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Iron

Adults following vegetarian or vegan diets have lower iron stores (serum ferritin) than meat-eaters, because plant foods supply only non-haem iron, which is less well absorbed; mean haemoglobin is similar across diet patterns, while the evidence on anaemia prevalence is mixed. Eating ascorbate-rich fruit with meals probably raises ferritin and haemoglobin modestly. Adding vitamin C to oral iron supplements adds little, and iron supplements raise iron status in menstruating women at the cost of more gastrointestinal side effects.

  • Energy
  • Vegan

Evidence retrieved up to

What the research shows

In trials in women and children, including ascorbate-rich fruits or fruit juices with meals probably raised serum ferritin and haemoglobin modestly, though it showed little effect on measured iron absorption.

Moderate certaintyFurther research may change the size of the effect.
No known concerns at usual amountsBenefit

Who this is about

women aged 15 to 74 and children

Practical note

Graded moderate, in line with the review authors' GRADE assessment: a 2026 meta-analysis of 15 randomised trials (1381 participants) found serum ferritin about 9 micrograms per litre and haemoglobin about 1.3 g/L higher with ascorbate-rich fruit added to meals; the effect on iron absorption itself was low certainty and not significant.

Vegan note

Vitamin C-rich fruit and vegetables eaten with meals are a food-based way to improve non-haem iron absorption on a plant-based diet.

Sources

Despite lower iron stores, mean haemoglobin is similar in adults following vegetarian or vegan diets and in meat-eaters; whether anaemia is more common on plant-based diets is unclear, as the studies that assessed it point in different directions.

Very low certaintyThis is uncertain; treat it as a lead, not a finding.
No known concerns at usual amountsUnclear

Who this is about

adults following vegetarian or vegan diets

Practical note

Graded very low: descriptive comparisons of observational studies without pooling, inconsistent findings on anaemia prevalence, and a review whose authors work for a food company. One systematic review found mean haemoglobin of 136-140 g/L across diet groups but higher anaemia prevalence in the few studies that measured it; an older literature review reported more iron deficiency anaemia among vegetarians.

Vegan note

Applies to vegetarians and vegans; premenopausal women are the group most often reported with low iron status.

Safety note

Low iron stores and anaemia are identified with blood tests by a health professional; symptoms alone do not show them.

Sources

Adults following vegetarian or vegan diets have lower serum ferritin, a marker of iron stores, than adults who eat meat, and depleted iron stores are common among them, especially among women.

Low certaintyFurther research is likely to change this.
No known concerns at usual amountsRisk

Who this is about

adults following vegetarian or vegan diets

Practical note

Graded low: the evidence is observational (a 2018 meta-analysis pooling 24 cross-sectional studies found ferritin about 30 micrograms per litre lower in vegetarians, with a larger gap in men than in women). The direction is consistent across reviews, but cross-sectional designs start at low certainty and nothing here justifies upgrading.

Vegan note

Plant foods supply only non-haem iron, which is absorbed less well than haem iron from meat; a systematic review cites an Institute of Medicine estimate that iron requirements are 1.8 times higher for vegetarians and vegans.

Sources

In trials of menstruating women, daily iron supplements raised haemoglobin and iron stores, improved exercise performance and lowered self-reported fatigue, while increasing gastrointestinal side effects such as constipation and loose stools.

Moderate certaintyFurther research may change the size of the effect.
Take care: see the safety noteBenefit

Who this is about

menstruating women

Practical note

Graded moderate: a 2016 Cochrane review of 67 trials (8506 women) rated the haemoglobin outcome high quality and the anaemia and iron deficiency outcomes moderate quality, but only 10 trials were at low risk of bias. A 2015 meta-analysis of 43 trials found roughly doubled odds of gastrointestinal side effects with ferrous sulfate versus placebo, with no clear relation to dose.

Safety note

Iron supplements cause gastrointestinal side effects in a meaningful share of adults and belong with a clinician who has confirmed low iron status.

Sources

In adults with iron deficiency anaemia taking oral iron, adding vitamin C supplements produced at most a small, likely clinically insignificant extra rise in haemoglobin compared with oral iron alone.

Moderate certaintyFurther research may change the size of the effect.
Take care: see the safety noteNo clear effect

Who this is about

adults with iron deficiency anaemia taking oral iron

Practical note

Graded moderate: a 2024 meta-analysis of 10 randomised trials found a pooled haemoglobin difference of 0.14 g/dL, and a 440-person randomised equivalence trial found iron alone equivalent to iron plus vitamin C; downgraded one level for risk of bias (the trial was open-label). That trial gave 100 mg iron with or without 200 mg vitamin C every 8 hours for 3 months.

Safety note

Iron supplements are best used with a clinician, who can confirm low iron with blood tests and look for its cause.

Sources