Saturday, December 27, 2014

Glycerol, An Overlooked Ergogenic Supplement? 10-12g of Glycerol May Increase Lean Mass Without Training. Plus: Effects on Adrenals & AST + Lactate Response to Exercise

Interestingly, the study at hand suggests that glycerol may make you more musclar, even if you don't life. Crazy, but true (photo by awesomebody).
As a SuppVersity reader the potential ergogenic effect of the backbone of triglycerides are no news to you. The number of studies investigating the effects of glycerol on exercise performance and/or the adaptive response to exercise is yet low. Against that background, even a rodent study like the one by Eric Francelino Andrade from the Federal University of Lavras is worth its own SuppVersity article, I guess.

In said study, the Brazilian researchers evaluated the training adaptation and physical performance parameters in rats orally supplemented with glycerol,glucose, or saline, and submitted to moderate aerobic exercise.
Glycerol can be used in conjunction with creatine to hyperhydrate (Easton. 2007).

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Thirty male rats were trained for 6 weeks and administered the supplements during the last 4 weeks of the experiment. Animals were distributed in a completely randomized factorial 2 × 3 design (with or without exercise and 3 substrates) and received 864 mg/kg body of either glucose or glycerol in solution.

For human beings this equals human equivalents of 140mg/kg or ~10-12g of both, glucose and glycerol, for an adult. If this amount of glycerol had the same effects on humans at it did on the rodents in the study at hand, this would mean that it would lead to non-significant increases in lean body mass, even if the men and women who take it, were not working out.
Figure 1: Overview of the study design (top) and changes in protein content (~lean mass) and fat content of the carcass of trained and untrained rodents in the glycerol, glucose and saline groups at the end of the study period (Andrade. 2014)
The data from the rodent study at hand does yet also suggest that glycerol may at the same time non-significantly inhibit the lean mass gains that occur in response to aerobic training.

Glycerol as an adrenal supplement?

In contrast to the previously cited changes in lean body mass, which are not the result of a simple increase in body water (that's the beauty of actually cutting your "hairy subjects" open - you don't have to use BIA or DEXA scans to measure their lean mass), the effects on the weight of the adrenals of the animals was statistically significant in both, the trained and the non-trained rodents.
Figure 2: Organ weights (top row) and lactate (middle row) and aspartate aminotransferase (AST | lower row) levels at the end of the study period and after workouts, respectively (Andrade. 2014)
In the exercise trained rodents, there was also a significant reduction in the protein oxidation marker AST in both, the glucose and glycerol group. An obvious sign that both, pure glucose and the polyol (sugar alcohol) compound were used as alternative fuel during the exhaustive workouts, with the latter providing greater reductions in lactate build-up than the former.
What do previous studies say? Previous studies suggests that both glycerol, as well as combined creatine and glycerol can be used to hyperhydrate before exercise and thus to reduce the thermal and cardiovascular strain (Easton. 2007). This practice can also increase the exercise performance of endurance athletes like cyclists (Montner. 1996). Consumed in large amounts of 80g and in conjunction with 2L water, glycerol has also been shown to decreases body weight in athletes & increase overall performance in sedentary subjects, as previously reported at in a previous article of mine.
What do we make of these results? The increased lean mass in the non-trained rats is good news for every couch potato. The non-significance of the difference in trained rats is good news for athletes. The same goes for the reduced AST and lactate levels which suggest that glycerol is effectively used as alternative fuel and thus a candidate for pre- and intra-workout supplements for low-carbers.

Both the increases in heart and adrenal weight are physiological responses to exercise. In that, it is good news that the heart weight did not increase more in the glycerol group, despite the increased adrenal weight in these rats (otherwise, this may be interpreted as a result of pathological stress). The possible mechanisms for the increased adrenal weight are thus not of sympathetic (stressful) nature. Rather than that, the increased adrenal weight "may be related to an increase in body fluid volume caused by glycerol, decreasing relative sodium concentration (hyponatremia) (Von Duvillard. 2004), and increasing mineralocorticoid (aldosterone) secretion and adrenal gland mass (Decaux. 2003)" (Andrade. 2014). Overall, the results of the study still confirm that the ergogenic effects of glycerol are beyond the well-known hyperhydration properties caused by this substance | Comment on Facebook!
  • Andrade, Eric Francelino, et al. "Adaptation to physical training in rats orally supplemented with glycerol." Canadian journal of physiology and pharmacology 93.999 (2014): 1-7.
  • Decaux, Guy, et al. "Low plasma bicarbonate level in hyponatremia related to adrenocorticotropin deficiency." The Journal of Clinical Endocrinology & Metabolism 88.11 (2003): 5255-5257.
  • Easton, Chris, Stephen Turner, and Yannis P. Pitsiladis. "Creatine and glycerol hyperhydration in trained subjects prior to exercise in the heat." International journal of sport nutrition and exercise metabolism 17.1 (2007): 70-91.
  • Montner, P., et al. "Pre-exercise glycerol hydration improves cycling endurance time." International Journal of Sports Medicine 17.01 (1996): 27-33. 
  • Von Duvillard, Serge P., et al. "Fluids and hydration in prolonged endurance performance." Nutrition 20.7 (2004): 651-656.