Vitamin C and iron absorption from meals
What it found
Vitamin C boosts the amount of iron the body takes up from plant foods, and can cancel out the blocking effect of tea.
The effect is smaller when meat, fish or poultry are in the meal.
What they found
Studies in people
Plant iron boosted
Adding ascorbic acid to vegetable meals raised nonheme iron absorption, and the rise was directly proportional to how much ascorbic acid was present. In one study, orange juice with 40 to 50 mg ascorbic acid raised absorption from a labelled egg meal from 3.7% to 10.4%.
Tea blocking reversed
Tea strongly blocks nonheme iron absorption from cereal meals, and ascorbic acid reverses that block. With enough ascorbic acid present, absorption can exceed that from the plain meal with neither tea nor ascorbic acid.
Meat and fish
Meat and fish also boost nonheme iron absorption, but their effect and that of ascorbic acid are not additive. In one comparison, 100 mg ascorbic acid raised absorption 3.19-fold from a meat-free semisynthetic meal but only 1.67-fold from a meal containing beef.
Contaminant iron
Iron from rust (ferric oxide) and soil or water (ferric hydroxide) added to maize porridge was poorly absorbed, at 0.01% and 1.5%. Adding 100 mg ascorbic acid raised these to 0.5% and 6.7%, still low for the meal and the iron-deficient people studied.
Timing and cooking
Ascorbic acid works only if present in the meal: 500 mg taken with a meal raised absorption about sixfold, but the same dose taken four to eight hours earlier had little effect. After boiling, about 70% of 50 and 100 mg supplements remained in the reduced form and still boosted absorption, but in baked foods such as soy biscuits and wheat bread very little remained reduced and no boost occurred.
Animal and lab studies
How it works
Ascorbic acid forms a complex with ferric iron at acid pH that stays soluble at the alkaline pH of the duodenum. In rats given ferric chloride, absorption was 17% when ascorbic acid was added before alkalisation and 5.3% when added after.
What the authors conclude
“High cost and instability during food storage are the major obstacles to using ascorbic acid in programs designed to combat nutritional iron deficiency anemia.”
Also in their conclusions
- They say ascorbic acid is a powerful enhancer of nonheme iron absorption and can reverse the inhibiting effect of substances such as tea and calcium/phosphate.
- They note that its influence may be less pronounced in meals of high iron availability, such as those containing meat, fish or poultry.
- They report that high cost and instability during food storage are the major obstacles to using ascorbic acid in programs designed to combat nutritional iron deficiency anemia.
How it was done
Iron deficiency is common, and most dietary iron comes from plant sources that the body absorbs poorly. The authors wanted to understand how vitamin C changes that absorption, and whether it could be used to improve iron nutrition.
The authors pulled together absorption studies in people who ate test meals labelled with radioactive iron tracers. Meals were based on maize, wheat, soya or rice, eaten with and without added ascorbic acid, and in some cases with tea, calcium/phosphate, meat or fish. Some lab work and rat experiments looked at how ascorbic acid keeps iron soluble.
What it can’t tell you
- The absorption studies measured iron uptake from single test meals, so they cannot show what long-term iron stores or iron deficiency rates would do.
- The authors note that the long-term effects of very large daily doses of ascorbic acid on iron balance in people are not known.
The paper
- Title
- Interaction of vitamin C and iron
- Type
- Study
- Evidence
- Studies in people · animals · lab
- Summarised from
- Full text
- Cite
- Lynch SR, Cook JD (1980). Interaction of vitamin C and iron. Annals of the New York Academy of Sciences. doi:10.1111/j.1749-6632.1980.tb21325.xFree full textPubMed 6940487DOI
Summary written 26 Sep 2026. Check it against the paper before it changes what you eat. How we summarise papers · Report an error