Hydration - Protein water

Summer is coming, and you can already feel the sweat dripping of your face. After training your t-shirt is soaking wet (and not from the rain, which is of course extremely likely in Northern Europe). Sound familiar? Well, have no fear! Sweating is one of your bodies mechanisms to keep the body temperature low (1). However, water loss of over 2% of the bodies weight will negatively impact performance, and losing over 6% can even become dangerous (think of exhaustion, unconsciousness, or even a coma)(2). Therefore, it is critical to refill lost water during and after exercise, especially in hot weather when sweat loss is greater. 

You might think that drinking water is sufficient, but only water is not ideal, especially when you need to drink a lot. The composition of a drink has a significant impact on the rate of water absorption and retention, and a few things are important for this: the osmolality of the drink (don’t worry, what this exactly is will be explained further on), the addition of minerals (mainly sodium), and the addition of carbohydrates/sugars (3). These things not only impact the rate at which water is absorbed, but also how well the water will be retained by the body (because there is no point in drinking a lot when you directly pee everything out again).

Effect of osmolality on hydration

Osmolality means, “how many particles/substances there are in a certain fluid or drink”. So, the osmolality defines the concentration (number of particles) of a drink. This is an important factor, since it influences the water absorption in the gut. A way to indicate the osmolality of a drink is to describe it as hypo-, iso- or hypertonic, you may have heard of these terms. Simply said, hypotonic means that the drink is less concentrated (has less particles) compared to our own body fluids. Therefore, such drinks are well absorbed (we like that!). Isotonic drinks have similar concentrations compared to our body fluids and are also well absorbed. In contrast, hypertonic drinks are more concentrated than our own body fluids and consequently are not absorbed well (we like this less, as you may understand). Thus, you can better avoid hypertonic drinks when rapid hydration is desired. It’s better to go for an isotonic drink, and hypotonic drinks seems to be even more effective (3,4)! . 

Vifit Sport Protein Water has an osmolality of 210 – 240 mOsm/kg, which means that it is a hypotonic drink.

Effect of sodium and other minerals on hydration

In addition to losing water through sweat you also lose minerals, particularly sodium, and this needs to be replaced. This is especially important when sweat losses are high and exercise lasts for more than 2h (5). In addition to just replacing losses, adding sodium has several other benefits: sodium improves water absorption in the intestine (6), it stimulates thirst resulting in a drive for you to continue drinking (7), and sodium helps to better retain the ingested fluids (5).     

Effect of carbohydrates on hydration

Adding carbohydrates to a drink is not only important to refill energy stores, it also increases water absorption in the intestine. When these carbohydrates are absorbed in the intestine, this draws water along. However, when concentrations are too high (>8%) this impairs water absorption (3). Thus, it is important to add carbohydrates to a drink to improve water absorption, but not too much because this slows everything down. 

Conclusion

So, what should I take into account for hydrating myself after exercise?

  • Firstly, it is important to avoid the really concentrated hypertonic drinks. You are better off with an isotonic drink. And hypotonic drinks are even better!
  • Secondly, added sodium will replace the loss through sweat, it helps improve water absorption in the intestine, and it helps to retain water in the body.
  • Finally, carbohydrates will also improve water absorption in the intestine, but be careful, avoid too concentrated energy drinks as this slows everything down!

Want to read full articles about this topic? 
1.        Gleeson M. Temperature regulation during exercise. Int J Sports Med. 1998;19(Suppl 2):S96-99.
2.        Sawka MN, Burke LM, Eichner ER, Maughan RJ, Montain SJ, Stachenfeld NS. Exercise and fluid replacement. Med Sci Sports Exerc. 2007;39(2):377–90.
3.        Baker LB, Jeukendrup AE. Optimal composition of fluid-replacement beverages. Compr Physiol. 2014;4(2):575–620.
4.        European Commission. Composition and specification of food intended to meet the expenditure of intense muscular effort , especially for sportsmen. 2001; Available from: https://ec.europa.eu/food/sites/food/files/safety/docs/sci-com_scf_out64_en.pdf
5.        Shirreffs SM, Sawka MN. Fluid and electrolyte needs for training, competition, and recovery. J Sports Sci. 2011;29(SUPPL. 1):37–41.
6.        Coyle EF. Fluid and fuel intake during exercise. J Sports Sci. 2004;22(1):39–55.
7.        Stachenfeld NS. Sodium ingestion, thirst and drinking during endurance exercise. Sport Sci Exch. 2014;27(122):1–5.