Over the past decades, a great amount of research has been done to study the effect of co-ingestion of protein with CHO on post-exercise glycogen resynthesis. Although some early research suggested that adding protein to a CHO drink compared to an isocaloric CHO drink could enhance muscle glycogen recovery after exercise (Berardi, Price, Noreen, & Lemon, 2006; Ivy et al., 2002), there is large consensus nowadays that adding protein to a CHO rich drink does not further enhance muscle glycogen resynthesis post-exercise when ample amounts of CHO (≥ 1.2 g/kg bw/hr) are ingested (Alghannam, Gonzalez, & Betts, 2018; Thomas et al., 2016). There is a substantial amount of evidence indicating that ingestion of (solely) high quality protein stimulates MPS and accelerates recovery post-exercise. Although CHO ingestion immediately post-exercise is suggested for the optimally stimulating glycogen resynthesis, there are some indications that adding CHO to a protein-rich drink has additional benefits besides the restoration of glycogen stores. For example, research performed in rats reported that co-ingestion of CHO and protein increases the anabolic response after training compared to protein ingestion alone (Wang et al., 2017; Wang, Hsieh, Farrar, & Ivy, 2020). Besides, a review by Stark, Lukaszuk, Prawitz, & Salacinski (2012) concluded that adding fast acting CHO to a post-workout protein drink would result in the greatest increase in muscle hypertrophy and lean body mass. This conclusion is primarily based on the observation that adding CHO to a protein drink will result in a greater insulin spike post-exercise, which may amplify the effects of leucine. However, a commentary published a year later (Figueiredo & Cameron-Smith, 2013) concluded that co-ingestion of CHO and protein does not have any additive or synergistic effect on MPS and breakdown regardless of the difference in insulin levels, when an ample amount of protein (20 -25 g) is ingested post-workout. However, the authors do note that more research on this topic is needed to investigate the (long-term) effects of post-workout CHO and protein coingestion versus protein only on muscle hypertrophy and body composition (Figueiredo & Cameron-Smith, 2013). Two years later, a trail by Hulmi et al. (2015) investigated the effects of supplementation of whey protein only versus CHO+whey protein on resistance training adaptations. Both groups performed resistance exercise 2-3 times a week for a period of 12 weeks. After every training session, a drink containing either whey protein only or CHO+whey protein was consumed. After 12 weeks of resistance training and supplementation, no differences in muscular adaptations or muscle strength was observed between the treatment groups. Additionally, some research has been done to investigate the effects of adding CHO to a protein-rich drink on protein uptake and utilisation (Gorissen et al., 2014). The trial by Gorissen et al. (2014) nicely illustrates how the addition of 60 g high glycemic CHO (maltodextrin & dextrose) to 20 g of casein protein, containing intrinsically labelled phenylalanine, affects the uptake of protein and the fate of the ingested protein. The trial included four groups: group one consisted of adolescents receiving a protein only drink and group two consisted of male adolescents receiving a CHO+protein drink. Group 3 and 4 received a similar drink to groups 1 and 2 respectively, however, these groups consisted of older men instead of adolescents. The results clearly showed that the addition of CHO delayed protein digestion and absorption, indicated by the slower appearance of several amino acids from the casein in the circulation. Moreover, MPS was stimulated to a similar degree in the CHO+protein group compared to the protein only group. This was observed in both the young as well as the old males. Thus, addition of 60 g of CHO to 20 g of casein protein slowed the digestion and absorption of the dietary protein without further stimulating MPS.
Why do we have 10 grams of CHO in Nutrition Water?
Nutrition Water currently contains 10 g of CHO in the form of maltodextrin. As stated earlier, the optimal dose for maximal glycogen resynthesis is about 1-1.2 g/kg bw/hr CHO (Ivy et al.,1988; Fritzen et al., 2019). This means that you need lots of CHO directly post-exercise to maximally stimulate glycogen resynthesis. To make a considerable impact on glycogen resynthesis post-exercise, a lot of extra CHO would have to be added to Nutrition Water, which is practically not feasible. Moreover, a vast amount of research shows that a regular diet containing a sufficient amount of CHO and energy is enough to maximally restore glycogen stores after exercise when recovery periods are ≥1 day (Burke et al., 2004).
Research also showed that consumers prefer some CHO in a recovery drink because of e.g. better taste and for quick (psychological) energy after exercise. To comply with the consumer’s demand, we therefore keep at least a small amount of 10 grams CHO in Nutrition Water.
Other results clearly showed that the addition of CHO delayed protein digestion and absorption, indicated by the slower appearance of several amino acids from the casein in the circulation. Moreover, MPS was stimulated to a similar degree in the CHO+protein group compared to the protein only group. This was observed in both the young as well as the old males. Thus, addition of 60 g of CHO to 20 g of casein protein slowed the digestion and absorption of the dietary protein without further stimulating MPS.