This research was conducted via a randomized, placebo-controlled trial with 57 healthy volunteers (comprising of men and women). The participants' absorption of heme and nonheme iron was measured both prior and subsequent to a 12-week course of iron supplementation achieved through the provision of 50mg iron everyday as ferrous sulphate. Alongside, serum and fecal ferritin were observed during the supplementation period and for six months thereafter.

In the initial phase, both heme and nonheme iron absorption had an inverse relation with serum ferritin concentration. With the passage of the 12 week period of iron supplementation, participants, even those with serum ferritin less than 21 microg/L, showed evidence of absorbing less nonheme iron from their diet, but no such change was observed with respect to heme iron from a beef-based meal. Serum ferritin concentration was higher after the supplementation period than after placebo, and this increase remained for more than half a year, barring individuals with low iron stores, in whom the serum ferritin levels returned to their initial numbers within three months. A 2.5-fold increase in fecal ferritin excretion was noted during the supplementation. It becomes evident from these findings that even people with low iron stores adapt by lowering their nonheme iron absorption from food in response to iron supplementation. Despite this adaptation, iron stores appeared to be greater after iron supplementation when compared to placebo, and the difference was sustained across the board, except in the case of people with the lowest iron stores.