Sleep quality and duration following evening intake of alpha-lactalbumin: a pilot study

Collagen peptide supplementation before bedtime reduces sleep fragmentation and improves cognitive function in physically active males with sleep complaints

PURPOSE

The primary aim of this study was to examine whether a glycine-rich collagen peptides (CP) supplement could enhance sleep quality in physically active men with self-reported sleep complaints.

METHODS

In a randomized, crossover design, 13 athletic males (age: 24 ± 4 years; training volume; 7 ± 3 h·wk1) with sleep complaints (Athens Insomnia Scale, 9 ± 2) consumed CP (15 g·day1) or a placebo control (CON) 1 h before bedtime for 7 nights. Sleep quality was measured with subjective sleep diaries and actigraphy for 7 nights; polysomnographic sleep and core temperature were recorded on night 7. Cognition, inflammation, and endocrine function were measured on night 7 and the following morning. Subjective sleepiness and fatigue were measured on all 7 nights. The intervention trials were separated by ≥ 7 days and preceded by a 7-night familiarisation trial.

RESULTS

Polysomnography showed less awakenings with CP than CON (21.3 ± 9.7 vs. 29.3 ± 13.8 counts, respectively; P = 0.028). The 7-day average for subjective awakenings were less with CP vs. CON (1.3 ± 1.5 vs. 1.9 ± 0.6 counts, respectively; P = 0.023). The proportion of correct responses on the baseline Stroop cognitive test were higher with CP than CON (1.00 ± 0.00 vs. 0.97 ± 0.05 AU, respectively; P = 0.009) the morning after night 7. There were no trial differences in core temperature, endocrine function, inflammation, subjective sleepiness, fatigue and sleep quality, or other measures of cognitive function or sleep (P > 0.05).

CONCLUSION

CP supplementation did not influence sleep quantity, latency, or efficiency, but reduced awakenings and improved cognitive function in physically active males with sleep complaints.

Alpha-lactalbumin and sleep: A systematic review

Insufficient sleep is a growing global problem, with poor sleep associated with many negative health and performance outcomes. Previous reviews investigating the effect of diet on sleep have highlighted the amino acid tryptophan as a promising sleep-promoting nutrient, with the richest food source of tryptophan, ⍺-lactalbumin, requiring further investigation. Therefore, this systematic review aimed to review the existing evidence of association between ⍺-lactalbumin and sleep. Four electronic databases (CINAHL Complete, Embase, MEDLINE Complete, and SPORTDiscus with Full Text) were searched from database inception to March 2023, with primary research articles included if they contained α-lactalbumin as an independent variable, an outcome measure of sleep or sleepiness, and participants were ≥ 18 years old. Eight studies were reviewed, with four studies recruiting athletic populations (50%) and four recruiting healthy participants (50%). Sleep or sleepiness was measured objectively in six studies (75%), with two studies employing polysomnography and four utilizing actigraphy to assess sleep. Across the studies, 20-60 g of ⍺-lactalbumin was supplemented, with five studies (63%) observing a positive association between α-lactalbumin and sleep. Sleep-onset latency was the primary sleep metric improved following evening supplementation of α-lactalbumin (≤ 3.5 hr pre-sleep), with no studies observing any negative associations with sleep. Data from this review suggest that individuals that have difficulty initiating sleep may benefit most from pre-sleep α-lactalbumin supplementation. Further research is required to establish the effect that α-lactalbumin has on sleep architecture, through the use of more comprehensive sleep analysis tools such as portable electroencephalography or polysomnography, in combination with stringent dietary controls.

Exploring the Role of Dairy Products In Sleep Quality: From Population Studies to Mechanistic Evaluations

Poor sleep quality and insufficient sleep affect a large portion of the population. This is concerning given increasing evidence that poor sleep health is a behavioral risk factor for the development of cardiometabolic diseases. A healthy diet is associated with a plethora of favorable health outcomes, and emerging research now highlights diet as a potential determinant of sleep health that could be leveraged to improve sleep quality. Dairy products are notably rich in tryptophan (Trp), a key substrate for serotonin and melatonin production, which are instrumental for initiating and maintaining sleep. Furthermore, dairy products provide a range of micronutrients that serve as cofactors in the synthesis of melatonin from Trp, which could contribute to sleep-promoting effects. In this review, we evaluate population studies and clinical trials to examine a possible link between dairy consumption and sleep. Available epidemiologic studies illustrate positive associations between dairy intake and sleep outcomes. Moreover, some intervention studies support a causal effect of dairy intake on sleep. Given these data, we discuss potential mechanisms, invite additional clinical research on this topic, and provide insights on how limitations of current studies can be addressed in future trials.

The Impact of Dietary Factors on the Sleep of Athletically Trained Populations: A Systematic Review

Many athletic populations report poor sleep, especially during intensive training and competition periods. Recently, diet has been shown to significantly affect sleep in general populations; however, little is known about the effect diet has on the sleep of athletically trained populations. With sleep critical for optimal recovery and sports performance, this systematic review aimed to evaluate the evidence demonstrating that dietary factors influence the sleep of athletically trained populations. Four electronic databases were searched from inception to May 2022, with primary research articles included if they contained a dietary factor(s), an outcome measure of sleep or sleepiness, and participants could be identified as ‘athletically trained’. Thirty-five studies were included, with 21 studies assessed as positive quality, 13 as neutral, and one as negative. Sleep or sleepiness was measured objectively in 46% of studies (n = 16). The review showed that evening (≥5 p.m.) caffeine intakes >2 mg·kg−1 body mass decreased sleep duration and sleep efficiency, and increased sleep latency and wake after sleep onset. Evening consumption of high glycaemic index carbohydrates and protein high in tryptophan may reduce sleep latency. Although promising, more research is required before the impact of probiotics, cherry juice, and beetroot juice on the sleep of athletes can be resolved. Athletic populations experiencing sleep difficulties should be screened for caffeine use and trial dietary strategies (e.g., evening consumption of high GI carbohydrates) to improve sleep.

Association Between Dietary Protein Intake and Sleep Quality in Middle-Aged and Older Adults in Singapore

Poor sleep has been associated with the increased risk of developing detrimental health conditions. Diet and certain nutrients, such as dietary protein (PRO) may improve sleep. This cross-sectional study aimed to investigate the relationship between PRO intake, their amino acid components, and sources with sleep quality in middle-aged and older adults residing in Singapore. A dataset of 104 healthy subjects between the age of 50 and 75 years old were used. Collected data included 3-day food record and sleep quality [sleep duration, global sleep score (GSS), sleep latency (SL), and sleep efficiency (SE)]. The collected 3-day food records were extracted for PRO, tryptophan (Trp), and large neutral amino acid (LNAA) intake. PRO intake was further categorized into plant and animal PRO. A multivariate multiple linear regression (MLR) was performed to assess the association between PRO intake and sleep quality. Dietary Trp:LNAA ratio was positively associated with sleep duration (β_total: 108.234 h; p: 0.005) after multiple covariates adjustment. Similarly, plant Trp (β_plant: 2.653 h/g; p: 0.020) and plant Trp:LNAA (β_plant: 54.006 h; p: 0.008) was positively associated with sleep duration. No significant associations were observed for both SL and SE. Sleep duration in middle-aged and older Singaporean adults was positively associated with dietary Trp and Trp:LNAA, especially when obtained from plant sources.

Evening Whey Protein Intake, Rich in Tryptophan, and Sleep in Elite Male Australian Rules Football Players on Training and Nontraining Days

OBJECTIVES

To investigate the effect of evening whey protein supplementation, rich in tryptophan, on sleep in elite male Australian Rules Football players.

DESIGN

Double-blinded, counterbalanced, randomized, cross-over study.

METHODS

Sleep was assessed using wrist activity monitors and sleep diaries in 15 elite male Australian Football League players on two training and nontraining days following evening consumption of an isocaloric whey protein supplement or placebo in preseason. A 5-day preintervention period was implemented to determine habitual dietary intake and baseline sleep measures. These habitual data were used to inform the daily dietary intake and timing of ingestion of the evening whey protein supplement or placebo on the intervention days. The whey protein supplement or placebo was consumed 3 hr prior to habitual bedtime.

RESULTS

Separate one-way repeated-measures analyses of covariance revealed no differences between the whey protein supplement and the placebo on sleep duration, sleep onset latency, sleep efficiency, or wake after sleep onset on either training or nontraining days.

CONCLUSIONS

Evening whey protein supplementation, rich in tryptophan, does not improve acute sleep duration or quality in elite male Australian Football League players. However, elite athletes may be able to ingest a high protein/energy intake close to bedtime without impairing sleep, which is important for athlete recovery. Future research should investigate the effect of evening protein intake, high in tryptophan, on sleep duration and quality, including sleep staging during periods of restricted sleep and in poor-sleeping athletes.

ɑ-Lactalbumin Improves Sleep and Recovery after Simulated Evening Competition in Female Athletes

PURPOSE

This study aimed to determine the efficacy of α-lactalbumin (A-LAC) supplementation for improving sleep and performance recovery after simulated evening competition in female athletes.

METHODS

Sixteen trained women (mean ± SD: age, 27 ± 7 yr; mass, 62 ± 10 kg; stature, 167 ± 8 cm) participated in this randomized double-blind three-arm crossover study. Participants completed a simulated evening competition before consuming either an A-LAC whey protein, whey protein placebo (PLA), or water control (CON) beverage. Sleep was monitored via polysomnography, and participants completed a series of physical, cognitive, and perceptual assessments before, and 14 and 24 h after simulated competition.

RESULTS

Non-rapid eye movement stage 2 sleep increased after competition in A-LAC (pre, 199 ± 44 min; post, 212 ± 37 min) but decreased in CON (pre, 228 ± 43 min; post, 195 ± 40 min) and PLA (pre, 224 ± 25 min; post, 211 ± 35 min; P = 0.012). In addition, Yo-Yo Intermittent Recovery Test Level 1 distance improved over time in A-LAC (baseline, 664 ± 332 m; 14 h post, 667 ± 326 m; 24 h post, 781 ± 427 m) compared with CON (baseline, 741 ± 366 m; 14 h post, 648 ± 351 m; 24 h post, 720 ± 407 m) and PLA (baseline, 763 ± 394 m; 14 h post, 636 ± 366 m; 24 h post, 720 ± 396 m; P < 0.001).

CONCLUSIONS

The findings indicate that A-LAC supplementation may be useful for retaining some sleep characteristics after evening competition, leading to improved physical performance in female athletes.

Sleep and Diet: Mounting Evidence of a Cyclical Relationship

Two factors intrinsic to health are diet and sleep. These two behaviors may well influence one another. Indeed, that insufficient sleep adversely impacts dietary intakes is well documented. On the other hand, diet may influence sleep via melatonin and its biosynthesis from tryptophan. Experimental data exist indicating that provision of specific foods rich in tryptophan or melatonin can improve sleep quality. Whole diets rich in fruits, vegetables, legumes, and other sources of dietary tryptophan and melatonin have been shown to predict favorable sleep outcomes. Although clinical trials are needed to confirm a causal impact of dietary patterns on sleep and elucidate underlying mechanisms, available data illustrate a cyclical relation between these lifestyle factors. We recommend adopting a healthful diet to improve sleep, which may further promote sustained favorable dietary practices.

Nutraceuticals as Potential Targets for the Development of a Functional Beverage for Improving Sleep Quality

Functional beverages can be a valuable component of the human diet with the ability to not only provide essential hydration but to deliver important bioactive compounds that can contribute to chronic disease treatment and prevention. One area of the functional beverage market that has seen an increase in demand in recent years are beverages that promote relaxation and sleep. Sleep is an essential biological process, with optimal sleep being defined as one of adequate duration, quality and timing. It is regulated by a number of neurotransmitters which are, in turn, regulated by dietary intake of essential bioactive compounds. This narrative review aimed to evaluate the latest evidence of the sleep promoting properties of a selection of bioactive compounds (such as L-theanine and L-tryptophan) for the development of a functional beverage to improve sleep quality; and the effectiveness of traditional sleep promoting beverages (such as milk and chamomile). Overall, the bioactive compounds identified in this review, play essential roles in the synthesis and regulation of important neurotransmitters involved in the sleep-wake cycle. There is also significant potential for their inclusion in a number of functional beverages as the main ingredient on their own or in combination. Future studies should consider dosage; interactions with the beverage matrix, medications and other nutraceuticals; bioavailability during storage and following ingestion; as well as the sensory profile of the developed beverages, among others, when determining their effectiveness in a functional beverage to improve sleep quality.

Nutritional Interventions to Improve Sleep in Team-Sport Athletes: A Narrative Review

Athletes often experience sleep disturbances and poor sleep as a consequence of extended travel, the timing of training and competition (i.e., early morning or evening), and muscle soreness. Nutrition plays a vital role in sports performance and recovery, and a variety of foods, beverages, and supplements purportedly have the capacity to improve sleep quality and quantity. Here, we review and discuss relevant studies regarding nutrition, foods, supplements, and beverages that may improve sleep quality and quantity. Our narrative review was supported by a semi-systematic approach to article searching, and specific inclusion and exclusion criteria, such that articles reviewed were relevant to athletes and sporting environments. Six databases—PubMed, Scopus, CINAHL, EMBASE, SPORTDiscus, and Google Scholar—were searched for initial studies of interest from inception to November 2020. Given the paucity of sleep nutrition research in the athlete population, we expanded our inclusion criteria to include studies that reported the outcomes of nutritional interventions to improve sleep in otherwise healthy adults. Carbohydrate ingestion to improve sleep parameters is inconclusive, although high glycemic index foods appear to have small benefits. Tart cherry juice can promote sleep quantity, herbal supplements can enhance sleep quality, while kiwifruit and protein interventions have been shown to improve both sleep quality and quantity. Nutritional interventions are an effective way to improve sleep quality and quantity, although further research is needed to determine the appropriate dose, source, and timing in relation to training, travel, and competition requirements.

The impact of tryptophan supplementation on sleep quality: a systematic review, meta-analysis, and meta-regression

CONTEXT

L-tryptophan (Trp) has been documented to aid sleep, but a systematic compilation of its effect on sleep quality is still limited.

OBJECTIVE

We assessed the effect of Trp supplementation on sleep quality via meta-analysis and meta-regression. The effects of daily Trp dose (<1 g and ≥1 g) were also assessed.

DATA SOURCES

A database search was done in PubMed, Medline (Ovid), Cumulative Index to Nursing and Allied Health Literature (CINAHL), and Cochrane and a total of 18 articles were collected.

DATA EXTRACTION

Extracted data from 4 articles were also analyzed using random-effect meta-analysis and meta-regression. Standardized mean difference (SMD) was used in meta-analysis.

DATA ANALYSIS

Results from the study suggested that Trp supplementation can shorten wake after sleep onset (-81.03 min/g, P = 0.017; SMD, -1.08 min [95%CI, -1.89 to -0.28]). In addition, the group receiving ≥1 g Trp supplementation had a shorter wake after sleep onset than the group with Trp < 1g supplementation (Trp <1 g vs Trp ≥1 g: 56.55 vs 28.91 min; P = 0.001). However, Trp supplementation did not affect other sleep components.

CONCLUSION

Trp supplementation, especially at ≥1 g can help improve sleep quality.

Randomized Double-Blind Controlled Trial on the Effect of Proteins with Different Tryptophan/Large Neutral Amino Acid Ratios on Sleep in Adolescents: The PROTMORPHEUS Study

Disturbed sleep is common in adolescents. Ingested nutrients help regulate the internal clock and influence sleep quality. The purpose of this clinical trial is to assess the effect of protein tryptophan (Trp)/large neutral amino acids (LNAAs) ratio on sleep and circadian rhythm. Ingested Trp is involved in the regulation of the sleep/wake cycle and improvement of sleep quality. Since Trp transport through the blood-brain barrier is competing with LNAAs, protein with higher Trp/LNAAs were expected to increase sleep efficiency. This randomized double-blind controlled trial will enroll two samples of male adolescents predisposed to sleep disturbances: elite rugby players (n = 24) and youths with obesity (n = 24). They will take part randomly in three sessions each held over a week. They will undergo a washout period, when dietary intake will be calibrated (three days), followed by an intervention period (three days), when their diet will be supplemented with three proteins with different Trp/LNAAs ratios. Physical, cognitive, dietary intake, appetite, and sleepiness evaluations will be made on the last day of each session. The primary outcome is sleep efficiency measured through in-home electroencephalogram recordings. Secondary outcomes include sleep staging, circadian phase, and sleep-, food intake-, metabolism-, and inflammation-related biochemical markers. A fuller understanding of the effect of protein Trp/LNAAs ratio on sleep could help in developing nutritional strategies addressing sleep disturbances.

Presleep α-Lactalbumin Consumption Does Not Improve Sleep Quality or Time-Trial Performance in Cyclists

We tested the hypothesis that presleep consumption of α-lactalbumin (LA), a fraction of whey with a high abundance of tryptophan, would improve indices of sleep quality and time-trial (TT) performance in cyclists relative to an isonitrogenous collagen peptide (CP) supplement lacking tryptophan. Using randomized, double-blind, crossover designs, cyclists consumed either 40 g of LA or CP 2 hr prior to sleep. In Study 1, six elite male endurance track cyclists (age 23 ± 6 years, V˙O2peak 70.2 ± 4.4 ml·kg-1·min-1) consumed a supplement for three consecutive evenings before each 4-km TT on a velodrome track, whereas in Study 2, six well-trained cyclists (one female; age 24 ± 5 years, V˙O2peak 66.9 ± 8.3 ml·kg-1·min-1) consumed a supplement the evening before each 4-km TT on a stationary cycle ergometer. Indices of sleep quality were assessed with wrist-based actigraphy. There were no differences between the CP and LA supplements in terms of total time in bed, total sleep time, or sleep efficiency in Study 1 (LA: 568 ± 71 min, 503 ± 67 min, 88.3% ± 3.4%; CP: 546 ± 30 min, 479 ± 35 min, 87.8% ± 3.1%; p = .41, p = .32, p = .74, respectively) or Study 2 (LA: 519 ± 90 min, 450 ± 78 min, 87.2% ± 7.6%; CP: 536 ± 62 min, 467 ± 57 min, 87.3% ± 6.4%; p = .43, p = .44, p = .97, respectively). Similarly, time to complete the 4-km TT was unaffected by supplementation in Study 1 (LA: 274.9 ± 7.6 s; CP: 275.5 ± 7.2 s; p = .62) and Study 2 (LA: 344.3 ± 22.3 s; CP: 343.3 ± 23.0 s; p = .50). Thus, relative to CP, consuming LA 2 hr prior to sleep over 1-3 days did not improve actigraphy-based indices of sleep quality or 4-km TT performance in cyclists.

Diet and sleep health: a scoping review of intervention studies in adults

BACKGROUND

Recent research has demonstrated an association between dietary intake and sleep health that can influence chronic disease risk factors. A scoping review of research studies investigating dietary intake and sleep was undertaken to determine the extent and scope of research in laboratory-based, free-living and mixed settings. Additionally, this review determines how well subpopulations and geographical locations are represented and the methodologies used to assess outcome measures.

METHODS

Five online databases were used to identify papers published between 1970 and 2017. Included studies were those conducted in adults and reported both outcomes of interest: (i) sleep health, including sleep restriction and sleep hygiene and (ii) dietary outcomes, including altered nutrients, dietary patterns and supplements.

RESULTS

In total, 129 publications were included with the majority being dietary interventions investigating sleep outcomes (n = 109) with fewer being sleep interventions investigating and reporting dietary outcomes (n = 20). Dietary interventions were most often carried out in free-living environments, in contrast to sleep interventions that were most often carried out in laboratory-based environments. The majority of dietary interventions investigated use of a supplement (n = 66 studies), which was predominantly caffeine (n = 49). Sleep interventions investigated sleep duration only, with the majority (n = 17) investigating the effect of partial sleep restriction under 5.5 h per night on dietary intake, while three studies investigating total sleep deprivation.

CONCLUSIONS

Investigating broader aspects of dietary such as overall diet quality and dietary patterns and other components of sleep health such as quality,  timing and sleep hygiene are important aspects for future research.

Lactalbumin, Not Collagen, Augments Muscle Protein Synthesis with Aerobic Exercise

INTRODUCTION

Protein ingestion and the ensuing hyperaminoacidemia stimulates skeletal muscle protein synthesis in the postexercise period. This response facilitates muscle remodeling, which is important during intensified training. The aim of this study was to determine whether supplementation with α-lactalbumin (LA), with high leucine and tryptophan contents, would improve responses to short periods of intensified aerobic training compared with supplementation with an isonitrogenous quantity of collagen peptides (CP).

METHODS

Endurance-trained participants (5 male, 6 female, 24 ± 4 yr, V˙O2 = 53.2 ± 9.1 mL·kg·min, peak power output = 320 ± 48 W; means ± SD) consumed a controlled diet (1.0 g·kg·d protein) and refrained from habitual training for 11 d while taking part in this double-blind randomized, crossover trial. The two intervention phases, which consisted of brief intensified training (4 × 4-min cycling intervals at 70% of peak power output on 3 consecutive days) combined with the ingestion of LA or CP supplements after exercise (20 g) and before sleep (40 g), were separated by 4 d of washout without protein supplementation (i.e., the control phase). In response to each phase, myofibrillar (MyoPS), sarcoplasmic protein synthesis (SarcPS) rates (via H2O ingestion) and parameters of sleep quality were measured.

RESULTS

LA ingestion increased plasma leucine (P < 0.001) and tryptophan concentrations (P < 0.001) relative to CP. Intensified training increased MyoPS and SarcPS above the washout phase in LA- and CP-supplemented phases (P < 0.01), with increases being 13% ± 5% and 5% ± 7% greater with LA than CP for MyoPS (P < 0.01) and SarcPS, respectively (P < 0.01).

CONCLUSIONS

Despite an isonitrogenous diet, protein synthesis was enhanced to a greater extent when trained participants consumed LA compared with CP during intensified aerobic training, suggesting that protein quality is an important consideration for endurance-trained athletes aiming to augment adaption to exercise training.