Basil and spinach: two green leaves, very different plates

Spinach has a reputation as a calcium and iron food, and the absorption trials shrink it. In a crossover trial in 13 healthy adults given the same 200 mg of calcium in one test meal, 5.1 percent was absorbed from spinach against 27.6 percent from milk, a single test run in 1988. Iron was measured in 16 women aged 18 to 45. The spinach meal gave 24 percent less iron absorption than a kale meal, a gap that did not reach statistical significance, and oxalic acid added to kale did not lower its iron absorption at all. Per 100 g, UK tables give fresh basil 250 mg of calcium and 5.5 mg of iron against 170 mg and 2.1 mg for raw spinach. That comparison flatters basil. People eat it by the tablespoon, about 3 g, while a cup of raw spinach weighs 0.88 oz (25 g). We found no study comparing the two leaves directly and no trial of basil eaten as food, so every health finding below is about spinach.

How much is actually in it

• Per 100 g in UK data, fresh basil has 250 mg calcium and 5.5 mg iron against 170 mg and 2.1 mg in raw mature spinach, while spinach has more potassium. — CoFID 2021 entries Basil, fresh (13-804) and Spinach, mature, raw (13-572) (n = 2 records) Evidence E source
  Basil 40 calories, calcium 250 mg, iron 5.50 mg, potassium 300 mg, carotene 3950 ug; spinach 25 calories, calcium 170 mg, iron 2.10 mg, potassium 500 mg, carotene 3535 ug, vitamin K1 394 ug per 3.5 oz (100 g)
• Across 8 USDA samples of baby spinach, calcium ranged from 48.2 to 92.1 mg and folate from 90.4 to 155 ug per 3.5 oz (100 g). — USDA Foundation Foods, Spinach, baby, 8 samples (n = 8 samples) Evidence E source
  Calcium mean 68.35 mg (48.2-92.1); folate 116.5 ug (90.4-155.0); beta-carotene 3400 ug (3030-4000); fiber 1.558 g (1.2-2.13) per 3.5 oz (100 g)

What a real portion looks like

• A tablespoon of raw basil (3 g) gives about 12 ug vitamin K, while a cup of raw spinach (25 g) gives about 121 ug. — USDA FNDDS Basil, raw (75109400) and Spinach, raw (72125100) (n = 2 records) Evidence E source
  Basil 414.8 ug vitamin K per 3.5 oz (100 g): 1 tbsp 3 g 12.4 ug, 1 cup 24 g 99.6 ug; spinach 482.9 ug per 3.5 oz (100 g): 1 cup 25 g 120.7 ug, salad amount 50 g

What your body absorbs

• NIH ODS notes the body absorbs only 4% to 17% as much vitamin K from spinach as from a tablet, and eating the greens with some fat helps. — general population Evidence E source
  Phylloquinone from spinach 4-17% of tablet absorption
• In a crossover RCT of 13 adults, only 5.1% of calcium was absorbed from spinach against 27.6% from milk at the same 200 mg dose. — healthy adults (n = 13) Evidence B source
  Calcium absorption 5.1% spinach vs 27.6% milk; within-subject difference 22.5 +/- 9.5% (P < 0.0001)
• In crossover RCTs of 16 women, iron absorption from a 150 g spinach meal was 24% lower than from kale, and added oxalic acid itself did not reduce absorption. — apparently healthy women aged 18-45 years (n = 16) Evidence B source
  Spinach meal -24% vs kale (not significant, P > 0.16); kale 10.7% vs kale plus 1.26 g oxalic acid 11.5% (P = 0.86)

What cooking and storage change

• In 10 volunteers eating 3.5 oz (100 g) grilled spinach, only 1.93% of its soluble oxalate reached urine over 24 hours, and sour cream with calcium-rich milk lowered that further. — volunteers (n = 10) Evidence B source
  Soluble oxalate bioavailability 0.75% (6 h) and 1.93% (24 h); significantly lower with sour cream and Calci-Trim milk (P < 0.05)
• By the USDA retention table for vegetables and vegetable products, greens boiled in covering water and drained keep about 55% of vitamin C and 60% of folate. — USDA Table of Nutrient Retention Factors, Release 6, Vegetables and Vegetable Products, method 3005 Evidence E source
  Retained: vitamin C 55%, folate 60%, thiamin 80%, potassium 85%, calcium 95%, iron 95%

What it does to your health

• In a crossover RCT of 26 adults aged 38 to 69, a meal with 220 mg nitrate from spinach lowered systolic blood pressure and pulse pressure within 210 minutes. — healthy men and women aged 38-69 years (n = 26) Evidence B source
  Lower systolic BP and pulse pressure (P < 0.001), higher large artery elasticity; diastolic BP and PWV not changed
• In 18 healthy adults, a spinach drink with 800 mg nitrate cut systolic pressure from 118 to 111 mm Hg by 300 minutes. — 11 men and 7 women, mean age 28 years (n = 18) Evidence B source
  Systolic BP 118 +/- 2 to 111 +/- 3 mm Hg at 300 min (P < 0.001); peak plasma nitrite 980 nmol/L
• In two cohorts of about 251,000 adults, moderate plant nitrate intake, around 1 cup baby spinach a day, was linked to 16% lower MASLD rates. — 53,854 Danish Diet, Cancer and Health and 197,198 UK Biobank participants (n = 251052) Evidence C source
  Pooled HR Q3 vs Q1 0.84 (95% CI 0.76-0.94)

Safety, limits and interactions

• A meta-analysis of 35 studies found spinach grown with untreated wastewater averaged 2.86 mg/kg cadmium, over 9.5 times the EU limit, while treated water removed the excess. — soils and crops in 35 studies of wastewater irrigation, 2000-2021 (n = 35 studies) Evidence C source
  Spinach pooled mean 2.86 mg/kg Cd vs EU limit 0.2-0.3 mg/kg; treated water gave levels comparable to controls

What people believe that the data does not support

• The EU refused to authorize the claim that a mix of spinach, chicory and chard leaves maintains normal blood cholesterol. — EU health claim applicants Evidence E source
  Claim status Non-authorized; 0 authorized EU claims for spinach or basil

Who this works differently for

• A systematic review of 149 reports on warfarin lists spinach among foods that call for clinician awareness in people on this anticoagulant. — people taking warfarin; 149 articles on 78 herbs, foods or supplements (n = 149 articles) Evidence D source
  78 items reported to interact; spinach named in the watch list

The bottom line

Two small crossover trials used spinach as a nitrate source and measured blood pressure over a few hours. In 26 healthy adults aged 38 to 69, a meal carrying 220 mg of nitrate from spinach lowered systolic pressure and pulse pressure within 210 minutes, and the abstract gives no size for the drop. A spinach drink with 800 mg of nitrate, a concentrated dose well above a normal serving, took systolic pressure in 18 young adults from 118 to 111 mm Hg by 300 minutes in a semi-randomized design. Both measured one dose over one afternoon. In two cohorts of about 251,000 adults, moderate plant nitrate intake, which the authors put at roughly a cup of baby spinach a day, was associated with a 16 percent lower rate of MASLD, a fatty liver disease (HR 0.84, 95% CI 0.76 to 0.94). That association covers nitrate from all plants, with spinach used only as a yardstick for the dose. Boiling greens in water that covers them and then draining keeps about 55 percent of vitamin C and 60 percent of folate by the USDA retention table, a group factor for greens dated 1975 and never measured on spinach itself. Oxalate absorption was measured directly. When 10 volunteers ate 3.5 oz (100 g) of grilled frozen spinach, 1.93 percent of its soluble oxalate reached the urine over 24 hours, and eating it with sour cream and calcium-rich milk lowered that further. Vitamin K from the leaf is poorly absorbed too. NIH says the body takes up 4 to 17 percent as much from spinach as from a tablet, and some fat eaten with the greens helps. Who should be careful. A cup of raw spinach holds about 121 micrograms of vitamin K, and a systematic review of 149 reports on warfarin names spinach among the foods clinicians should keep in mind for people on that drug. Most of those reports are case reports, and the abstract gives no rating for spinach. A tablespoon of basil gives about 12 micrograms. The one contaminant finding is narrow. Spinach irrigated with untreated wastewater averaged 2.86 mg/kg of cadmium across 35 studies, over 9.5 times the EU limit, and treated water brought levels back to those of controls, so it tells you nothing about ordinary market spinach. The EU refused a health claim that a leaf mix of spinach, chicory and chard maintains normal blood cholesterol, and neither leaf holds an authorized EU claim.

Sources

1. bspn-daily-r4-01 · food composition dataset
   Basil, fresh (13-804): Energy 40 kcal | Calcium 250 mg | Iron 5.50 mg | Potassium 300 mg | Carotene 3950 ug || Spinach, mature, raw (13-572): Energy 25 kcal | Calcium 170 mg | Iron 2.10 mg | Potassium 500 mg | Carotene 3535 ug | Folate 114 ug | Vitamin K1 394.00 ug
   CoFID 2021 (Public Health England, OGL v3.0), codes 13-804 Basil, fresh and 13-572 Spinach, mature, raw · checked 2026-09-29
2. bspn-daily-r4-02 · food composition dataset
   Spinach, baby (Foundation, 8 samples): Calcium, Ca 68.35 mg, range 48.2-92.1 | Folate, total 116.5 ug, range 90.4-155.0 | Carotene, beta 3400.0 ug, range 3030.0-4000.0 | Fiber, total dietary 1.558 g, range 1.2-2.13
   USDA FoodData Central, Foundation Foods, release 2026-04-30, Spinach, baby · checked 2026-09-29
3. bspn-daily-r4-03 · reference dataset
   Basil, raw, FNDDS 75109400, fdc_id 2709780: 1 tablespoon 3 g | 1 cup 24 g | Vitamin K (phylloquinone) 414.8 ug per 100 g || Spinach, raw, FNDDS 72125100, fdc_id 2709614: 1 cup 25 g | 1 leaf 10 g | Guideline amount in salad 50 g | Vitamin K (phylloquinone) 482.9 ug per 100 g
   USDA FNDDS (FoodData Central survey 2024-10-31), Basil, raw fdc_id 2709780 and Spinach, raw fdc_id 2709614 · checked 2026-09-29
4. bspn-daily-r4-04 · agency fact sheet
   For example, the body absorbs only 4% to 17% as much phylloquinone from spinach as from a tablet [2]. Consuming vegetables at the same time as some fat improves phylloquinone absorption from the vegetables, but the amount absorbed is still lower than that from oils.
   NIH Office of Dietary Supplements, Vitamin K Fact Sheet for Health Professionals · checked 2026-09-29
5. bspn-daily-r4-05 · randomized crossover trial
   The absorbability of calcium from spinach was compared with the absorbability of Ca from milk in 13 healthy adults in a randomized cross-over design in which the test meal of either milk or spinach had 200 mg of Ca labeled with 45Ca. ... Absorption was higher from milk in every case, with the mean absorption from milk averaging 27.6% and from spinach, 5.1%.
   Am J Clin Nutr, 1988 · checked 2026-09-29
6. bspn-daily-r4-06 · randomized crossover trial
   Sixteen apparently healthy women (18-45 years, <60 kg body weight), recruited by poster advertizing from the staff and student populations of the ETH, University and University Hospital of Zurich, Switzerland. ... After normalization for the spinach reference meal absorption, geometric mean iron absorption from wheat bread rolls with kale (10.7%) did not differ significantly from wheat rolls with kale plus 1.26 g OA added as potassium oxalate (11.5%, P=0.86). Spinach was significantly higher in calcium and polyphenols than kale and absorption from the spinach meal was 24% lower compared to the kale meal without added OA, but the difference did not reach statistical significance (P>0.16).
   Eur J Clin Nutr, 2008 · checked 2026-09-29
7. bspn-daily-r4-07 · randomized crossover trial
   When frozen convenience food is grilled there is no opportunity for the soluble oxalates to be leached out into the cooking water and discarded. ... In this experiment 10 volunteers ingested 100g grilled spinach alone or with 100g additions of cottage cheese, sour cream and sour cream with Calci-Trim milk (180 g) and finally, with 20g olive oil. ... The mean bioavailability of soluble oxalate in the grilled spinach was 0.75+/-0.48% over a 6-hour period after intake and was 1.93+/-0.85% measured over a 24-hour period. Addition of sour cream and Calci-Trim milk reduced the availability of the oxalate in the spinach significantly (P<0.05) in both the 6-hour and 24-hour collection periods.
   Asia Pac J Clin Nutr, 2003 · checked 2026-09-29
8. bspn-daily-r4-08 · reference dataset
   USDA-RETN-R6:3005 VEG,GREENS,BOILED,WATER COVER DRAIN (Vegetables and Vegetable Products): vitamin_c_mg 55% | folate_total_ug 60% | thiamin_mg 80% | potassium_mg 85% | calcium_mg 95% | iron_mg 95%
   USDA Table of Nutrient Retention Factors, Release 6 (2007), Retn_Code 3005 VEG,GREENS,BOILED,WATER COVER DRAIN · checked 2026-09-29
9. bspn-daily-r4-09 · randomized crossover trial
   Twenty-six participants aged 38-69years were recruited to a randomized controlled cross-over trial. The acute effects of two energy-matched (2000kJ) meals, administered in random order, were compared. The meals were either high nitrate (220mg of nitrate derived from spinach [spinach]) or low nitrate [control]. ... Spinach compared with control resulted in higher large artery elasticity index (P<0.001), and lower pulse pressure (P<0.001) and systolic blood pressure (P<0.001).
   Nitric Oxide, 2013 · checked 2026-09-29
10. bspn-daily-r4-10 · randomized crossover trial
    With the use of a semirandomized crossover design, 11 men and 7 women [mean ± SEM age: 28 ± 1 y; mean ± SEM body mass index (BMI, in kg/m(2)): 23 ± 1; exercise: 1-10 h/wk] ingested 4 different beverages, each containing 800 mg (∼12.9 mmol) nitrate: sodium nitrate (NaNO3), concentrated beetroot juice, a rocket salad beverage, and a spinach beverage. ... When compared with baseline, systolic blood pressure declined 150 min after ingestion of beetroot juice (from 118 ± 2 to 113 ± 2 mm Hg; P < 0.001) and rocket salad beverage (from 122 ± 3 to 116 ± 2 mm Hg; P = 0.007) and 300 min after ingestion of spinach beverage (from 118 ± 2 to 111 ± 3 mm Hg; P < 0.001)
    J Nutr, 2016 · checked 2026-09-29
11. bspn-daily-r4-11 · prospective cohort
    We analysed 53,854 participants from the Danish Diet, Cancer and Health (DCH) cohort and 197,198 from the UK Biobank. ... Moderate plant-sourced nitrate intake was associated with lower MASLD rates [pooled HRQ3vsQ1 (95%CI): 0.84 (0.76-0.94)] with similar patterns for plant- and vegetable-sourced nitrite. ... moderate plant-sourced intakes (∼1 cup baby spinach/day) were linked to lower MASLD rates
    Clin Nutr, 2026 · checked 2026-09-29
12. bspn-daily-r4-13 · meta-analysis of prevalence
    Synthesizing data from 35 studies published between 2000 and 2021, we demonstrate that wastewater irrigation is a significant source of contamination. ... Certain species show extreme bioaccumulation, with Jew mallow (41.35 mg/kg), beet (23.19 mg/kg), and spinach (pooled mean 2.86 mg/kg) exceeding the EU safety limit (0.2-0.3 mg/kg) by factors of > 130, > 77, and > 9.5, respectively. ... Crucially, the analysis reveals that the use of properly treated or reclaimed wastewater effectively mitigates these risks, with Cd levels comparable to control groups.
    Environ Monit Assess, 2026 · checked 2026-09-29
13. bspn-daily-r4-14 · regulatory decision
    POL-HC-8443 A combination of red spinach, green spinach, red chicory, green chicory, green leaf chard, red leaf chard, red Swiss chard, golden Swiss chard and white Swiss chard Maintain normal blood cholesterol concentrations -/- Non-authorised
    EU Register on nutrition and health claims, claim POL-HC-8443, snapshot 2026-09-21 · checked 2026-09-29
14. bspn-daily-r4-12 · systematic review
    A total of 149 articles describing 78 herbs, food or dietary supplements were reported to interact with warfarin. ... While most food, herbs and supplements can be safely taken in moderation, healthcare professionals should be aware of the increased risk of bleeding when taking several food and herbs. These include Chinese wolfberry, chamomile tea, cannabis, cranberry, chitosan, green tea, Ginkgo biloba, ginger, spinach, St. John's Wort, sushi and smoking tobacco.
    Br J Clin Pharmacol, 2021 · checked 2026-09-29