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Nutrient Physiology, Metabolism, and Nutrient-Nutrient Interactions

Xanthophyll and Hydrocarbon Carotenoid Patterns Differ in Plasma and Breast Milk of Women Supplemented with Red Palm Oil during Pregnancy and Lactation¹

Georg Lietz^*,2, Generose Mulokozi, Jeya C. K. Henry^** and Andrew M. Tomkins

^* Newcastle University, School of Clinical Medical Sciences, Newcastle upon Tyne, NE1 7RU, UK; Tanzania Food and Nutrition Centre, Dar es Salaam, Tanzania; ^** School of Biological and Molecular Sciences, Oxford Brookes University, Oxford OX3 0BP, UK; and Centre for International Child Health (CICH), Institute of Child Health, London WC1N 1EH, UK

² To whom correspondence should be addressed. Email: georg.lietz{at}ncl.ac.uk.

	ABSTRACT

TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Currently limited information exists on how maternal supplementation with provitamin A carotenoids might influence the carotenoid pattern in breast milk during lactation. This study was designed to investigate the effect of maternal red palm oil supplementation (12 g/d) throughout the 3rd trimester of pregnancy and the first 3 mo postpartum on carotenoid pattern in both plasma and breast milk. Plasma and breast milk - and ß-carotene concentrations increased in response to red palm oil supplementation and were different (P < 0.001) from the control group at both 1 and 3 mo postpartum. Plasma lutein and zeaxanthin concentrations were reduced (P < 0.001) from pregnancy to 1 mo postpartum and remained stable until 3 mo postpartum. However, breast milk lutein concentrations, expressed per gram of milk fat, increased (P < 0.05) in both groups from 1 to 3 mo postpartum. The results of this study show that there are proportionally more hydrocarbon carotenoids such as - and ß-carotene in plasma than in breast milk, whereas xanthophylls, such as lutein and zeaxanthin, are proportionally more prevalent in breast milk. More importantly, red palm oil supplementation increases the milk concentrations of provitamin A carotenes without decreasing the milk concentrations of xanthophylls. In summary, this study demonstrates that a regulated uptake of polar carotenoids into breast milk exists and that supplementation with - and ß-carotene does not negatively affect this transfer. The mechanisms behind this transport are not fully understood and merit further study.

KEY WORDS: • ß-carotene • lutein • lactation • breast milk • red palm oil

Breast milk from healthy, well-nourished women provides the infant with all of its nutritional requirements in early life. Investigation of its composition can provide information relevant to infant and maternal nutritional requirements during lactation. The provitamin A carotenoids (ß-carotene, -carotene, and ß-cryptoxanthin) provide a significant source of vitamin A for the nursing infant (1,2). Furthermore, other carotenoids such as lutein, zeaxanthin, and lycopene identified in breast milk with no provitamin A activity have been associated with health benefits (3). Lutein and zeaxanthin are the only dietary carotenoids reported to be present in the macular pigment and may protect photoreceptors against light-initiated oxidative damage (4,5). Lower risk for macular degeneration has been associated with the consumption of food sources rich in dietary lutein (4). Furthermore, lutein supplementation as well as increased dietary intake of lutein-containing foods resulted in elevated macular pigment optical density and a reduction in damaging blue light reaching the photoreceptors (6,7). Human milk is the main source of lutein and zeaxanthin for infants until weaning occurs, and these carotenoids may also be important as protective factors in retinal pigment epithelium of the newborn infant (8,9). However, breast milk carotenoid concentrations vary greatly among countries, and patterns of breast milk carotenoids are unique to each country and reflect the dietary carotenoid supply (10). Furthermore, milk carotenoid concentrations decrease with the progression of lactation, whereas total lipids increase, indicating that the transfer of these lipophilic compounds is not merely secondary to lipid secretion into milk but is regulated by a specific transport mechanism (11). More importantly, the magnitude of reduction in milk carotenoid concentration was found to be dependent on the polarity of the carotenoid, leading to a change in carotenoid profile during lactation (12). This is indicated by a change from a higher proportion of less polar carotenoids, such as ß-carotene, in colostrum to the polar carotenoids, such as lutein and zeaxanthin, in mature milk. Currently, there is limited information on how maternal supplementation with provitamin A carotenoids might influence the carotenoid pattern in breast milk during lactation. This study was designed to investigate the effect of maternal red palm oil supplementation on differences in the carotenoid pattern between plasma and breast milk at 2 stages in lactation (1 and 3 mo postpartum) and thereby elucidate possible changes in the transfer of carotenoids from plasma to milk under different dietary treatments. Red palm oil was chosen as the supplementation vehicle because it is the richest natural source of provitamin A carotene (13), and provides oil that promotes the absorption of carotenoids.

	SUBJECTS AND METHODS

TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
    Study area and subjects. The study was conducted in the Singida rural district in central Tanzania, where the majority of mothers (74%) breast-feed their children for >18 mo (14). Pregnant women (n = 60) in their 3rd trimester, aged 18–45 y, were recruited for this study from 2 different villages as part of a red palm oil intervention study (2). All women were invited to join the study when they were seen in the antenatal clinics, provided they fulfilled the study criteria. The dietary patterns, population structure, and ecology of the 2 study villages were comparable (15). Women who were recruited in each study group were matched with respect to parity and age (Table 1). Women were recruited simultaneously in the 2 villages at the beginning of the dry season between June and August of the same year. There were no significant differences between villages in infant birth date (July–December). Women were not enrolled in the study if they were severely anemic (hemoglobin <70 g/L) or if they had severe clinical infections such as tuberculosis or HIV-related diseases as determined by interview.

    Intervention. The two study groups were as follows: 1) women in a control group (n = 30) who were encouraged to maintain their consumption of dark green leafy vegetables (DGLV)³ and in addition were given 4 kg rice/mo (a modest amount designed as an incentive rather than a dietary supplement) and 2) women in a red palm oil group (n =30) who were advised to maintain the consumption of DGLV and were given red palm oil. Red palm oil was provided monthly, throughout the 3rd trimester and the first 3 mo postpartum. Women were advised to consume 4 plastic tablespoons of oil (12 g) each day, equivalent to 2 mg of provitamin A carotenoids (Table 2). Women were encouraged to incorporate the oil into local recipes and advised not to heat the oil for too long. Red palm oil was analyzed according to Lietz and Henry (16). Information on the frequency of dietary intake during the 3rd trimester, and 1 and 3 mo postpartum was obtained by administering a modified questionnaire developed by Helen Keller International (15).

    Materials. Red palm oil was provided by the Palm Oil Research Institute of Malaysia (PORIM) as the cooking oil "Carotino." Rice was purchased on the market in Singida town, Tanzania. Pyrogallol, ascorbic acid, and BHT were from Sigma Chemicals. All other reagents and adsorbents were of analytical grade and were purchased from Merck; - and ß-carotene were purchased from Sigma Chemicals; trans-ß-apo-10'-carotenal for the synthesis of the internal standard trans-ß-apo-10'-carotenal oxime, lutein, and zeaxanthin were a kind gift from Hoffman-La Roche. HPLC accessories (PEEK tubing, PEEK frits, and HPLC columns) were purchased from Alltech and Phenomenex.

    Determination of milk fat. Milk fat was determined by measurement of glycerol released by enzymatic hydrolysis of triacylglycerols using a diagnostic kit TRIG UNIMATE 5 (Hoffman La Roche). A COBAS BIO centrifugal autoanalyzer (Roche Diagnostics) was used for the measurement of glycerol released by enzymatic hydrolysis of triacylglycerols. Milk sample preparation for the automated analyses was done according to Lucas et al. (17). The CV for within and between assays was 1.4 and 4.1%, respectively.

    HPLC analysis of plasma carotenoids. The HPLC system from Shimadzu comprised 2 LC-10AS delivery pumps, a SCL-10Avp system controller, an SIL-10Dvp autoinjector, a SPD-10Avp UV/VIS detector, and a Shimadzu CLASS VP software system for data acquisition. The mobile phase was degassed using the vacuum degasser CSI6150. The column system, column temperature, and mobile phase were as described by Hart and Scott (18), except for the omission of BHT from the mobile phase. Samples were injected via the SIL-10Dvp autoinjector with a volume of 20 µL per sample, and were held at 15°C in sealed vials to avoid evaporation and degradation. Peak response of the carotenoids was measured at 450 nm. The extraction procedure was as described by Lietz et al. (2). The within-assay CV for -carotene, ß-carotene, lutein, and zeaxanthin was 5.8, 5.8, 3.0, and 4.6%, respectively, and the between-assay CV for these analytes was 13.9, 14.7, 13.7, and 15.4%, respectively.

    HPLC analysis of milk carotenoids. The HPLC system consisted of a dual piston solvent delivery pump (Waters 600 pump), a system controller (Waters 600 Controller), a photodiode array detector (Waters 996PDA), and a Millenium software system for data acquisition (Waters Millenium version 2010). The column system, column temperature, and mobile phase were as described by Hart and Scott (18), except for the omission of BHT from the mobile phase. Samples were injected manually via a Rheodyne injection valve (Rheodyne injector No. 7125), with a volume of 20 µL/sample. Peak response of the carotenoids was measured at 450 nm. The extraction procedure was as described by Lietz et al. (2). The within-assay CV for -carotene, ß-carotene, lutein, and zeaxanthin was 5.2, 3.5, 4.4, and 4.6%, respectively, and the between-assay CV for these analytes was 15.7, 16.7, 14.6, and 16.0%, respectively.

Carotenoids in milk were expressed per volume (µmol/L) and per gram of milk fat (nmol/g). Potential variations related to differences in milk fat content of individual samples are therefore removed.

    Data analysis. Data were double-entered into spreadsheets and cross-checked. The data were used for standard descriptive statistics and for more complex analyses using SPSS 12 for Windows®. Plasma and milk carotenoids were log normally distributed; thus analyses were conducted on log-transformed data and geometric means and 95% CI are presented. Differences in plasma carotenoids between treatment groups at baseline were assessed by two-tailed independent sample t test. The absolute difference between treatment groups at 1 and 3 mo postpartum was assessed by analysis of covariance with the use of the general linear model procedure, and the baseline measurement as a covariate. Two-tailed paired student's t tests were performed to test for differences within treatment groups over time. Differences were considered significant at P < 0.05.

	RESULTS

TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 
Characteristics of the study subjects are given in Table 1. Age, parity, years between pregnancy, height and weight did not differ significantly between the groups. A total of 56 mothers completed the study. Four volunteers were excluded from the study for the following reasons: neonatal death (1 volunteer), not using the red palm oil (1 volunteer) and moving to another village (2 volunteers). Data points from a few of the individuals in the study groups were not recorded or were missing due to insufficient sample amounts, thus accounting for the different sample numbers in Tables 1, 5 and 6.

Plasma zeaxanthin concentrations were significantly reduced by 30% (P < 0.01) in both treatment and control group during the course of lactation (Table 5). Unlike lutein, breast milk zeaxanthin concentrations, expressed per gram of milk lipid, were not affected in either treatment group from 1 to 3 mo postpartum (Table 6).

Plasma - and ß-carotene concentrations declined by 75% for -carotene (P < 0.01) and by 60% for ß-carotene (P < 0.001) during lactation in the control group (Table 5). However, in response to red palm oil supplementation, plasma - and ß-carotene concentrations increased (P < 0.001) by 34 and 1.8 times, respectively, from baseline to 3 mo postpartum in the red palm oil group (Table 5). As a consequence, breast milk - and ß-carotene concentrations in the red palm oil group differed (P < 0.001) from those of the control group at both 1 and 3 mo postpartum (Table 6). However, breast milk - and ß-carotene concentrations in the red palm oil group did not increase during the lactation period even after correction for milk fat content (Table 6).

Plasma and milk carotenoid concentrations in the current investigation were comparable with published data, with the exception of lutein (1,3,10,12,20–22). Plasma lutein concentrations at baseline were above the 99th percentile of plasma lutein concentrations in American women of the same age group (23). During lactation, these very high concentrations dropped by 50% and were comparable to the 95th–99th percentile of plasma lutein concentrations in American women of the same age group (23). Breast milk lutein concentrations were 9 times higher compared with women from Western societies and 3 times higher than in women from Chile, China, and Japan (10,11,20,21).

The between-subject CV for breast milk lutein and zeaxanthin was only 24% in this study. On the other hand, the between-subject CV for breast milk - and ß-carotene was 46 and 54%, respectively.

Carotenoid concentrations were always lower in breast milk than in plasma. The breast milk:plasma ratio was dramatically different depending on the polarity of the carotenoid. The - and ß-carotene concentrations were generally 88% lower in breast milk than in plasma. In contrast to the hydrocarbon carotenoids, the polar carotenoids lutein and zeaxanthin were only 68% lower in breast milk compared with plasma concentrations. The differences in proportions of these carotenoids between breast milk and plasma are indicated in Figure 1.

View larger version (17K): [in this window] [in a new window]   FIGURE 1  Proportions of lutein, zeaxanthin, -carotene, and ß-carotene in samples of plasma and breast milk of Tanzanian women that did (R) or did not (C) receive supplemental red palm oil obtained simultaneously at 1 mo (A) and 3 mo (B) postpartum. In each graph, the dashed line indicates equal proportions of carotenoids in milk and plasma. n = 25–28/treatment group.

	DISCUSSION

TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

Results from this study are in agreement with earlier studies suggesting that polar carotenoids such as lutein and zeaxanthin may be secreted into milk rather than being acquired by passive diffusion (11,12,24). To our knowledge, the first study to report that lutein is secreted into milk in preference to ß-carotene was the study by Kon and Mawson (24) in which 13 blood plasma and milk samples were obtained simultaneously. To date, only 6 other published studies have collected plasma and breast milk samples simultaneously and analyzed both hydrocarbon and xanthophyll carotenoids of mothers living in Germany, Honduras. and the United States (1,3,12,20–22). The data from our study confirm the results from these studies showing that proportionally more hydrocarbon carotenoids such as - and ß-carotene are found in plasma than in milk, whereas xanthophylls such as lutein and zeaxanthin are found in higher proportions in breast milk than in plasma (Fig. 1).

More importantly, the current investigation shows that red palm oil supplementation increased both plasma and breast milk - and ß-carotene concentrations, but did not reduce the transfer of xanthophylls into breast milk (Table 5 and 6). Indeed, the same concentrations of milk lutein and zeaxanthin were observed in women in both treatment groups. This observation is supported by 2 previous studies (1,22) in which breast milk lutein concentrations did not decline over the study period despite the change in carotenoid pattern due to ß-carotene supplementation. Because induced changes in plasma carotenoid pattern through supplementation did not change breast milk xanthophyll concentrations, this observation is the strongest indication that lutein and zeaxanthin are actively secreted into breast milk and not simply acquired by passive diffusion.

The results of the current study, in agreement with those of Schweigert et al. (12), also indicate that the uptake of xanthophylls into breast milk may be influenced by the progression of lactation (Fig. 2). Moreover, women in the red palm oil group exhibited a higher proportion of xanthophylls in milk than in plasma compared with women from the control group at both time points, suggesting that the transport mechanisms of these carotenoids are not overlapping or competing (Figs. 1 and 2).

View larger version (9K): [in this window] [in a new window]   FIGURE 2  Proportions of lutein and ß-carotene in samples of plasma and breast milk at different lactation stages. Each data point represents the mean obtained from treatment groups in this study in comparison with the study of Schweigert et al. (12). In each graph, the dashed line indicates equal proportions of carotenoids in milk and plasma. , Red palm oil group (1 mo); , Red palm oil group (3 mo); , Control group (1 mo); , Control group (3 mo); , Schweigert et al. (12) (d 2); •, Schweigert et al. (12) (d 19).

Although the exact mechanism of transfer remains to be elucidated, evidence is accumulating to suggest that the differences in carotenoid pattern between plasma and breast milk could be related to the distribution of carotenoids within plasma lipoproteins. Hydrocarbon carotenoids exists exclusively in the hydrophobic core of lipoproteins, whereas carotenoids with polar functional groups exist at least partly at the surface (12,27). This orientation can affect the transfer of carotenoids such as lutein and zeaxanthin to other lipoproteins during circulation or uptake by extrahepatic tissue due to lipoprotein lipase (LPL) activity (27,28). LPL acts by hydrolyzing triglycerides in the inner core of chylomicrons, leading to the formation of excess surface coat folds, which can then pinch off to form discoidal HDL (29). Polar carotenoids such as lutein may be incorporated into HDL before they reach the liver, which would speed up their plasma appearance and clearance compared with the nonpolar carotenoids. Furthermore, there is competition between lutein and ß-carotene associated with their appearance in the chylomicron fraction, suggesting that these carotenoids compete for intestinal absorption, for incorporation into the chylomicron, or both (30,31).

It is interesting to note that plasma carotenoid concentrations decreased significantly from the 3rd trimester to 1 mo postpartum in this study. Schweigert et al. (12) also observed a significant decrease in plasma lutein, zeaxanthin, ß-cryptoxanthin, and 9-cis-ß-carotene from 2 to 19 d postpartum. The authors further observed a significant decrease in plasma triacylglycerol, phospholipids, and -tocopherol concentrations and attributed this to a decrease in plasma lipoproteins because the distribution of carotenoids among the lipoprotein fractions did not change with the stage of lactation (12). Lutein and zeaxanthin are distributed equally between the HDL and the VLDL/LDL lipoprotein fractions, whereas the less polar carotenoids are associated predominantly with the VLDL/LDL fractions (12,27). Although the distribution of carotenoids among the plasma lipoprotein fractions does not change with the stage of lactation, the carotenoid pattern in milk differs significantly between colostrum and mature milk, indicating a change from a higher proportion of the less polar carotenoids, - and ß-carotene, in colostrum to the polar lutein and zeaxanthin in mature milk (11,12). It is therefore possible that a selective uptake of HDL might be responsible for the change in carotenoid pattern in breast milk compared with plasma. The scavenger receptor class B type I (SR-BI) mediates cellular uptake of HDL because the HDL apolipoproteins (apoA-I, apoA-II, and apoC-III) bind to SR-BI with high affinity (32). It is not known whether mammary epithelial cells express members of the scavenger receptor class B type, but SR-BI mRNA and protein were found in the mammary gland of pregnant rats (33). Furthermore, it was shown that SR-BI is involved in the transport of lutein (34).

Another explanation for the change in carotenoid pattern in milk during the lactation period could be related to the activity of mammary lipoprotein lipase (LPL). During lactation, an increase in mammary LPL activity and a decrease in adipose tissue LPL activity lead to an increased catabolism of lipoprotein and chylomicron particles at the mammary gland (35). Lipophilic substances such as retinol and -tocopherol are taken up into the mammary gland through the mediation of the binding of chylomicrons to LPL and the lipolytic process (36,37). On the other hand, it is possible that increased catabolism of chylomicron particles increases the formation of discoidal HDL, which are then catabolized directly by the endothelial lipase. This lipase is a key enzyme in HDL metabolism and was recently identified in the mammary gland (38).

The strongest biological evidence for a selective tissue uptake of lutein and zeaxanthin is the concentration of these carotenoids in the macular pigment (1 mmol/L), which is 500-fold higher than the concentration in other tissues (2 µmol/L) (4). There is evidence to suggest that this accumulation of xanthophylls in the retina is related to retinal tubulin, a major carotenoid-binding protein (39). The discovery of specific lutein-binding proteins in the midgut of the silkworm Bombyx mori suggests that these proteins might also occur in tissues other than the macular (40). To date, none have been identified in the mammary gland.

In summary, this study suggests that there is regulated uptake of polar carotenoids into breast milk and that supplementation with - and ß-carotene does not negatively affect this transfer. High intakes of dietary - and ß-carotene will not diminish breast milk lutein concentrations. The mechanisms behind this transport are not fully understood and merit further study.

	ACKNOWLEDGMENTS

 
We are grateful to M. Mseke, D. Majige, A. S. Mngale, and J. Kaganda (Tanzania Food and Nutrition Centre) for their help with recruitment and field work; to E. Olomi (Regional Agriculture and Livestock Development Officer for Singida), and H. Mlay (District Medical Officer for Singida Rural District), for their assistance; and to A. Juma, P. Kihwele, and A. Rashidi from the Tanzanian Food and Nutrition Centre for their support of the technical work. We also gratefully acknowledge the statistical advice given by Robert Shiel.

	FOOTNOTES

 
¹ Funded through grants by the Department for International Development (DFID), Palm Oil Research Institute Malaysia (PORIM), Parkes Foundation, British Nutrition Foundation and Centre for International Child Health (CICH), London. Further support was given by the International Foundation for Science (IFS), Sweden, International Program in Chemical Science (IPCS), Uppsala University, Sweden, and the Tanzania Food and Nutrition Centre (TFNC).

³ Abbreviations used: DGLV, dark green leafy vegetables; LPL, lipoprotein lipase; SR-BI, scavenger receptor class B type I.

Manuscript received 19 December 2005. Initial review completed 13 January 2006. Revision accepted 10 April 2006.

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TOP ABSTRACT SUBJECTS AND METHODS RESULTS DISCUSSION LITERATURE CITED

 

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