in lipid concentrations.

The present study analyzed full breast expressions of mature milk both diurnally and longitudinally. Expressions were collected in 30 mL fractions, which allowed the examination of fore, mid, and hind milk. We examined the validity of analyzing frozen milk samples by comparing carotenoid concentrations in freshly expressed milk and subsequently frozen samples.

Section snippets

Subjects

Subjects were recruited through a local breast-feeding support group. All participants were healthy adults, either primipara or multipara women. All delivered full-term infants and were lactating for at least 6 weeks. Informed consent was obtained from all participants and procedures followed were in accord with standard collection techniques recommended by breast pump manufacturers and used by many hospitals. Subjects were provided with individualized instructions regarding the study and use

Results and Discussion

This is the only published report examining total major carotenoid concentrations in human milk diurnally and longitudinally, the effects of freezing on carotenoids in fresh milk and concentrations of fore, mid, and hind human milk using modern technology. Reversed-phase HPLC was used to analyze the carotenoids. It allowed the simultaneous quantitation of lutein/zeaxanthin, beta cryptoxanthin, lycopene, alpha carotene, and beta carotene. Because of the short retention time and structural

Conclusion

Our findings demonstrate that total carotenoid concentrations in mature human milk seem to remain fairly constant diurnally and longitudinally. Longitudinal carotenoid concentrations in human milk have not been reported previously. Consequently, this study is significant in that it gives a more complete carotenoid profile of human milk than has been reported previously. Variations in carotenoid concentrations existed within and between the mothers; however, variations between mothers were much

Acknowledgements

The authors thank Dr. Ken Goldberg for statistical analysis of all the data and Judy Seibert for her expert secretarial assistance.

References (17)

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