Author(s): MASCARENHAS, L., HAMILTON, D.L., ROBERTS, S., PUMPA, K.L., MILES, K., BARNARD, J., CALLAHAN, D., MRUTHUNJAYA, A.K.V., TORRIERO, A., CONDO, D. , Institution: DEAKIN UNIVERSITY, Country: AUSTRALIA, Abstract-ID: 940

INTRODUCTION:
Insufficient sleep can negatively impact training, performance, and increase injury risk in active populations. Consequently, strategies to improve sleep in active populations have been gaining popularity. Tryptophan (TRP), an amino acid and precursor for serotonin and melatonin metabolism has been established for its sleep augmenting benefits. However, pure TRP is regulated as a prescription medicine in Australia. Alpha-lactalbumin (ALAC), is a whey protein with high TRP (4.8 mg/g) content and has been assessed for its effects on mood, alertness, and sleep outcomes. However, there is a lack of consensus on the dose and timing of consuming ALAC for optimising TRP availability. The present study aims to define the dose of ALAC required to saturate the plasma TRP and TRP:LNAA ratio, over a 210 min time course.
METHODS:
Sixteen healthy active adults, aged 18-35 years, completed this double-blinded randomised crossover trial. Participants visited the Deakin lab on four different occasions with a gap of 2.5 hours from their last meal. Each visit involved consuming a single evening dose of ALAC (10 g, 20 g, 30 g, and 40 g) in a random latin square order. In a crossover manner, each participant received all doses, separated by a washout period. Venous blood samples were collected at five time points up to 210 min post-consumption. Visual Analogue Scales were provided to assess sensory preferences and gastrointestinal (GI) symptoms associated with the four ALAC doses. The plasma TRP:LNAA ratio time-course was analysed using mixed models adjusting for sex, body weight, and baseline.
RESULTS:
Across all doses the apparent peak for TRP and TRP:LNAA ratio occurred at 120-180 min post consumption and were significantly different from baseline for 30 g and 40 g doses of ALAC (p<0.02). Pairwise comparisons of plasma TRP levels at 120 and 180 min confirmed that 30 and 40 g produced significantly higher TRP concentrations than 10 g (p<0.01) or 20 g (p<0.02). A similar trend was observed with 30 g ALAC on the plasma TRP:LNAA ratio at the apparent peak of 180 min (p<0.02). However, no significant differences were reported in TRP concentrations and TRP:LNAA ratio between higher doses of 30 g and 40 g (p=0.30). This indicates that 30 g of ALAC may be a saturating dose for both TRP and TRP:LNAA ratio. Additionally, AUC analysis for the time course at each dose reported similar trends, reinforcing evidence of a saturation effect on TRP concentrations and TRP:LNAA at 30 g of ALAC . There were no significant differences in the sensory attributes and GI symptoms reported across the time course for all doses, indicating that dosing up to 40 g is equivalent for digestive comfort to dosing at 10 g of ALAC.
CONCLUSION:
Our findings indicate that 30 g ALAC has a saturating effect on the plasma TRP concentrations and the TRP:LNAA ratio, producing an apparent peak at 180 min post-consumption. These data may support the optimisation of ALAC timing and dosing for associated sleep, mood and cognitive enhancement.