The effect of chronic soluble keratin supplementation in physically active individuals on body composition, blood parameters and cycling performance

• Published in: Journal of the International Society of Sports Nutrition Vol. 15; no. 1; p. 47
• Main Authors: Crum, Emma M, McLeay, Yanita D, Barnes, Matthew J, Stannard, Stephen R
• Format: Journal Article
• Language: English
• Published: United States BioMed Central Ltd 27.09.2018; Taylor & Francis Ltd; BioMed Central; Taylor & Francis Group
• Subjects: Adult; Amino acids; Athletes; Athletic Performance - physiology; Bicycling; Body Composition; Casein; Caseins - administration & dosage; Chemical bonds; Comparative analysis; Cross-Over Studies; Cycling; dexa; Diet; Dietary protein; Dietary Supplements; Endurance; ergogenic aid; Ergogenic aids; Exercise; Fatigue; Fitness training programs; Food and nutrition; Humans; Intervention; Keratin; Keratins - administration & dosage; Male; Musculoskeletal system; Oxygen Consumption; Performance-Enhancing Substances - administration & dosage; Physiological aspects; Poultry; Proteins; Single-Blind Method; skeletal muscle; Studies; Young Adult; New Zealand; Dietary protein; Exercise; Ergogenic aid; Performance; DEXA; Skeletal muscle
• ISSN: 1550-2783; 1550-2783
• DOI: 10.1186/s12970-018-0251-x

Keratins are structural, thiol-rich proteins, which comprise 90% of total poultry feather weight. Their favourable amino acid profile suggests the potential for use as a protein source and ergogenic aid for endurance athletes, following treatment to increase digestibility. This study investigated whether 4 weeks of soluble keratin (KER) consumption (0.8 g/kg bodyweight/day) by 15 endurance-trained males would have favourable effects on body composition, blood and cardiorespiratory variables, and cycling performance, compared to casein protein (CAS). Supplementation was randomized, blinded and balanced, with a minimum eight-week washout period between trials. An exercise test to measure oxygen consumption during submaximal and maximal cycling exercise was completed at the start at and end of each intervention. Anthropometric (DEXA) and blood measures were made prior to and following each intervention period. Total body mass and percentage body fat did not change significantly (p > 0.05). However, a significantly greater increase in bone-free lean mass (LM) occurred with KER compared to CAS (0.88 kg vs 0.07 kg; p < 0.05). While no change in LM was evident for the trunk and arms, leg LM increased (0.45 ± 0.54 kg; p = 0.006) from baseline with KER. KER was not associated with changes in blood parameters, oxygen consumption, or exercise performance (p > 0.05). These data suggest that KER is not useful as an ergogenic aid for endurance athletes but may be a suitable protein supplement for maximizing increases in lean body mass.