Bioavailability

Label ≠ absorbed

Bioavailability, explained simply

How much of a nutrient you actually absorb and use. Of 18 mg of iron in food, the body may absorb under 1 mg or several milligrams, depending on the form and its stores.

Examples

Heme iron (meat) ~15–35% absorbed vs non-heme iron (plants) ~2–20%. Calcium from spinach is poorly absorbed due to oxalate. Lycopene from cooked tomatoes is more available than raw.

Why it matters

Comparing foods by label numbers alone can mislead.

Evidence & sources

• Heme iron has higher bioavailability than non-heme iron. Evidence: established. Known: Well established. Unknown: Absorption also depends on iron status. Source: NIH Office of Dietary Supplements, Iron — Health Professional Fact Sheet (Current revision).

Connected topics

• Absorption
• Iron
• Calcium
• Spinach
• Tomato
• Vitamin C

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General education only, not medical advice. Drafted Oct 2026 · pending qualified expert review.