Written by Daniel Roytas, MHSc (Nutrition), BHSc (Naturopathy), Dip. RM, MANTA
Taking vitamin C with iron is commonly recommended by clinicians to enhance the bioavailability and metabolism of iron. Vitamin C has been shown to stimulate a number of physiological mechanisms involved in the intestinal absorption, cellular uptake and metabolism of iron including;
Despite these beneficial interactions, it has been reported that there may be unfavourable interactions between iron and vitamin C. In a study of 40 healthy volunteers supplemented with 14 mg/d of ferrous sulphate and either 60 mg/d or 260 mg/d of ascorbic acid for 12 weeks, a transient rise in white blood cell oxidative DNA damage was observed after 6 weeks of supplementation. By 12 weeks, the levels of oxidative DNA damage had resolved, which is thought to be due to an adaptive response within the cell to increase repair enzymes or by enhancing iron sequestration into ferritin6. Could it be that the observed increase in cellular repair enzyme activity and ferritin concentrations in patients taking iron and vitamin C, is actually a sign of the body going in to “damage control”?
It is also well known that supra-physiological doses of vitamin C or iron taken alone, generates reactive oxygen and nitrogen species, lipid peroxidation and oxidative stress7. When taken together, is it possible that these two nutrients could create a potent oxidative cocktail? Animal studies seem to confirm this hypothesis. For example, in one study when rats were injected with a solution of iron and vitamin C in to their gastro-intestinal tracts, they developed gastric ulcers. Interestingly, the rats did not develop ulceration when vitamin C or iron were injected separately8.
Vitamin C is known to reduce ferric iron (Fe3+) in to ferrous state (Fe2+), which is required for incorporation in to haeme2. In other words, without the presence of vitamin C, sufficient iron may not be made available for erythropoiesis. But do these nutrients really need to be given at the same time? It has been proposed that when given together in a bolus, this reducing effect can induce the Fenton reaction, resulting in the activation of peroxides, hydrogen peroxide (H202) and hydroxyl radical generation. When ingested together, iron and vitamin C may generate substantial concentrations of pro-oxidants, which are purported to cause tissue damage in the gastro-intestinal tract, leading to the formation of gastric ulcers7.
The combination therapy of vitamin C and iron is something that many clinicians prescribe patient’s with iron deficiency in clinical practice, without a second thought. Given the potential harms associated with this practice, is it time for us to re-evaluate the co-prescription of iron and vitamin C?