Iron status of active premenopausal women

Abstract

Decreased iron status has been reported in groups of endurance athletes, but the effects of exercise programs of moderate intensity are still under investigation. The purpose of this study was to examine the iron status of a group of 32 active premenopausal women, aged 21 to 40 years, and to compare it to that found in a NHANES III data set representing 261 age-matched women. We also sought to evaluate the relationships of iron status with average weekly exercise time, dietary intake, and other factors affecting iron status. Iron status was assessed using plasma ferritin measurements; dietary intake was evaluated using a semi-quantitative food frequency questionnaire; average weekly exercise was assessed by self-report. Subjects engaged in an average of 358.3 ± 172.3 minutes of exercise per week, consisting mostly of aerobic dance, with a mean participation time of 8.1 (0.2 – 31.0) years. Mean plasma ferritin concentration for the study group was significantly lower than that of the NHANES III sample (32.5 vs 51.7 μg/L, p<0.0). However, the percentage of women exhibiting suboptimal ferritin levels was not different between the two groups, with 31.1% () of the study group and 28.4% () of the NHANES III sample falling below 20 μg/L. Using correlation analyses, several factors were found to be significantly associated with iron status. Average minutes of weekly exercise was negatively correlated with plasma ferritin level (r=−0.36, p<0.05). About 50% of the women took supplements containing either iron or vitamin C, and a positive correlation was found between plasma ferritin concentration and both supplemental iron (r=0.59), p<0.05) and supplemental vitamin C intake (r=0.45, p<0.05). No association was found between ferritin level and dietary intakes of protein, iron, vitamin C, fiber, or servings per week of redmeat or fish and poultry. Active premenopausal women had lower ferritin levels but no increased prevalence of impaired iron status, as compared to normal population controls. Exercise intensity was inversely related to iron status, while supplemental iron and vitamin C intakes were positively related to iron status. Based on current recommendations of moderate exercise for health promotion, the association found between average weekly exercise time and iron status is of interest. In light of the hypothesized relationship between elevated iron stores and risk of chronic disease, exercise may represent a method of reducing iron stores without increasing the prevalence of impaired iron status. The relationship between exercise and iron status deserves further investigation in groups at risk for elevated iron stores, such as men and postmenopausal women.