Donating blood

[roopy]

Vitamin C and iron (ascorbic acid is the generic name for vitamin C)

The key role of ascorbic acid for the absorption of dietary nonheme iron is generally accepted. The reasons for its action are twofold: (1) the prevention of the formation of insoluble and unabsorbable iron compounds and (2) the reduction of ferric to ferrous iron, which seems to be a requirement for the uptake of iron into the mucosal cells.

http://www.ncbi.nlm.nih.gov/pubmed/2507689