Pairing up vitamin C and iron supplements could mean trouble for your stomach and intestines.
Although vitamin C aids iron absorption, taking the two supplements together could increase the risk of ulcers or aggravate inflammatory conditions such as Crohn's disease or ulcerative colitis. Only take iron supplements if advised to by your healthcare provider and ask how to minimize interactions with foods and other supplements.
Most people do not need to take an iron supplement. In fact, taking too much iron can increase oxidative stress in your body and may do more harm than good. Iron is found in abundance in meats, fish, and poultry. Non-animal sources include soybeans, tofu, quinoa, and lentils and other beans. Additionally, some foods, such as breakfast cereals, are fortified with iron. If you are anemic or take iron on the advice of your healthcare provider, follow your healthcare provider's instructions closely regarding supplements.
Co-supplementation of ferrous salts (iron) with vitamin C exacerbates oxidative stress in the gastrointestinal tract leading to ulceration in healthy individuals, exacerbation of chronic gastrointestinal inflammatory diseases and can lead to cancer. Reactive oxygen and nitrogen species (RONS) have been ascribed an important role in oxidative stress. Redox-active metal ions such as Fe(II) and Cu(I) further activate RONS and thus perpetuate their damaging effects. Ascorbic acid can exert a pro-oxidant effect by its interaction with metal ions via a number of established RONS generating systems which are reviewed here. Further studies are required to examine the detrimental effects of nutraceuticals especially in chronic inflammatory conditions which co-present with anaemia.
Iron and ascorbic acid form a potentially toxic cocktail. Ascorbic acid has been shown to exhibit both anti-oxidant and pro-oxidant effects in a dose related fashion. The chemical mechanisms given above have been established demonstrating the potential for these compounds to interact and oxidatively damage surrounding tissues. Even in healthy subjects a positive or negative deviation from the optimal plasma ascorbic acid level results in oxidative damage. The detrimental effects of large quantities of ascorbic acid and iron in healthy subjects and patients with GI inflammatory diseases warrant further investigation. In addition dietary supplements containing iron and ascorbic acid may be deleterious as these components do not naturally come in concentrated form (as in supplementation tablets).
This suggests that a multivitamin should not contain iron. If someone needs supplemental iron, it should be administered separately, and taken a few hours apart from Vitamin C, or a multivitamin containing Vitamin C.
The evidence for inflammation resulting from the interaction of ferrous ions and ascorbate in animals already exists. These studies can be extended to humans by exploiting some of the many studies undertaken on vitamin and mineral supplementation. A recent study conducted by the Food Standards Agency (UK) is the largest to date and could be exploited in a follow up to assess the long term effects of iron and ascorbic acid co-supplementation. As iron uptake in the GI tract is regulated by plasma iron levels, analysis of plasma iron should dictate the requirement for iron and vitamin C supplementation to avoid residual iron damaging the GI tract.
Iron supplements: the quick fix with long-term consequences. Fisher, A. E., Naughton, D. P., Nutrition Journal 2004 Jan 16;3:2. http://nutritionj.com/content/3/1/2