Identifying dietary sources and patterns of exposure to toxic metals and other trace elements in Swedish toddlers and young children

Abstract Background Diet is a source of many toxic compounds, but dietary sources of toxic metal exposure in young children are largely unknown. Objective To explore dietary sources and patterns of the most commonly occurring toxic metals and key elements of antioxidant defense. Methods We studied 1.5-year-olds ( n = 305) and 4-year-olds ( n = 288) in the Swedish national dietary survey “Riksmaten Young Children”. From a 2-day web-based food diary, habitual consumption (g/day) of specific food groups was estimated using the Multiple Source Method. Dietary patterns were derived using age-specific principal component analysis (PCA) and k-means clustering. Toxic (arsenic, cadmium, cobalt, lead, mercury) and essential elements (copper, manganese, selenium, and zinc) in blood and/or urine were measured with inductively coupled plasma-mass spectrometry, arsenobetaine and inorganic arsenic metabolites [methylarsonic acid (MMA), dimethylarsinic acid (DMA) and remaining inorganic arsenic)] after separation by reversed-phase/ion exchange high-performance liquid chromatography, and fluoride with an ion-specific electrode. Results Biomarker concentrations of toxic metals varied, and blood selenium was suboptimal in many children (median: 103 µg/L at both ages). Spearman rank correlation with unsupervised hierarchical cluster analysis revealed that urinary arsenobetaine and blood arsenic, mercury, and selenium correlated positively with seafood and vegetable consumption, particularly among 4-year-olds, where seafood and vegetables clustered together. In children with <80% DMA in urine, inorganic arsenic metabolites correlated positively with vegetables. In multivariable-adjusted regression models, the PCA-derived fruits-vegetables-seafood pattern was positively associated with blood arsenic (mainly arsenobetaine) among 4-year-olds as well as mercury (mainly methylmercury) and selenium at both ages. Dietary clusters dominated by plant-based meat and milk alternatives showed higher cadmium concentrations, and clusters characterized by a western-style diet (meat, cereals, and sweets) showed lower selenium concentrations than clusters with a high-diversity diet. Significance Diet contributes to exposure to arsenic compounds, methylmercury, cadmium, and selenium in small Swedish children. Impact Concentrations of toxic metals in the blood and urine of young Swedish children were generally low, though they exhibited considerable variability. Simultaneously, around half of the children appeared to have suboptimal selenium status, a key element in antioxidant defense against metal toxicity. Diets rich in plant-based alternatives, nuts, and seeds were associated with increased cadmium exposure, while high-diversity diets rich in fruits, vegetables, and seafood were associated with increased arsenobetaine and methylmercury exposure, in combination with improved selenium status. Furthermore, after excluding the contribution of arsenic compounds from fish, low concentrations of inorganic arsenic appeared to originate from vegetable consumption.