This national total diet survey measured selenium, iodine, iron and sodium in 121 foods bought at retail and prepared as eaten, then combined the concentrations with simulated diets for eight age-sex groups. Seafood carried the highest selenium concentrations, and seafood, chicken, eggs, breads and grain products supplied most dietary selenium. Estimated mean selenium exposure for adult women was about 18% below the recommended daily intake, while no group approached the upper level.
Key numbers
- Selenium across the 121 foods ranged from below 0.002 to 0.64 mg/kg, the highest in mussels (Results, p. 617).
- Mean selenium, table-ready basis, n = 8 composites per food: mussels 0.5650 mg/kg (0.449 to 0.639); canned fish 0.5055 mg/kg; fresh grilled fish 0.4920 mg/kg; oysters 0.4115 mg/kg; boiled egg 0.2685 mg/kg; fried chicken 0.1990 mg/kg; fried lamb’s liver 0.1975 mg/kg; fried pork chop 0.1373 mg/kg; white bread 0.0354 mg/kg; whole milk (3.25% fat) 0.0066 mg/kg; white rice 0.0093 mg/kg (Table 3, pp. 618 to 619).
- Estimated mean selenium exposure: 67 µg/day (men 25 and over), 49 µg/day (women 25 and over), 71 µg/day (young men 19 to 24), 55 and 41 µg/day (boys and girls 11 to 14), 32 µg/day (children 5 to 6), 21 µg/day (toddlers 1 to 3), 16 µg/day (infants 6 to 12 months) (Table 4, p. 621).
- Reference values used: recommended daily intake 70 µg/day for adult men and 60 µg/day for adult women; upper level 400 µg/day for adults, down to 60 µg/day for infants (Table 4, p. 621).
- Women 25 and over: 49 µg/day, 18% below the recommended 60 µg/day (p. 621).
- Analytical CV for selenium across duplicates: 17%; reference-material recovery for selenium in bovine muscle as low as 69% (p. 617, Table 2).
Methods (brief)
Foods were purchased at retail, prepared table-ready, and analyzed by ICP-MS after tetramethylammonium hydroxide digestion. Detection limits ranged from 0.001 to 50 mg/kg depending on element and matrix. Non-detects were set to half the detection limit for means. Exposures combine mean concentrations with two-week simulated diets based on average energy intake.
Evidence fitness
Supports population-average dietary selenium exposure estimates for New Zealand in 2003-4 and food-level selenium concentrations on an as-eaten basis. It does not describe the distribution of individual intakes, brand-level variation, or selenium species.
Limitations
Exposure estimates reflect average consumers only; the authors note high consumers may reach about twice the average. Samples are composites. Selenium recovery from one reference material was low. New Zealand soils are low in selenium, so concentrations may not transfer to other countries.
Related evidence
- Selenium
- Molluscs
- Fish
- Eggs
- Chicken
- ICP-MS — Inductively coupled plasma mass spectrometry
- Total diet study methodology
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