Abstract
BackgroundKeratins 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).MethodsSupplementation 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.ResultsTotal 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).ConclusionsThese 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.
Highlights
Keratins are structural, thiol-rich proteins, which comprise 90% of total poultry feather weight
We have previously shown that ingestion of up to 40 g per day of soluble KER is safe and palatable when supplementing a balanced diet in humans [8]
Participants were blinded to the contents of the supplements and only one participant was able to confidently guess which condition they were on
Summary
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. Poultry feathers contain ~ 90% of their total weight as keratin, which gives the material its characteristic light but rigid structure [2]. In New Zealand, chickens are widely bred for use in commercial meat production (~ 82,000,000 birds annually) [3], but their feathers, which represent ~ 10% of total chicken weight, are indigestible to humans and other monogastrics
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