Recently, my mom went to donate blood and was told her iron levels were too low. She has since been advised to eat foods rich in Vitamin C.
So the question arises… why does Vitamin C aid in iron absorption? As the Biochemist in the family, I told her I would look into it!
Here is what I have gathered:
We digest two kinds of iron: heme and nonheme iron. Heme iron, which comes from hemoglobin and myoglobin, is easily absorbed. On the other hand, the absorption of nonheme iron, the more common kind of heme, depends on meal composition. Ascorbic acid is one form of Vitamin C and enhances nonheme iron absorption. It is also known to reverse the inhibiting effect of tea and calcium/phosphate on iron absorption. For meals with high iron availability-such as meat, fish, or poultry, its effect may be less needed. However for meals with mostly vegetables (and my mom has recently become vegetarian,) the amount of ascorbic acid available directly enhances the amount of iron absorption. How does Ascorbic acid do this? It promotes iron absorption by forming a chelate (a compound containing a ligand bonded to a central metal atom such as iron) with ferric iron at acidic pH. Where this ligand bond between the acid and iron occurs…I am not sure. From looking at the ascorbic acid molecular structure, it would be reasonable to suggest it occurs at one of its many hydroxyl groups. (since its an acid, it is not without hydroxyls!!) There are a few caveats. This form of Vitamin C comes at a high cost and is unstable during food storage. These two features detract from Vitamin C’s ability to promote iron absorption for those dealing with low iron levels.
For more information- see http://www.ncbi.nlm.nih.gov/pubmed/6940487