Timing is everything, but does it really matter? Impact of 8-weeks morning versus evening iron supplementation in ballet and contemporary dancers

Abstract

The effectiveness of a morning versus evening oral iron supplement strategy to increase iron stores was explored. Ballet and contemporary dancers with serum ferritin (sFer) < 50μg/L (n = 14), were supplemented daily with 105 mg elemental oral iron in either the morning (Fe_AM) or evening (Fe_PM) for 8 weeks. A control group (n = 6) with sFer >50μg/L were given no supplement over the same period. Dancers’ sFer were measured at baseline and post-intervention. Assessment of daily training load, dietary intake, and menstruation were made. A significant interaction (p < 0.001) showed the within group sFer change over the 8-week intervention in Fe_AM (+25.9 ± 10.5μg/L) and Fe_PM, (+22.3 ± 13.6μg/L) was significantly different to CON (−30.17 ± 28.7μg/L; both p = 0.001). This change was not different between Fe_AM and Fe_PM (p = 0.778). sFer levels within Fe_AM and Fe_PM significantly increased over the 8-weeks; however, they significantly decreased in the CON group (all p < 0.05). Post-intervention sFer levels were no longer different between the three groups (p > 0.05). Training load, dietary intake, and number of menstrual cycles incurred were similar between Fe_AM and Fe_PM (p > 0.05). Oral iron supplementation in either the morning or evening appears equally effective in increasing sFer levels in dancers with sub-optimal iron status.