The present study examined the possibility that a high bran and phytate intake over a long period would induce changes in the intestines or its microflora leading to a reduction of the inhibitory effect of dietary phytates on iron absorption. Such changes might occur in vegetarians and populations in developing countries with a usually very high dietary intake of phytates. The inhibitory effect of bran on Fe absorption was compared between a group of strict vegetarians with a regular high phytate intake and a control group by use of wheat rolls with and without bran labeled with 55Fe and 59Fe. The average individual decrease of the Fe absorption from adding the bran was 92 and 93% in the two groups, respectively. No intestinal adaptation to a high phytate intake could be observed. This finding has wide nutritional implications.