Spinach: what's on the label, and what the studies found gets in
As audited on 2026-10-17, counted eaten alone, from zero: Spinach lists a lot. In the studies, little of it gets in: its calcium and iron barely get through, and vitamin E and K do better with some fat on the plate.
Checked against its sources, in English and French, on 2026-10-17, with data v0.2. The text is as audited; any figure that comes from the live database is recomputed when the page loads and must still match it.
Audited with data v0.2 and method v0.2. The site is now on data v0.6, method v0.4.
Still holds: The studies, surveys and limits it cites, and every figure bound to the live data: those are recomputed when the page loads and must still match, or this page would not show.
What has moved: Since 18 October the food pages count grams to a limit from the room left after an average adult’s intake, so their gram figures are smaller than this card’s, which count from zero. The card is as audited; see the correction of 18 October.
One food, five nutrients, five different kinds of measurement. Read each line on its own.
| Nutrient (85 g raw on the label) | What was measured | Result | Tested how |
|---|---|---|---|
| Calcium (57 mg) | share of the calcium absorbed | 5% (about 3 mg) | 200 mg of spinach calcium, 13 adults ⚑ |
| Iron (0.9 mg) | share of iron added to spinach purée that was absorbed | 1.4% | 3 mg of iron salt stirred into 100 g of cooked purée, 7 women; scaled to a standard reference ◆ |
| Magnesium (79 mg) | share of magnesium absorbed from a meal with spinach | 27% (36.5% with kale instead) | 300 g of cooked spinach with bread, 8–9 adults ◇ |
| Vitamin E (1.7 mg) | share of the vitamin E absorbed (a minimum estimate) | 2.4% alone; 4.9% with a hard-boiled egg | about 118 g of microwaved spinach, 8 adults ◇ |
| Vitamin K (410 µg) | absorbed relative to a vitamin K supplement | 4% alone; 13% with 25 g of butter | 227 g of boiled spinach, 5 adults ◇ |
What comes with it
| Per 85 g | What it means | |
|---|---|---|
| Oxalate | (not listed) | About 2–5% of spinach's oxalate shows up in urine, in three small human studies. It matters for people prone to calcium-oxalate kidney stones |
| Cadmium | 9.2 µg | It takes about 1,620 g a week, eaten alone, to reach EFSA's limit (70 kg adult) |
- Calcium: Heaney, Weaver & Recker 1988. ⚑ The test dose was 3.5 times one serving's calcium; smaller doses are usually absorbed a little better.
- ◆ Iron: this measures what spinach does to iron mixed into it (Gillooly 1983), not the absorption of spinach's own iron, which no human study we could read reports. The same study blames spinach's polyphenols, not its oxalate. Every person's figure was scaled to a standard 40% absorption of a reference iron dose, so the 1.4% is a comparison figure.
- Magnesium: a whole-meal figure (Bohn 2004), not spinach alone; the kale meal is the same study's comparison.
- Vitamin E: Rezaei 2026. The egg had to be eaten with the spinach: in a five-person follow-up, an egg three hours later gave no gain.
- Vitamin K: relative to a supplement, not a share of the dose (Gijsbers 1996). In another study, 150 g of raw spinach gave about 17% of a 500 µg tablet's response (Garber 1999, 3 people).
- ◇ The study tested cooked or microwaved spinach; the label amounts are raw spinach (USDA FoodData Central).
- Every result is grade A (a human study of spinach); every label amount is grade C (a database value). Small studies: 5 to 13 people each.
- Not on this card: folate (two human studies disagree, 30% vs 81% relative to folic acid), beta-carotene and vitamin A conversion (three studies, 9 to 21 parts beta-carotene per part vitamin A).
Foodtopsy · audit dated 2026-10-17, on dataset v0.2 and method v0.2 · sources and corrections: the receipt below · corrections · Information, not medical advice.
Where each number comes from
Where every figure on the card comes from.
Listed values (per 100 g → per 85 g, Health Canada V.1): USDA FoodData Central, Foundation 1999633 "Spinach, mature" (8 samples): calcium 66.64 mg → 56.6; iron 1.054 mg → 0.90; magnesium 92.96 mg → 79.0. SR Legacy 168462 "Spinach, raw" (no Foundation value): vitamin E (alpha-tocopherol) 2.03 mg → 1.73 (7 data points); vitamin K (phylloquinone) 482.9 µg → 410 (1 data point). Folate 113.4 µg (Foundation) is listed but not on the face.
Calcium
- Study · measure · n · population
- Heaney, Weaver & Recker 1988, Am J Clin Nutr 47:707, PMID 3354496 · fractional absorption (double isotope) · 13 · healthy adults
- Figure as printed
- 5.1% (same-study milk 27.6%)
- Test dose / meal · preparation · access
- 200 mg Ca labelled with ⁴⁵Ca · preparation not stated in the abstract · abstract
- Also in the receipt
- Absorbed: 56.6 × 0.051 = 2.9 mg (card 1's figure). Weaver & Heaney 1991 (PMID 1760767): 2.9% at 200–300 mg, n 14. Grusak & Abrams (USDA-ARS record): about 3% in 13 teenagers, cooked and puréed
Iron
- Study · measure · n · population
- Gillooly et al. 1983, Br J Nutr 49:331, doi:10.1079/bjn19830042 · fraction of added iron absorbed (radioiron, red-cell incorporation), geometric mean · 7 · parous Indian women near Durban (iron deficiency common in that community)
- Figure as printed
- 0.014 (±1 SD range 0.006–0.032)
- Test dose / meal · preparation · access
- 3 mg Fe as labelled FeSO₄ stirred into 100 g of puréed spinach (boiled 20 min in salted water), fasting · full text (Table 3 read from the page image)
- Also in the receipt
- Every individual result adjusted to a 0.40 reference-salt absorption (3 mg Fe as ferrous ascorbate; this group's reference geometric mean was 0.271). Authors: across the vegetables, absorption fell as total polyphenols rose (inverse correlation, r 0.859); they point to polyphenols, not oxalate. The study's own iron in spinach: not measured
Iron (context)
- Study · measure · n · population
- Storcksdieck genannt Bonsmann et al. 2008, Eur J Clin Nutr 62:336, PMID 17440529 · stable-isotope iron absorption from wheat rolls with 150 g spinach or kale · 16 women (13 completed both studies)
- Figure as printed
- spinach meal 24% lower than the kale meal (not significant); oxalate added to kale did not change absorption
- Test dose / meal · preparation · access
- abstract
- Also in the receipt
- "Our findings strongly suggest that OA in fruits and vegetables is of minor relevance in iron nutrition." No spinach-meal percentage in the abstract
Magnesium
- Study · measure · n · population
- Bohn et al. 2004, Br J Nutr, PMID 15035687 · apparent absorption (²⁵Mg extrinsic label, faecal monitoring) · 9 (8 or 9 evaluated; unresolved in the paper) · healthy adults, mean age 23
- Figure as printed
- 26.7% (SD 10.4); kale meal 36.5% (SD 11.8)
- Test dose / meal · preparation · access
- 100 g phytate-free white bread + 300 g spinach (frozen, cooked, puréed), 121 mg total Mg in the meal, two portions at breakfast and lunch · full text
- Also in the receipt
- A meal-level figure: the label covers bread and vegetable together. Listing is raw, study cooked (◇)
Vitamin E
- Study · measure · n · population
- Rezaei et al. 2026, PMID 42792114 · fractional absorption, plasma-based minimum estimate (intrinsic deuterium label) · 8 · healthy adults 18–65
- Figure as printed
- spinach alone 2.39% ± 0.60; with 1 hard-boiled egg 4.93%; 2 eggs 3.99%; 3 eggs 4.41%; egg whites 4.07%; 9.6 g soybean oil 4.91%
- Test dose / meal · preparation · access
- about 118 g labelled spinach (5 mg d-α-tocopherol), chopped, microwaved, frozen, microwaved again · full text
- Also in the receipt
- Sub-study (n 5): spinach alone 1.96%, egg at 0 h 4.47%, egg 3 h later 1.63% ("enhancement… requires concurrent co-ingestion"). Arm rule (decided 2026-10-17): the face shows the spinach-alone arm and the one-egg arm; the rest stay here
Vitamin K
- Study · measure · n · population
- Gijsbers et al. 1996, PMID 8813897 · relative bioavailability: serum response (AUC) vs 1 mg phylloquinone as Konakion, same people · 5 · healthy non-smokers
- Figure as printed
- 4.1% (ratio of mean AUCs, 8.0 / 193.1); with 25 g butter 13.3%
- Test dose / meal · preparation · access
- 227 g deep-frozen shredded spinach heated to boiling (1 mg phylloquinone), fasted · full text
- Also in the receipt
- Individual subjects 1.9–10.9% alone. The authors' own derived figure: "less than 10%" of vegetable phylloquinone absorbed. Garber et al. 1999 (PMID 10356087): raw spinach vs a 500 µg tablet, 17.4% at 150 g (n 3), 9% at 50 g (n 4)
Oxalate (hazard side)
- Study · measure · n · population
- Brinkley et al. 1981, Urology 17:534, PMID 7245443 · urinary oxalate increase over 8 h · 8 · normal volunteers
- Figure as printed
- spinach load 1,236 mg; urinary oxalate up 29.3 mg (2.4%); spinach and chocolate 2.4–2.6% vs sodium oxalate 6.5–7.3%
- Test dose / meal · preparation · access
- a large serving of spinach · abstract
- Also in the receipt
- Derived: 29.3 ÷ 1,236 = 2.4%
Oxalate
- Study · measure · n · population
- Hanson et al. 1989, Food Chem Toxicol 27:181, PMID 2731814 · urinary oxalate over 24 h · 9 · women
- Figure as printed
- 4.5% (sodium oxalate 6.2%)
- Test dose / meal · preparation · access
- 25 g spinach providing 120 mg oxalic acid, at breakfast · abstract
- Also in the receipt
- —
Oxalate
- Study · measure · n · population
- Brogren & Savage 2003, Asia Pac J Clin Nutr 12:219, PMID 12810415 · soluble-oxalate bioavailability from urinary oxalate · 10 · volunteers
- Figure as printed
- 1.93% ± 0.85 over 24 h (0.75% over 6 h)
- Test dose / meal · preparation · access
- 100 g grilled frozen spinach · abstract
- Also in the receipt
- Sour cream and calcium-enriched milk with the spinach lowered it significantly
Cadmium
- Study · measure · n · population
- receipt card 5
- Figure as printed
- 107.8 µg/kg · 11 composites · Health Canada TDS
- Test dose / meal · preparation · access
- 9.2 µg per 85 g; 175 ÷ 0.1078 = 1,620 g a week to EFSA's TWI (70 kg)
- Also in the receipt
- Average adult already at about 71% of the limit (EFSA 2012, adult median), shown beside, not subtracted
Not on the face: folate (Hannon-Fletcher 2004: 30% relative to folic acid, n 18; Konings 2002: 81% relative, ileostomy volunteers; a 2.7-fold spread), beta-carotene (Castenmiller 1999: 5.1% relative to a supplement, whole leaf), vitamin A conversion (Wang 2007 9:1; Li 2007 10.1:1 in children; Tang 2005 20.9:1), riboflavin and vitamin B6 (single studies).