Lack of sleep can cause detrimental effects on athletic performance, induce alterations in glucose, carbohydrate and protein metabolism, appetite, food intake, and neuroendocrine function. Other detrimental consequences include changes in cognition, pain perception, immunity, inflammation, metabolism and endocrine function. Today’s high-performance athlete is also subject to frequent travel across several time zones on a regular basis adding further complications to sleep patterns. Hence good sleep hygiene habits cannot always be achieved, challenging clinicians to find natural alternatives to pharmacological interventions which are intrinsically problematic.
Tryptophan (Trp) is a dietary source precursor to the neurotransmitter serotonin and the neuro-secretory hormone melatonin. Evidence exists for beneficial effects of increased Trp intake on cognition, memory, mood and improved sleep. Traverse of dietary Trp through the blood-brain barrier (BBB) is favoured by a higher plasma concentration of Trp in comparison to other competing large neutral amino acids (LNAAs). However, if the diet contains plenty of LNAAs, Trp transport through the BBB is reduced.
Promotion of insulin release from the pancreas, especially by the presence of carbohydrates in the gut lumen, mediates the uptake of LNAAs into muscle but not Trp. Consequently, the Trp/LNAA ratio remains high, and concentrations of other competing LNAAs are reduced, thereby selectively enhancing brain concentrations of Trp. A 2 week pilot study-sleep diaries ascertained sleep patterns in week 1 and the impact of the intervention in week 2 in 19 subjects of a night-time beverage containing protein-source Trp (derived from de-oiled pumpkin seeds) fortified with dextrose to facilitate BBB traverse, demonstrated a significant 9% increase in total sleep time and a 38% reduced sleep disruption. This natural Trp rich source formula merits further investigation to determine its benefits in performance athletes.