Low carbohydrate ketogenic diets (LCKD) where carbohydrate intake is <50 g/d have become popular is many populations, including endurance athletes( Reference Volek, Noakes and Phinney 1 ). The complete effect of this diet on nutrient absorption and its potential to influence health has not been fully uncovered( Reference Paoli, Rubini and Volek 2 ). A 14 day ketogenic diet in females demonstrated no effect on RBC, Hb or Hct levels in healthy females( Reference Nazarewicz, Ziolkowski and Vaccaro 3 ), but longer duration research in an athletic population is lacking. The aim of the current research is to examine the effect of a LCKD versus a high carbohydrate diet, on blood count indicators of iron status in endurance athletes.
Following ethical approval 19 participants selected into a high carbohydrate (HC) (65 % kcal CHO, 20 % kcal fat, 14 % kcal protein) or LCKD (>75 % kcal fat, 10–15 % kcal protein and <50 g/d CHO) group for 12 weeks. Participants also completed an endurance training protocol during the trial. Whole blood samples were analysed using the haematology analyser before and after selection into each dietary group. RM ANOVA was used to assess changes in indicators of iron status in participants over time. Paired t-tests assessed changed within group over time.
RBC – red blood cell; Hb – haemoglobin; Hct – haematocrit; MCV – mean corpuscular volume; MCH – mean corpuscular haemoglobin; MCHC – mean corpuscular haemoglobin concentration; red cell distribution width.
* Significant difference at P < 0·05; a Significant difference within group over time at P < 0·05.
RBC, Hb, and Hct significantly decreased over time. Within group Hct decreased between weeks 1 and 12 in the HC participants and Hb, MCH and MCHC decreased within the LCKD participants.
Endurance training has been associated with increased plasma volume with exercise induced inflammation also implicated as a possible cause for iron deficiency in athletes( Reference Hinton 4 ). It is possible the endurance training added during this trial had a similar effect on iron status within these participants. However it does not explain the difference in Hb, MCH and MCHC between HC and LCKD participants. Due to the effect iron status has on oxygen transport to muscle, further research is warranted to investigate the effect of a ketogenic diet on iron status in endurance athletes.