cadmium (Cd) enters the human body primarily through food. Unlike nickel, which has high-concentration food categories that can be avoided, cadmium contamination is diffuse — embedded in staple crops, leafy greens, and grains that form the basis of most dietary patterns worldwide.
How Cadmium Enters the Food Supply
Cadmium reaches food through three primary routes:
Soil contamination. Phosphate fertilizers are the largest anthropogenic cadmium source in agricultural soils. Sewage sludge application, industrial emissions, and atmospheric deposition also contribute. Once in soil, cadmium has a half-life measured in decades — it accumulates over successive growing seasons [1].
Plant uptake. Cadmium enters plants through the same calcium (Ca²⁺) and zinc (Zn²⁺) transporters that absorb essential minerals. This is a key example of mis metallation — toxic metals hijacking essential metal channels. Plants cannot distinguish cadmium from calcium at the transporter level, so cadmium-contaminated soil produces cadmium-contaminated crops regardless of species [2].
Bioconcentration. Certain plant families actively concentrate cadmium above soil levels (bioconcentration factor >1.0). Leafy greens and root vegetables are particularly efficient cadmium accumulators.
Cadmium Content in Foods
The major dietary cadmium sources, ranked by contribution to total intake:
| Food Category | Cd Content Range | Notes |
|---|---|---|
| Rice | 0.01-0.40 mg/kg | Highest single-food contributor globally; paddy flooding mobilizes soil Cd |
| Leafy greens (spinach, lettuce) | 0.01-0.25 mg/kg | Hyperaccumulator crops; organic ≠ lower Cd |
| Root vegetables (carrots, potatoes) | 0.01-0.10 mg/kg | Direct soil contact increases uptake |
| Wheat and cereals | 0.01-0.08 mg/kg | Staple crop, high consumption volume |
| Chocolate/cocoa | 0.01-0.30 mg/kg | Cacao trees accumulate Cd from volcanic soils (Latin America) |
| Shellfish (oysters, mussels) | 0.05-2.0 mg/kg | Filter-feeders concentrate waterborne Cd |
| Organ meats (kidney, liver) | 0.05-1.0 mg/kg | Bioaccumulation in animal excretory organs |
| Sunflower seeds | 0.02-0.20 mg/kg | Sunflowers are known Cd hyperaccumulators |
Critical detail: Rice is the dominant global cadmium source not because it has the highest concentration per kilogram, but because of its enormous consumption volume. In Asian diets, rice can contribute 40-60% of total dietary cadmium [1].
Absorption and the Role of Nutritional Status
Cadmium absorption from the GI tract is typically 3-8% in adults, but this increases dramatically under specific conditions:
- Iron deficiency increases cadmium absorption 2-3x via upregulated DMT1 (divalent metal transporter 1) — the same transporter handles both Fe²⁺ and Cd²⁺. This is another mis metallation pathway.
- Calcium deficiency increases Cd absorption through shared calcium channels.
- Zinc deficiency reduces metallothionein production, decreasing the body's cadmium-binding capacity.
- Low protein intake reduces metallothionein synthesis.
This creates a vulnerability paradox: populations with the worst nutritional status absorb the most cadmium from identical dietary exposure.
Infant Vulnerability
Infants face disproportionate cadmium exposure through two mechanisms [3]:
Formula and baby foods. German infant formula analysis found cadmium contributed up to 178% of the Tolerable Weekly Intake (TWI) in highly exposed infants. Vegetable-based baby foods (carrots, spinach, sweet potatoes) are among the highest-cadmium commercial infant food products.
Immature detoxification. Infants have lower metallothionein expression, immature renal clearance, and higher gut absorption rates. The developmental window from 6-24 months — when solid foods are introduced — coincides with maximum vulnerability to cadmium accumulation [2].
Cadmium, Diet, and the Gut Microbiome
Dietary cadmium exposure alters gut microbial composition in ways that compound its toxicity:
- High-fat diets amplify cadmium accumulation — mice on HFD showed increased Cd retention in liver and kidney compared to normal diet controls, with corresponding dysbiotic shifts [4].
- Cadmium depletes glutathione — the primary intracellular antioxidant and cadmium detoxification molecule. Chronic low-level exposure progressively exhausts glutathione reserves.
- Cadmium and arsenic co-exposure (common in rice-based diets) produces synergistic gut microbiota disruption and liver toxicity beyond what either metal causes alone Zhang et al. 2015.
Regulatory Landscape
- EFSA TWI: 2.5 μg/kg body weight/week
- JECFA PTMI: 25 μg/kg body weight/month
- Codex Alimentarius: Maximum levels set for rice (0.4 mg/kg), wheat (0.2 mg/kg), leafy vegetables (0.2 mg/kg), cocoa products (variable by category)
- No FDA action level for cadmium in infant foods (as of 2026)
Key Sources
Connections
- cadmium — the metal entity page
- mis metallation — cadmium enters through calcium and zinc channels
- glutathione — primary cadmium detoxification molecule, depleted by chronic exposure
- heavy metals infant foods — cadmium in baby food and formula
- dietary nickel exposure — parallel dietary metal exposure pathway
- plant metal hyperaccumulation — why certain crops concentrate cadmium
- oxidative stress — cadmium-driven ROS generation via Fenton chemistry