Low-phytate wholegrain bread instead of high-phytate wholegrain bread in a total diet context did not improve iron status of healthy Swedish females: a 12-week, randomized, parallel-design intervention study

PurposeTo investigate the effects of eating wholegrain rye bread with high or low amounts of phytate on iron status in women under free-living conditions.MethodsIn this 12-week, randomized, parallel-design intervention study, 102 females were allocated into two groups, a high-phytate-bread group or a low-phytate-bread group. These two groups were administered: 200g of blanched wholegrain rye bread/day, or 200g dephytinized wholegrain rye bread/day. The bread was administered in addition to their habitual daily diet. Iron status biomarkers and plasma alkylresorcinols were analyzed at baseline and post-intervention.ResultsFifty-five females completed the study. In the high-phytate-bread group (n=31) there was no change in any of the iron status biomarkers after 12weeks of intervention (p>0.05). In the low-phytate bread group (n=24) there were significant decreases in both ferritin (mean=12%; from 327 to 27 +/- 6 mu g/L, geometric mean +/- SEM, p<0.018) and total body iron (mean=12%; from 6.9 +/- 1.4 to 5.4 +/- 1.1mg/kg, p<0.035). Plasma alkylresorcinols indicated that most subjects complied with the intervention.ConclusionsIn Swedish females of reproductive age, 12weeks of high-phytate wholegrain bread consumption had no effect on iron status. However, consumption of low-phytate wholegrain bread for 12weeks resulted in a reduction of markers of iron status. Although single-meal studies clearly show an increase in iron bioavailability from dephytinization of cereals, medium-term consumption of reduced phytate bread under free-living conditions suggests that this strategy does not work to improve iron status in healthy women of reproductive age.