As far the topics for today's installment of the SuppVersity Science Round Up are concerned, you are actually only a couple of lines away from reading about one that's on the list: The effects of glycerol on exercise performance. I don't have to tell you though that this is not everything. Other things I believe you may be interested in are...
- childhood obesity, physical education and attention at school
- wheat gluten hydrolysate and how they don't come up to the expectations early trials have raised
- ammonia accumulation brain-fog, toxicity, liver 'pathologies' and workout performance
- running next to a street entails 'particular downsides' ("particular" is to be taken literally, here ;-)
- homocysteine levels, mortality, cognitive impairment and more
- epigenetic programming by nicotine and different protein contents before birth
Can the backbone of bad triglycerides really be good for you?
Glycerol, a 3-carbon sugar alcohol that provides the backbone of triglycerides and is naturally found in foods as a component of dietary fats (Burke. 2011), is one of those supplements that have been all the rage for some time, didn't produce the expected instant results everybody was looking for (in this particlar case mostly "skinbursting pumps" and have eventually, in the course of one or two cycles of the regular yearly reformulations of the pre-workout supplements, completely disappeared from the market. I was therefore surprised, when I hit onto a recent study by researchers from the Physical Education and Sport High School in Konya (Turkey) that was published in one of the latest issues of the Journal of Human Kinetics (Patlar. 2012).
Is glycerol save? There have not been any reported toxicity effects up to doses of 5g/kg body weight. Glycerol does accumulates in body fluids, with the exception of the brain and the eyes and increases osmotic pressure (which was the reason why people used it in "pump supplements"), as well as the total volume of water in the body. If anything was 'dangerous', or I should probably rather say 'detrimental' to it, it would probably be its energy content (it is subject to gluconeogensis in the liver), which puts you at 'danger' of adding one or another pound of body fat you would probably want to avoid. The results of the study at hand to yet suggest that this is not an issue as long as you are active.In essence the study protocol is nothing extraordinary: Take a couple of guys, 40 in this case (age 22.82 ± 1.49 years), and feed and water them using...
- 1.2 g/kg body weight) followed by water (26 ml/kg body weight) to 10 sedentary individuals (GS) and 10 soccer players from the University team
- just plain water to the another 10 sedentary men and 10 soccer players
- Astrand Cycle Ergometer Test and an
- Wingate Anaerobic Power Test *the videos are don't show the study participants
What's a shuttle run? I guess those of you who play soccer or basketball will know similar drills (at least I have been tormented by my trainers with them before in both sports and could imagine they are also among the standard repertoire of football coaches - though I have never played that myself):Now if we take a look at the results of this undertaking they are unquestionably somewhat surprising - at least at first sight (see figure 1). In absolute terms it looks as if we had an across the board, almost identical increase in performance due to the daily shuttle runs in the exercise groups and a surprisingly large beneficial effect of glycerol only in the sedentary subjects (which would by the way be in line with many of the more or less disappointing trials on the benefits of glycerol supplementation in athletes; cd. Burke. 2011):
The shuttle run was followed by a couple of minutes of walking to cool down and a stretching exercise. The data was collected, logged and archived for evaluation.
"The subjects warmed up for several minutes by jogging followed by stretching. The test program was installed on the computer and initiated. A single beep was emitted at regular intervals. The subjects had to complete a lap or shuttle (foot on or over the line) with each beep. If the subjects completed a lap early they had to wait for the beep before starting the next lap. A triple beep indicated the start of a new level with a slightly faster speed required to complete each lap.
Video 1: The shuttle run is every trainer's darling and would actually make a nice conditioning workout to be implemented into your own routine - whatever it may you are training for (note: the video is a random pick from YouTube and has no relation to the study at hand).
The subjects were encouraged to complete as many levels as possible. An observer monitored the progress of a given subject, recording each completed lap on the recorder form. The subjects were instructed to turn by pivoting and not to run in a wide arc. The test was terminated when a subject was two or more steps from the line, for two consecutive laps. The observer alerted the subject at this time." (Patlar. 2012)
|Figure 1: Changes in anaerobic and aerobic performance - relative values on the left, absolute before (white) and after (black) on the right (Patlar. 2012)|
- the benefit the sedentary subjects derived from the supplementation looks even more pronounced,
- the aerobic performance of the soccer players in the exercise group did likewise benefit, albeit less than the performance of the sedentary group, and
- shockingly the increase in anaerobic performance which looks pretty much identical is not statistically significant, yet still reduced in the glycerol supplemented athletes in the exercise + glycerol group (note: there is an increase, it's only relatively smaller)
|Figure 2: Changes in body weight and relative power (watts per body weight) in the course of the trial (data based on Patlar. 2012)|
You cannot expect to lose weight, but surprisingly it may still happen that you do if you consume those 350kcal of glycerol with 2l water right before your daily shuttle run.
At least this is what happened to the soccer players in the supplementation group: They lost 2.66lbs of body weight on average. "Weight" is the unfortunate key word here, because we have no way of telling whether that was muscle, water or fat weight, as the scientists did not measure that separately. But let's be honest, it appears more than unlikely that it is (a) water or (b) muscle. After all the relative anaerobic power increased equally in both groups and why on earth would you lose water when you hyperhydrate? Ok, it could be one of those counter-regulatory reactions our bodies love. That again should however lead to performance decrements we did not see... you see, it's like the idiomatic dog that's chasing his tail. Why don't you play ginea pig and let us know what happens ;-)
WADA Warning for competitive athletes: If you are a WADA controlled athlete, you better avoid glycerol. It may sound hilarious, but it is on the WADA list of prohibited supplements since 2012. Why? Well, the increase in blood volume could mask the use of testosterone and co. because the /dl count would be lower if the total blood volume is higher -- this is something the WADA officials consider call a "masking agent" (Wada. 2012).
How much do you need? Don't forget, for glycerol to work its hyperhydrating magic, you must consume it with similarly hilarious amounts of water as the subjects in the study at hand. According to van Rosendal et al. an effective protocol comprises 1-1.5 g/kg glycerol + 25–35 ml/kg of ﬂuid. Assuming you weigh 80 kg you can't get way with anything below 80g of glycerol + 2l water! Obviously way more than what any of the hitherto no longer available 'pump' or pre-workout supplements contained (at least I have not come across one that has a 80g scoop and says "consume with at least 2l of water on the label" - have you?)Bottom line: I want to be honest, I still have to make up my mind about the usefulness of this supplement. I guess what actually does the trick is the combination of hyperhydration + energy availability. I have been preaching more than enough about the importance of energy availability over the last couple weeks, so I don't think I have to go into any more details here.
What I do think, however, is that few of you will be aware of the 2008 paper by Judelson et al. in which they report that hydration status is a fundamental determinant of the endocrine response to exercise, with dehydration leading to inappropriately high cortisol and norepinephrine levels that go hand in hand with an attenuation of the testosterone response to exercise, and negative effects on carbohydrate and lipid metabolism (Judelson. 2008).
Since you should by now have gotten the notion that insufficient energy does exactly the same, glycerol could well provide a means to counter this ergolytic double whammy. Against that background it is however strange that the athletes could not derive any athletic benefit from it... and weight loss without dieting (at least they were advised to stick to their habitual diets)?
If there is one definitive message you can take home from this study, though, it would be related to the dosage advice in the blueish info-box on the top right of this last paragraph: You better know how to use a supplement correctly! And this goes for the manufacturers of supps, as well as for the consumers: While the formers should finally stop putting ingredients into their supps to have them on the label, consumers should learn to identify hilariously underdosed and thus useless 'kitchen sink supplements' that 'have it all', but in doses where 'all' does not produce 'any' effect... how you can do that? Easy: Just make sure you get your daily dose of educative SuppVersity posts every day!
- Burke LM, Stear SJ, Lobb A, Ellison M, Castell LM. A-Z of nutritional supplements: dietary supplements, sports nutrition foods and ergogenic aids for health and performance--Part 19. Br J Sports Med. 2011 Apr;45(5):456-8.
- Judelson DA, Maresh CM, Yamamoto LM, Farrell MJ, Armstrong LE, Kraemer WJ, Volek JS, Spiering BA, Casa DJ, Anderson JM. Effect of hydration state on resistance exercise-induced endocrine markers of anabolism, catabolism, and metabolism. J Appl Physiol. 2008 Sep;105(3):816-24
- Patlar S, Yalcin H, Boyali E. The Effect of Glycerol Supplements on Aerobic and Anaerobic Performance of Athletes and Sedentary Subjects. Journal of Human Kinetics. 2012; 34: 69-70.
- Van Rosendal SP, Osborne MA, Fassett RG, Coombes JS. Guidelines for glycerol use in hyperhydration and rehydration associated with exercise. Sports Med. 2010 Feb 1;40(2):113-29.
- World Anti Doping Association. WADA Prohibited List 2010. < http://www.wada-ama.org/Documents/World_Anti-Doping_Program/WADP-Prohibited-list/2012/WADA_Prohibited_List_2012_EN.pdf > retrieved Nov. 01, 2012.