A comprehensive narrative review covering both essential trace metals (iron, zinc, copper, manganese, chromium, molybdenum, cobalt, nickel) and non-essential contaminant metals (lead, cadmium, vanadium). For each metal, the review describes chemical properties and metabolism, body distribution, biological functions, deficiency manifestations, and toxicity. The paper provides a unified framework for understanding the dual nature of metals across the adequacy window.
Key numbers
- Iron body content: 4 to 5 g; serum reference range 55 to 176 µg/dL in men and 40 to 170 µg/dL in women (p. 3).
- Iron deficiency: approximately 30% of women and 40% of pregnant women and children under 5 years worldwide (p. 3).
- Iron overload threshold: transferrin saturation above 40% supports iron overload diagnosis; at 60 to 70%, non-transferrin-bound iron is substantially elevated, increasing risk of oxidative tissue damage (p. 4).
- Zinc body content: 2 to 3 g in adults (p. 5).
- Manganese daily adequate intake: 2.3 mg/day adult men; 1.8 mg/day adult women; 1.5 mg/day children 4-8 years; 600 µg/day children 7-12 months (FDA values) (p. 11).
- Cobalt dietary intake: 5 to 50 µg/day total; AFSSA acceptable daily intake 1.6 to 8 µg/kg per day (p. 17).
- Cobalt toxicity thresholds: 300 to 700 µg/L serum associated with reversible hematological and endocrine effects; at or above 700 to 800 µg/L, more severe neurological, reproductive, and cardiac effects (p. 17).
- Molybdenum cofactor deficiency: incidence estimated at 1 in 200,000 newborns (p. 15).
- Chromium daily intake: 10 to 40 µg/day for children up to 6 months; 35 µg/day in men; 25 µg/day in women (p. 12-13).
- Lead blood reference: WHO clinical intervention threshold at 5 µg/dL blood lead; WHO emphasizes primary prevention and no safe concentration identified for neurocognitive damage in children (p. 20).
- LOD/LOQ: not reported (review paper, no primary analytical measurements).
Methods (brief)
Narrative review. No systematic search protocol described. Covers essential metals (sections 2.1 through 2.8) and non-essential metals (section 3: lead, cadmium, vanadium). Because this is a review paper, LOD/LOQ, CRM use, and recovery data are not applicable.
Evidence fitness
This source is the principal reference for essential metal body distribution, serum reference ranges, biological function, deficiency manifestations, and toxicity profiles across the full set of essential metals reviewed on the target page. The figures for iron (serum reference ranges, overload thresholds), manganese (adequate intake values, neurotoxicity), cobalt (dietary intake ranges, toxicity thresholds), molybdenum (MoCD incidence), and chromium (daily intake, glucose tolerance factor controversy) are sourced from this paper. The source does not provide finished-food concentration data, occupational exposure datasets, or primary epidemiological data.
Limitations
Narrative review; inclusion criteria are not stated. Metal-specific sections vary in depth. The chromium section explicitly discusses the ongoing scientific controversy about chromium essentiality and the absence of a characterized glucose tolerance factor, but the conclusion that chromium essentiality in humans is not definitively proven is properly grounded in the cited literature. Lead and cadmium sections focus on toxicology rather than dietary exposure.
Related evidence
- Essential metals: deficiency, adequacy, and toxicity
- Iron
- Zinc
- Copper
- Manganese
- Cobalt
- Molybdenum
- Chromium
Update history
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