The Effect of an Eight-Week High n-3 and Low n-6 PUFA Dietary Intervention, on Submaximal and Peak Oxygen Consumption in Trained Cyclists

L. J. Hale1, G. Davison1, L. Passfield1,2, B. Gyimah3, M. R. Lindley4

1School of Sport and Exercise Sciences, University of Kent, UK

2Faculty of Kinesiology, University of Calgary, Canada

3Centre for Analytical Science, Department of Chemistry, Loughborough University, UK

4School of Sport, Exercise and Health Sciences, Loughborough University, UK

This study investigated the effect of an eight-week dietary intervention designed to increase n-3 PUFA consumption and reduce dietary intake of n-6 PUFA on VO2peak and oxygen consumption (VO2) during submaximal exercise. Fourteen trained male cyclists were randomly assigned to two independent groups. The experimental group received n-3 PUFA supplementation (2600mg EPA and 1800mg DHA per day) and followed a dietary intervention designed to reduce n-6 PUFA intake. The placebo group received organic soy oil and a placebo dietary intervention that maintained their habitual daily n-6 PUFA intake. Venous blood samples were obtained pre supplementation, at week four and at week eight of the dietary intervention to determine erythrocyte incorporation of n-3 and n-6 PUFA. Pre and post the dietary intervention, participants completed 4 x 7 minutes of submaximal cycling on a Lode ergometer at four discontinuous incremental power outputs (100 W, 125 W, 150 W,175 W). Steady state oxygen consumption VO2 was assessed during each cycling bout. Following a 15-minute rest, participants performed an incremental ramp test to exhaustion (intensity increasing by 30 W·min−1) for the determination of VO2peak. In the fish oil supplemented group, erythrocyte incorporation of total n-3 PUFA increased (from 10.4±2.5 to 20.1±2.8 %) and total n-6 PUFA decreased (from 40.3±1.9 to 30.8±1.3 %) over the eight-week supplementation period. There were no differences in VO2peak (pre 61.7±9.0, post 61.0±7.7 ml/ kg/ min). During steady state submaximal cycling, there were no differences in oxygen consumption (VO2) at any of the four power outputs in the fish oil supplemented group (e.g. 125 W pre 2.32±0.26, post 1.98±0.11 L/min). In conclusion, despite the dietary intervention successfully increasing erythrocyte n-3 PUFA and reducing n-6 PUFA incorporation over an 8-week intervention period, this had no effect on oxygen consumption during submaximal exercise or VO2peak performance.