Relationships between faecal phytate and mineral excretion depend on dietary phytate and age.

摘要

The adverse effect of phytate on mineral absorption, and the effect of dietary phytate and age on the relationship between faecal phytate and faecal mineral excretion, were examined. 14 young women (aged 19-24 yr) and 14 elderly women (64-75 yr) were studied for 2 metabolic periods (MP). In MP1, the subjects consumed a controlled high-phytate (HP) diet for 10 days; in MP2, they were on a low-phytate (LP) diet for 10 days. In each period, diet samples and complete faecal samples for 5 days were collected to analyse phytate and mineral contents. Mineral concn. in diet and faeces were measured by inductively coupled plasma atomic emission spectrometry. Linear regression analysis was used to examine the associations between faecal phytate and mineral excretion. The degradation rate of dietary phytate was about 77% for young women, which was significantly lower than that of elderly women (86%) (P < 0.05). Faecal phytate excretion was positively correlated with mineral excretion (Ca, P, Fe and Zn) in both the HP and LP diet groups in young women (P < 0.05). The linear relationship tended to be greater during the LP diet period compared with the HP diet period in young women. However, no association was found between phytate excretion and mineral excretion in elderly women. In summary, undegraded dietary phytate (10-20%) had a negative effect on mineral absorption in young women, and the relationship between faecal phytate and mineral excretion was affected by both dietary phytate and age.