Reply to RP Glahn

5. Cook JD, Layrisse M, Martinez-Torres C, Walker R, Monsen E, Finch CA. Food iron absorption measured by an extrinsic tag. J Clin Invest 1972;51:805–15. 6. Layrisse M, Martinez-Torres C, Cook JD, Walker R, Finch CA. Iron fortification of food: Its measurement by the extrinsic tag method. Blood 1973;41:333–52. 7. Björn-Rasmussen E, Hallberg L, Walker RB. Food iron absorption in man. Isotopic exchange of iron between labeled foods and between a food and an iron salt. Am J Clin Nutr 1973;26:1311–9.