Is chocolate milk the best recovery drink?

..from Recovery from Strenuous Exercise (Routledge, 2022)

The use of (chocolate) milk-based drinks to deliver a palatable form of fluid, carbohydrate, protein and sodium has been investigated in great detail (Karp et al, 2006; Cockburn et al, 2010; Saunders, 2011; Spaccarotella & Andzel, 2011; Pritchett & Pritchett, 2012; Desbrow et al, 2014; Seery & Jakeman, 2016; Amiri et al, 2018; Alcantara et al, 2019; Loureiro et al, 2021; Russo et al, 2021). Compared to traditional sports drinks, adding protein may help to increase performance, mitigate muscle damage, promote euglycemia and facilitate glycogen resynthesis (Kerksick et al, 2018). The consumption of carbohydrate and protein during the early phases of post-exercise recovery has been shown to positively affect subsequent exercise performance and could be of specific benefit for athletes involved in multiple training or competition sessions on the same or successive days (Beelanet al, 2010). In fact, an investigation by Desbrow et al, (2014) demonstrated that the consumption of a milk-based liquid meal supplement following exercise resulted in improved fluid retention when compared with cow’s milk, soy milk and a carbohydrate-electrolyte drink. Additionally, cow’s milk and soy milk were similarly effective at enhancing fluid restoration in comparison with the carbohydrate-electrolyte drink. Furthermore, Seery & Jakeman (2016) noted (n=7) a significant advantage in the restoration of body net fluid balance over a five-hour period following exercise and thermal dehydration to -2% of body mass by a metered replacement of milk compared with a carbohydrate-electrolyte drink or water. Consumed as the sole recovery diet, neither milk nor the carbohydrate-electrolyte drink provided optimal nutrition for recovery. However, the authors concluded that the protein component of milk which is essentially absent from carbohydrate-electrolyte drinks and water may further enhance glycogen resynthesis and promote muscle protein synthesis. In addition, the minerals (calcium, phosphorus, zinc and iodine) and vitamins (A, E and B group vitamins) in milk that are not present in carbohydrate-electrolyte drinks contribute to the athlete’s micro-nutrient requirements. Furthermore, Cockburn et al (2010) examined the effects of acute milk-based carbohydrate - protein supplementation timing on the attenuation of exercise-induced muscle damage (EIMD). Four independent matched groups of eight healthy males consumed milk-based carbohydrate-protein supplements before (PRE), immediately after (POST) or 24 hours after muscle-damaging exercise. Active delayed-onset muscle soreness (DOMS), isokinetic muscle performance, reactive strength index (RSI) and creatine kinase (CK) were assessed immediately before and 24, 48 and 72 hours after EIMD. POST and at 24 hours demonstrated a benefit in limiting changes in active DOMS, peak torque and RSI over 48 hours, compared with PRE. PRE showed a possible benefit in reducing increases in CK over 48 hours and limiting changes in other variables over 72 hours. The authors suggested that consuming milk-based carbohydrate-protein supplements after muscle-damaging exercise is more beneficial in attenuating decreases in muscle performance and increases in active DOMS at 48 hours than ingestion prior to exercise. In the above study, the authors highlighted an important point: consuming 500 ml rather than 1,000 ml following exercise may be easier for athletes to implement, as fewer calories will be consumed, and it may lead to less stomach fullness and discomfort. Since flavoured milk, such as chocolate milk, has a similar carbohy- drate and protein content to that of many carbohydrate-replacement drinks, it may be an effective means of refuelling glycogen-depleted muscles, enabling individuals to exercise at a high intensity during a second workout of the day (Karp et al, 2006). Therefore, flavoured milk may be considered an effective alternative to commercial fluid replacement and carbohydrate-replacement drinks for recovery from exhausting, glycogen-depleting exercise. This agrees with the work of Amiri et al,(2018), who noted that chocolate milk seems to be a good candidate to aid in recovery, since it contains carbohydrate, protein, water and electrolytes. The authors’ systematic review and meta-analysis revealed that chocolate milk consumption after exercise improved time to exhaustion compared to placebo or carbohydrate + protein + fat drinks. Additionally, chocolate milk consumption led to lower blood lactate compared to a placebo. Therefore, chocolate milk provides either similar or superior results on recovery indices compared to other recovery drinks, and thus represents an alternative and often economic replacement. Also in agreement, Pritchett and Pritchett (2012) added that low-fat chocolate milk consists of a 4:1 carbohydrate-protein ratio (similar to many commercial recovery beverages), and provides fluids and sodium to aid in post-workout recovery. Consuming chocolate milk (1.0–1.5•g•kg^–1 h^–1) immediately after exercise and again at two hours post-exercise appears to be optimal for exercise recovery and may attenuate indices of muscle damage. Furthermore, Lunn et al (2012) summarised, relative to a carbohydrate-only beverage, consumption of (fat-free chocolate) milk after an endurance exercise bout significantly increased skeletal muscle protein synthesis, attenuated whole-body proteolysis, enhanced phosphorylation of eukaryotic translation factor 4E- binding protein 1, and suppressed or maintained molecular activity of protein breakdown during recovery. In addition, milk consumption was as effective as the control at maintaining muscle glycogen during the recovery period; and performance in a subsequent exercise bout was enhanced compared with the control. Also finding positive outcomes were Spaccarotella and Andzel, (2011). The results from their study suggested that consuming low-fat chocolate milk between morning and afternoon practices may be as good as an isovolumetric amount of carbohydrate-electrolyte beverage at promoting recovery, measured by shuttle run time to fatigue, among Division III football players. However, mixed findings were noted by Rankin et al,(2018). They found that the consumption of 500 ml of milk post repeated sprinting and jumping had a positive effect on the attenuation of losses in muscle function, thus improving recovery, compared to an energy-matched carbohydrate drink in female athletes. However, although a benefit of milk was seen for rate of force development and a five-metre sprint (small) over the first 24 hours of recovery, the outcomes for RSI, ten or 20-metre sprint performance, muscle soreness and tiredness, CK and CRP were unclear. Further positive outcomes were noted by Russo et al (2021). The authors found that small, frequent doses of a flavoured cow’s milk beverage are well tolerated and support greater overall recovery opti-misation during the acute recovery period (ie, two hours post-exercise) compared to a non-nitrogenous carbohydrate-electrolyte beverage.

In a less favourable study on the benefits of chocolate milk for recovery, Alcantara et al (2019) conducted a systematic review (11 studies) of the impact of cow’s milk intake on exercise performance and recovery of muscle function and concluded that, based on the current evidence, it cannot be determined whether cow’s milk has a positive effect on exercise performance and recovery of muscle function in humans. However contrary to this, a literature review by Saunders (2011) found that there is a variety of evidence indicating that carbohydrate + protein ingestion and chocolate milk in particular, may promote post-exercise recovery and enhance subsequent exercise performance when compared with carbohydrate alone. The author suggested that these effects could be the result of positive influences on glycogen resynthesis, protein turnover, muscle disruption, rehydration or a combination of these factors; although it seems that carbohydrate + protein beverages (including chocolate milk) may have the potential to improve recovery under some exercise conditions. Thus, although greater clarity is required before specific recommendations can be provided, the current evidence suggests that chocolate milk is a good choice as a recovery beverage for endurance athletes.