Glycerol is now an accepted supplement, after its removal from the World Anti-Doping Agency’s (WADA) banned list in 2018. While it was once prohibited due to concerns over its potential to mask banned substances, research has demonstrated that its masking effects are minimal. This opens up opportunities for athletes to use glycerol to support hydration in endurance sports and hot humid environments.
So What is Glycerol?
Glycerol is a naturally occurring molecule in the body, involved in the structure of cell membranes and the storage of fatty acids. It’s a clear, sweet-tasting liquid that, when mixed with water, enhances the body’s ability to absorb and retain fluids. This property makes glycerol particularly useful for athletes seeking to manage hydration during intense physical activity or in hot conditions.
How does Glycerol Help Hydration?
Glycerol’s key benefit lies in its ability to promote hyperhydration. Usually the body likes to keep it’s body water pretty constant. So hydrating beyond a certain point isn’t possible without risking health such as hyponatraemia (low electrolytes) and performance. However, glycerol stimulates water absorption and by increasing the concentration of water in the body, it helps retain an additional 600mL of fluid compared to drinking water alone. This effect can be especially beneficial in sports where maintaining hydration is crucial for performance, particularly in hot environments or during endurance events.
The position statement from Sports Dietitians Australia (SDA) highlights the importance of pre-exercise hydration strategies, especially when athletes face exertional heat stress. Preloading with glycerol or sodium before exercise can expand plasma volume and improve heat tolerance during events in hot conditions.
What the science says and how to use it?
Though glycerol research paused during its ban, emerging studies continue to offer mixed results. Some show significant improvements in endurance, particularly in heat tolerance and fluid retention, while others are less conclusive. However, glycerol may offer performance benefits for endurance athletes and those needing rapid rehydration, such as after weigh-ins for weight-category sports or between intense training sessions.
Glycerol may also be useful in occupational settings, particularly those that involve significant heat stress, such as firefighting or military operations.
So what does this mean? Hyperhydrating for endurance events in particular, where hydration is challenged or heat regulation hindered, MAY be of benefit by helping you cope in the heat, delay dehydration and actually improve overall performance.
What are the Risks / Side Effects?
As with any supplement, you need to go in knowing the risks. As you consume glycerol with a large amount of water, the expansion of fluid within the body can cause nausea, gastrointestinal distress and headaches. Although rare, it does highlight the need to test the supplement in training first and ensure you spread the intake out over a longer time period to minimise any risk and make sure it suits you.
Also, as you are hydrating and holding more fluid, you will be going into the race heavier – so you need to weigh up the benefits vs. detriment for you individually.
Glycerol, a natural compound, can be easily found in pharmacies as clinical-grade products. While the risk of contamination is low, it’s still something athletes who undergo testing should consider. Currently, there are no glycerol products that are batch tested for purity on the market.
Proposed Intake Protocol
These ranges are based on our comprehensive review of the literature and should be trialled in consultation with a Sports Dietitian to find the dosage that suits you and your performance needs.
Based on current research, athletes should consult with a sports dietitian to individualize their glycerol intake. The common recommendation is to consume 1-1.2g of glycerol per kg of body weight mixed with 25-30mL of water per kg of body weight before exercise.
FOR EXAMPLE: if you were 70kg, you would mix 70-85g of glycerol into 1750-2100mL of water.
Some research also suggests that glycerol loading with salt and carbohydrate included can add to it’s benefits; so you could replace the water with a carbohydrate containing sports drink or consume the glycerol-water drink with your usual pre-race fuelling meal/snack.
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References:
- McCubbin, A. J., Allanson, B. A., Caldwell Odgers, J. N., Cort, M. M., Costa, R. J., Cox, G. R., Crawshay, S. T., Desbrow, B., Freney, E. G., Gaskell, S. K., Hughes, D., Irwin, C., Jay, O., Lalor, B. J., Ross, M. L., Shaw, G., Périard, J. D., & Burke, L. M. (2020). Sports Dietitians Australia Position Statement: Nutrition for Exercise in Hot Environments. International Journal of Sport Nutrition and Exercise Metabolism, 30(1), 83-98. Retrieved Oct 10, 2024, from https://doi.org/10.1123/ijsnem.2019-0300
- Nelson JL, Robergs RA. Exploring the potential ergogenic effects of glycerol hyperhydration. Sports Med 2007;37:981-1000.
- Van Rosendal SP, Coombes JS. Glycerol use in hyperhydration and rehydration: Scientific update. Med Sport Sci 2012;59:104-12.
- Coutts A, Reaburn P, Mummery K, Holmes M. The effect of glycerol hyperhydration on Olympic distance triathlon performance in high ambient temperatures. Int J Sport Nutr Exerc Metab 2002;12:105-19
- Anderson MJ, Cotter JD, Garnham AP, Casley DJ, Febbraio MA. Effect of glycerol-induced hyperhydration on thermoregulation and metabolism during exercise in the heat. Int J Sport Nutr Exerc Metab 2001;11:315-33.
- Goulet EB, De La Flore A, Savoie FA, Gosselin J. Salt + Glycerol-Induced Hyperhydration Enhances Fluid Retention More than Salt- or Glycerol-Induced Hyperhydration. Int J Sport Nutr Exerc Metab 2017; https://doi.org/10.1123/ijsnem.2017-0310
- Goulet ED. Review of the effects of glycerol-containing hyperhydration solutions on gastric emptying and intestinal absorption in humans and in rats. Int J Sports Nutr Exerc Metab 2009;19:547-60.
