Diets
plant antinutrients decreases mineral and nutrient bioavailability
In plain terms: Do plant foods contain antinutrients that limit nutrient absorption?
Strong support Diets 🔬 Includes disconfirming
RefutedContestedStrong support
consensus score 0.93
Yes — phytate, oxalate, tannins and lectins measurably reduce mineral absorption, though processing (soaking, fermentation, cooking) largely mitigates this and many have offsetting benefits.
📅 Last reviewed: 2026-07-14 ⓘ
Evidence ladder
How far up the ladder this claim has climbed. A high consensus on a low rung means "consistent so far," not "proven in people."
Top evidence so far: Human trials (RCT / n-of-1)
MechanismIn-vitroAnimalObservationalRCTMeta-analysis
How the studies fall
6 support 1 contradict 0 tested null 0 mixed · 7 sources, 6 independent groups
What the evidence shows
Phytate, oxalate and tannins measurably reduce mineral absorption, demonstrated with stable-isotope iron studies in humans: dephytinising fortified sorghum and comparing bean lines both change fractional iron absorption directly. Processing matters as much as the compounds — soaking, fermentation and cooking cut phytate, and fermentation raises phytase activity.
The evidence (18)
| Source | Grade | Stance | Quality | Finding |
|---|---|---|---|---|
| Cercamondi CI, Egli IM, Zeder C, Hurrell RF 2014 · Br J Nutr | RCT | supports | high | Three human iron-absorption studies in 50 young women fed dephytinised Fe-fortified sorghum meals; absorption measured by stable-isotope incorporation into erythrocytes. Study 1: 8.5% at 17 mg polyphenols vs 3.2% at 73 mg and 2.7% at 167 mg (P<0.001); 73 vs 167 mg did not differ (P=0.9). Study 2, at 167 mg: NaFeEDTA 4.6% vs FeSO4 2.7% (P<0.001), still below 10.7% from 17 mg-polyphenol FeSO4 meals. Study 3: laccase cut polyphenols 167 to 42 mg without improving absorption (4.8 vs 4.6%, P=0.4), while ascorbic acid raised it to 13.6% (P<0.001). The 50 women span all three studies. |
| Lindenmayer LA, Mayer MJ, Schmöckel SM, Frank J 2026 · Journal of Agricultural and Food Chemistry | in-vitro | contradicts | moderate | Six saponin-rich (bitter) and six low-saponin (nonbitter) quinoa genotypes went through a standardized simulated digestion, nine runs each. Soluble mineral fractions were low and alike in both: iron 1.0% vs 1.1%, zinc 2.0% vs 2.0%, calcium 0.6% vs 0.4%. Carotenoid and vitamin E bioaccessibility and micelle charge (-26.4 vs -26.9 mV) also did not differ, and the few endpoints that did favoured the bitter seeds. Saponins were not measured here; the authors say fibre, phytate and polyphenol differences, not saponins, likely explain it. This is bioaccessibility, not absorption in people. |
| Udomkun P, Tirawattanawanich C, Ilukor J, Sridonpai P, Njukwe E, Nimbona P, Vanlauwe B 2019 · Food Chemistry | mechanism | mixed | moderate | Cassava, rice, and banana flours replaced wheat in cereal-legume composite flours; the study assayed composition and calculated phytate- and oxalate-to-mineral molar ratios against published critical values, and did not measure absorption in anyone. Ratios to calcium and zinc all fell below those critical values, except phytate to iron, which exceeded its threshold. Once calcium and phytate were considered together, every blend but full rice replacement was predicted to give inadequate zinc bioavailability. |
| Arsov A, Tsigoriyna L, Batovska D, Armenova N, Mu W, Zhang W, Petrov K, Petrova P 2024 · Foods | observational | supports | moderate | A narrative review of antinutrients in plant foods and the bacteria that degrade them; it reports no new experiments. It states that phytates chelate zinc, iron, calcium, magnesium, manganese and copper, and that 4-9 mg of phytic acid per 100 g of food can cut human iron absorption five-fold. Fermentation results it collects from other groups are mixed: soluble oxalates fell almost 94% and phytate in tarhana 89%, but flavonoids and hydrolysable tannins rose 52% and 99%. In one cited human study, 11 women taking condensed tannins for 3 weeks showed no change in iron bioavailability. |
| Hariharamohan M, Chindarkar M, Swain HS, Rajesh N, Rajesh V 2026 · RSC Advances | in-vitro | supports | moderate | Kerala red rice broth fermented 18 h (3 batches) developed phytase activity of 0.12 U/mL, up from negligible. Synthetic phytate-calcium, -iron and -zinc complexes soaked in that broth released far more mineral than in unfermented broth: calcium +1190%, iron +566%, zinc +93%. The two arms were sampled at different endpoints (360 min fermented vs 240 min unfermented); at the matched 15-minute point calcium (19,689 vs 1,661 ppb) and iron (7,113 vs 1,294 ppb) were already far apart, while zinc was not (448 vs 421 ppb). No human absorption was measured. |
| Elliott H, Woods P, Green BD, Nugent AP 2022 · Nutr Bull | observational | supports | moderate | A narrative review of sprouting in cereals and legumes. It states that phytate, the primary storage form of phosphorus in plants, forms insoluble complexes with minerals such as iron and zinc and thereby prevents their absorption in the body, and that sprouting activates phytase, which degrades phytate and improves mineral bioaccessibility. The review summarises other researchers' studies rather than reporting new data and gives no effect sizes; the authors add that so few studies exist that the effect on nutrient bioavailability cannot be predicted accurately. |
| Herter-Aeberli I, Fischer MM, Egli IM, Zeder C, Zimmermann MB, Hurrell RF 2020 · J Nutr | RCT | supports | high | Stable-isotope iron-absorption trial in healthy young women aged 21-29 fed iron-fortified tef injera. In study A (22 women), absorption from the 100% tef meal was 1.5% (IQR 0.7-2.8%); replacing 10% of the tef with whole wheat flour during fermentation cut phytic acid from 0.62 to 0.20 g per meal and raised absorption to 5.3% (2.4-7.1%), and added Aspergillus niger phytase cut phytic acid to 0.02 g and raised it to 3.6% (1.6-6.2%); both P<0.05. In study B (18 women), replacing 50% or 75% of the iron salt with NaFeEDTA did not change absorption (3.3%, P>0.05). |
| White PJ, Broadley MR 2009 · New Phytol. 2009;182(1):49-84 | observational | supports | moderate | 2009 New Phytologist review of biofortifying crops with iron, zinc, copper, calcium, magnesium, selenium and iodine: 'This article reviews aspects of soil science, plant physiology and genetics underpinning crop biofortification strategies'. It reports crops developed with 'reduced concentrations of antinutrients, such as oxalate, polyphenolics or phytate, which interfere with their absorption', and with raised promoter substances (ascorbate, beta-carotene, cysteine-rich polypeptides) that 'stimulate the absorption of essential mineral elements by the gut'. It measures no absorption itself. |
| Abebe Z, Haileyesus A 2026 · Food Science & Nutrition | mechanism | supports | low | Ethiopian food-lab study of cauliflower leaf powder baked into wheat bread. Fermenting the leaves for 8 days cut oxalate from 2.74 to 0.78 mg/100 g and phytate from 1.15 to 0.51 mg/100 g, more than boiling or blanching (three replicates from one batch). Bread with 9% leaf powder had 36% more protein and 157% more fibre than wheat-only bread, and its calculated phytate-to-iron and phytate-to-zinc ratios fell from 0.046 and 0.076 to 0.015 and 0.028. Iron and zinc absorption was never measured; the 15%-20% bioavailability gain is a figure the authors took from other researchers. |
| Ogunc, Yenicag, Rakicioglu 2026 · Nutr Bull | observational | supports | moderate | Turkey's two national nutrition surveys, 7,017 participants in 2010 and 9,832 in 2017, with phytate intake estimated by matching dietary recalls to a global phytate food-composition database. Median intake rose from 535.3 mg/day to 658.0 mg/day (p < 0.001), bread and cereals contributing most. Judged by phytate-to-mineral molar ratios, most participants fell in the low iron-bioavailability and moderate zinc-bioavailability bands. Absorption itself was not measured; the bioavailability labels come from published threshold ratios. |
| Harahap IA, Suliburska J, Weber D, Esatbeyoglu T 2026 · Ultrason Sonochem | in-vitro | supports | low | Soybeans were made into tempeh, with or without ultrasound treatment, fermented 48 h at 30 C or 36 C, then run through a simulated stomach-and-intestine digestion. Fermenting raised calcium versus plain soybeans, with no difference between the two temperatures, while magnesium and iron were unchanged. Tempeh given ultrasound at both soaking and cooking and fermented at 36 C released the most calcium and iron during digestion, roughly 40-50% more calcium than the other tempeh treatments. The study did not measure phytate or any other antinutrient. Three replicates per condition. |
| Sateikaite I, Samaei Y, Khan M, Carvalho I, Lazarte CE 2026 · J Health Popul Nutr | observational | supports | moderate | In 47 rural Mozambican children aged 2-5, three days of photo-assisted diet recall found cereal-dominated diets: zinc intake met 48-80% of the recommended amount and calcium only 9-12%. Phytate-to-mineral ratios computed from food-composition tables ran 8.5-59 for zinc, 3.2-25.8 for iron and 0.11-2.19 for calcium; 89% of the children's diets were above the zinc threshold of 15, and 11% were below it. The study measured what the children ate, not what they absorbed - no blood or absorption measurements were taken, and the authors say serum iron and zinc would be needed for that. |
| Petry N, Egli I, Campion B, Nielsen E, Hurrell R 2013 · J Nutr | RCT | supports | high | Paired double-meal crossover stable-isotope study in 20 young women comparing 4 common-bean lines. Fractional iron absorption from a low-phytate (lpa) bean high in polyphenols was 6.1% (95% CI: 2.6, 14.7) — 60% higher than its own normal-phytate parent and 130% higher than the unmatched low-polyphenol parent (both P < 0.001); the lpa line low in polyphenols gave 4% (95% CI: 1.8, 8.7), 50% higher than its own parent. 'There was no difference between the lpa beans high or low in PPs.' Absorption was per test meal; the paper does not report iron-status outcomes. |
| Karabulut G, Günal-Köroğlu D, Yılmaz H, Erskine E, Capanoglu E 2026 · Ageing Research Reviews | observational | supports | moderate | A narrative review of antinutrients in plant foods, reporting no experiments of its own. It states that phytates, oxalates, lectins, tannins, saponins and enzyme inhibitors 'can impair nutrient absorption and reduce the bioavailability of proteins, carbohydrates, and essential minerals', but gives no figures for how much absorption falls. It also argues the other side: that the same compounds may counteract oxidative stress, inflammation and mitochondrial decline, and that fermentation, soaking and germination cut the harmful effects while preserving the bioactive ones. |
| Cook JD, Reddy MB, Burri J, Juillerat MA, Hurrell RF 1997 · Am J Clin Nutr | observational | supports | moderate | In 57 volunteers, each given four radioiron absorption tests across six studies, iron absorption from 50 g cooked cereal (rice, wheat, maize, oats, millet, sweet and bitter quinoa) was strongly and inversely correlated with the cereals' phytate content. Absorption was under 1% from every iron-fortified cereal; removing the added iron raised it by an average 37%, and adding 50 mg ascorbic acid raised it by 270%. The authors concluded that grain type itself makes little difference, but that milling and processing that lower phytic acid should improve iron availability significantly. |
| Olar-Pop L, Cornea-Cipcigan M, Ciont CC, Suharoschi R, Pop RM, Pop OL 2026 · Comprehensive Reviews in Food Science and Food Safety | animal | supports | low | A meta-analysis of 27 controlled animal experiments (chickens, mice, rats) asking whether probiotics offset antinutrient-rich diets. Every group ate the antinutrient-rich diet; only the probiotic varied, so no antinutrient-free comparison was run. In broilers probiotics raised liver iron (SMD 2.05, 95% CI 0.91-3.20) and liver ferritin (SMD 2.85, 0.90-4.80) but not haemoglobin; in rats they cut kidney calcium-oxalate deposits (SMD 0.77, p=0.0001) but not urinary oxalate. Certainty was low, heterogeneity 96-98%, and the iron result lost significance after correcting for publication bias. |
| Hackl LS, Moretti D, Sabatier M 2025 · Adv Nutr | observational | supports | moderate | A narrative review by Nestlé researchers pulling together 22 human isotope studies of iron absorption from soy. Phytate was strongly limiting: adding 300 mg phytic acid to a soy-isolate drink cut absorption from 21.7% to 2.15%, stripping phytate out raised absorption up to 4.8-fold, and putting it back returned absorption to where it started. Vitamin C more than tripled absorption. Adjusted absorption from soy meals ranged 4.1% to 22.2%. The authors did not run a systematic literature search and did not pool the studies statistically. |
| Sandberg AS, Brune M, Carlsson NG, Hallberg L, Skoglund E, Rossander-Hulthén L 1999 · Am J Clin Nutr | RCT | supports | high | Five single-meal human iron-absorption experiments, 8-11 subjects each, using extrinsic 55Fe/59Fe labelling with whole-body retention and erythrocyte uptake. With 10 mg P added to white-wheat rolls as IP5, IP4 or IP3: 'In experiment 1, iron absorption was reduced by 39%, whereas there was no significant effect on iron absorption in experiments 2 and 3.' With IP3+IP4 mixtures from fermented phytate, absorption 'was reduced by 54% and 64%, respectively.' The stated objective was IP3, IP4 and IP5; the paper does not report an isolated test of IP6. |
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