Estimation of iron requirements for women by numerical analysis of population-based data from the National Health and Nutrition Surveys of Japan 2003–2007

Iron requirements were estimated from the results of the National Health and Nutrition Surveys of Japan 2003–2007 using the numerical analysis of requirements based on an integral equation. The numerical analysis used population-based data on iron nutriture, the prevalence of inadequate iron status, and the distribution of iron intakes. The cutoff value for inadequate iron status was defined as a serum ferritin concentration <30 ng/mL. Iron intakes and menstrual blood losses followed a log-normal distribution and published values were corrected accordingly to calculate usual values. For women aged 18–29 years old, the median of the estimated median iron requirement (corresponding to the estimated average requirement by using the terminology of the dietary reference intakes) was 7.59 mg (range, 6.86–8.11). The median of the estimated usual iron intake covering the needs of women with 80 mL per cycle of menstrual blood loss was 11.27 mg (range, 10.16–12.00), and the median of the usual iron intake covering the needs of 97.7% of women was 13.93 mg (range, 12.55–14.81). For women aged 30–49 years old, the corresponding figures were 8.13 mg (range, 7.96–8.69), 11.95 mg (range, 11.72–12.77), and 14.71 mg (range, 14.44–15.72).