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Abstract

Children’s development and their health outcome is one of major public health concerns. Quality of the maternal diet and lifestyle before the pregnancy, during pregnancy, and the breastfeeding period have an important influence on the child’s development later in life. Exposure to potentially toxic chemical elements and nutritional status of essential elements and fatty acids (FAs) during pregnancy and the breastfeeding period are known for potential adverse development and health effects in children.
In this thesis, the exposure assessment to potentially toxic chemical elements and the nutritional status of essential elements and FAs were investigated in the primiparous mothers in different geographical areas of Slovenia. The study builds on the rich data obtained in the first national human biomonitoring study (HBM, 2007-2014), which included 535 first-time mothers.
The first objective was to investigate the relationship between the composition of FAs, their stable carbon isotopes (δ13CFA) and trace elements composition in human milk and mother’s dietary habits and living area. The underlying purpose of the first objective was to improve the understanding of the exposure to selected elements through determination of indicatory FAs and their compound-specific stable isotope signatures. For this reason, the associations between the maternal diet and FAs composition in 74 samples of mature human milk from two contrast Slovenian areas were investigated. The results of the data from questionnaires revealed statistically significant differences in the dietary intake of game, freshwater fish, and fresh and frozen seafood between the study areas. In the coastal area, despite the higher intake of fresh seafood, the levels of saturated and monounsaturated FAs were higher and the levels of polyunsaturated fatty acids (PUFAs), omega-3 (ω-3), and omega-6 (ω-6) FAs were lower compared to those in the inland Pomurje region. The ω-6/ω-3 ratio did not differ significantly between the study areas. This finding was not expected and indicates a discrepancy between the measured and self-reported data. The latter is a consequence of insufficient data information on dietary supplements, which can be an important source of essential elements and FAs. This is the first study to investigate the possibility to use stable carbon isotopes of FAs in human milk as a biomarker of seafood consumption.
Additional data evaluation using data mining approaches confirmed that using the classifier for fresh seafood intake based on the seven variables, including elemental composition, levels of FAs, and their stable isotopes in milk, enables distinguishing between lower and higher fresh seafood consumption with 84% accuracy. Clustering could be used to divide the data sets into two with 90% accuracy. A clustering approach based on the percentage of the certain FAs and δ13CFA is an accurate indicator to distinguish between higher and lower fresh seafood intake. This confirmed our hypothesis that stable carbon isotope analysis in combination with elemental analysis is an important tool to distinguish between diets, particularly for fresh seafood. These findings suggest that in human-related studies related to the risks and benefits of seafood consumption, the analyses of FAs, their stable carbon isotopes, and elemental compositions can significantly improve precision of the data on seafood consumption.
The second objective of the study was to examine the relation between the child’s birth weight and maternal blood levels of toxic and potentially toxic elements and socio-demographic characteristics and maternal dietary habits. The results of the multiple regression results of 494 Slovenian mother-child pairs from 12 different areas revealed that statistically significant (p < 0.5) and positive association between manganese (Mn) in maternal blood and birth weight. This could be explained by the essentiality of Mn in fetal development as an important cofactor in enzyme reactions in bone formation and in metabolic regulation for amino acid, lipid, protein and carbohydrate levels. Besides blood Mn levels, maternal age, pre-pregnancy body mass index, estimated gestational age at birth and gender of the child were the main predictors of the child’s birth weight.
The overall conclusion of this work was that the routine HBM studies intended for spatial and time trends exposure to potentially toxic chemicals of population can benefit greatly from additional biomarker analysis, including compound-specific carbon isotope signatures, which are useful for source apportionment of nutritional and toxic compounds. Moreover, data mining approaches may further improve data interpretation beyond classical statistical treatment of data in HBM studies.