Swedish Toddler Study Traces Toxic Metals in Blood Back to Everyday Foods

A nationwide Swedish study has mapped, with unusual precision, exactly which foods deliver toxic metals and essential trace elements into the bodies of toddlers and preschool children. By combining detailed two-day food diaries with sensitive measurements of metals in blood and urine, researchers found that seafood drives exposure to organic arsenic compounds and methylmercury, plant-based meat and milk alternatives along with nuts and seeds raise cadmium burdens, and vegetables appear to be a previously underappreciated source of low-level inorganic arsenic. The good news is that biomarker concentrations of toxic metals in the nearly 600 children studied were generally low. The troubling news is that roughly half of the children appeared to have suboptimal selenium status, a nutrient that helps the body defend itself against metal toxicity.

The study, published in the Journal of Exposure Science and Environmental Epidemiology, drew on Riksmaten Young Children, a national dietary survey conducted by the Swedish Food Agency between 2021 and 2023. A register-based random sample of families across Sweden completed a web-based food diary covering two non-consecutive days, and a subsample living near seven regional occupational and environmental medicine clinics also provided blood and urine samples. The final analysis included 305 children aged 1.5 years and 288 children aged 4 years. Guardians recorded everything their children ate from a database of 1,218 food items, and statistical modeling converted those two days of recall into estimates of habitual long-term consumption in grams per day.

The analytical machinery behind the exposure measurements was considerable. Whole blood and urine concentrations of arsenic, cadmium, cobalt, mercury, lead, copper, manganese, selenium, and zinc were quantified using inductively coupled plasma mass spectrometry, a technique that ionizes samples in a plasma torch and reads out elemental signatures with parts-per-trillion sensitivity. Arsenic speciation demanded an extra layer of sophistication: high-performance liquid chromatography separated arsenobetaine, the harmless organic form abundant in marine fish, from the metabolites of inorganic arsenic, the genuinely toxic form. Urinary fluoride was measured with an ion-specific electrode, and all urinary concentrations were adjusted for dilution using specific gravity. The team even ran an overnight leaching test on the blood collection tubes to confirm the containers themselves were not contaminating the samples.

What emerged was a picture of exposure shaped less by any single food than by the overall architecture of a child’s diet. The researchers used two complementary statistical approaches. Principal component analysis asked which combinations of foods tend to be eaten together, while k-means clustering sorted children into mutually exclusive dietary profiles. Both methods converged on the same story. A dietary pattern rich in vegetables, fruits and berries, and fish and seafood was positively associated with blood arsenic, dominated by arsenobetaine, as well as blood mercury, mainly methylmercury, and blood selenium at both ages. Children eating a western-style diet of meat, cereals, and sweets showed lower selenium than those with a high-diversity diet.

The arsenic findings required careful chemical detective work. Seafood is loaded with arsenosugars and arsenolipids that the body converts to dimethylarsinic acid, or DMA, which can inflate apparent inorganic arsenic exposure. To disentangle this, the researchers restricted part of their analysis to children whose urine contained less than 80 percent DMA, since populations exposed to true inorganic arsenic typically excrete 60 to 80 percent of it as DMA. In that restricted group of 188 four-year-olds, the correlation between urinary inorganic arsenic metabolites and seafood faded away, but the correlation with vegetable consumption remained essentially unchanged. Median inorganic arsenic metabolite concentrations in these children were just 3.6 micrograms per liter, well below the 6.4 micrograms per liter reported for American children in national survey data, suggesting that inorganic arsenic exposure in young Swedes is low but that vegetables contribute measurably to it.

Mercury told a more familiar story. Blood mercury, which in Sweden comes almost entirely from methylmercury in fish, correlated with seafood consumption at both ages, and children who ate canned tuna had slightly higher blood mercury than those who did not. The median blood mercury concentration of about 0.99 micrograms per liter was higher than in Greek, Canadian, and American children of comparable ages, yet remained far below the United States health-based guidance value of 5.8 micrograms per liter. Intriguingly, blood mercury also correlated with vegetable intake, but the researchers suspect this reflects the tight dietary coupling of fish and vegetables in health-conscious families rather than meaningful mercury content in produce itself.

The cadmium results may be the most timely. Among the youngest children, adherence to a dietary pattern dominated by plant-based meat and milk alternatives, nuts, and seeds was associated with higher urinary cadmium, and children in the plant-based cluster had higher urinary cadmium than peers on high-diversity or western-style diets. The explanation likely lies in plant physiology: legumes such as soy and pea, the building blocks of most meat alternatives, readily take up cadmium from soil. Swedish market basket data show mean cadmium concentrations of 11 micrograms per kilogram in meat alternatives versus 1.3 in traditional meat. Phytate in nuts and seeds can bind cadmium and reduce its absorption, and lower iron status in children avoiding meat may further enhance gastrointestinal cadmium uptake, a phenomenon documented in Swedish adolescents.

Fluoride exposure followed geography and water source more than diet. The highest urinary fluoride concentrations appeared in children living around Uppsala, where public drinking water naturally carries elevated fluoride, and well water consumption predicted higher urinary fluoride than public water, especially among four-year-olds. In southeastern Sweden, nearly a quarter of roughly 4,800 private wells exceeded the World Health Organization guideline of 1.5 milligrams per liter. The researchers also speculate that fluoride in tap water used to dilute juice concentrates may contribute, and that swallowed toothpaste, which typically contains about 1,000 micrograms of fluoride per gram, adds another pathway in small children.

Perhaps the most consequential finding concerns selenium, an essential cofactor for antioxidant enzymes that may also buffer the toxicity of methylmercury. Median blood selenium was 103 micrograms per liter at both ages, hovering at the threshold below which plasma concentrations are considered to reflect deficiency based on glutathione peroxidase activity. Seafood, nuts, seeds, and legumes emerged as the main dietary protectors, with children on plant-based diets achieving selenium levels comparable to those on high-diversity diets. The suboptimal status of so many children is attributed to the notoriously selenium-poor soils of Sweden and the broader Nordic region, a geological constraint that no dietary pattern fully overcomes.

The authors are careful about the limits of their cross-sectional design, which cannot establish causality, and about the modest urine sample availability among the youngest children. Still, the dual statistical framework, the national representativeness, and the rigorous speciation chemistry make this one of the most complete portraits to date of how everyday foods translate into metal exposures in early childhood. The practical takeaway is not that parents should strip seafood, vegetables, or plant-based alternatives from the menu, since these foods also carried the benefits of better selenium status and overall diet quality. Rather, the study signals a need for closer scrutiny of cadmium in plant-based products and inorganic arsenic in vegetables, and it gives regulators a data-driven map of where the next generation’s chemical exposure actually begins: on the toddler’s plate.

Subject of Research: Dietary sources and patterns of toxic metal and essential trace element exposure in Swedish young children

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

Article References: Islam, M. R., Trask, M., Kampouri, M., Levi, M., Singh, T., Gustin, K., Bjermo, H., Almerud, P., Harari, F., Vahter, M., Lignell, S., & Kippler, M. (2026). Identifying dietary sources and patterns of exposure to toxic metals and other trace elements in Swedish toddlers and young children. Journal of Exposure Science & Environmental Epidemiology. https://doi.org/10.1038/s41370-026-00973-5

Image Credits: AI Generated

DOI: 10.1038/s41370-026-00973-5

Keywords: toxic metals, arsenic, cadmium, methylmercury, selenium, children's diet, biomonitoring, plant-based alternatives, seafood, vegetables, fluoride, Sweden