Athletes advised not to use or ingest glycerol
Pending further clarification from WADA, ASADA recommends that athletes do not ingest or use glycerol, for example, for hyper-hydration. The WADA List Committee considers Glycerol as a masking agent within section S5 of the Prohibited List. Update WADA 2010
Effects of hypoosmolality on whole-body lipolysis in man.
Bilz S; Ninnis R; Keller U. Department of Research, University Hospital Basel, Switzerland. Metabolism 1999 Apr; 48(4): 472-6 PMID: 10206440 UI: 99221281
Changes in extracellular osmolality, and thus in the cellular hydration state, appear to directly influence cell metabolism. The metabolic changes associated with cell swelling are inhibition of glycogenolysis, glycolysis, and proteolysis. Recent studies in our laboratory demonstrated diminished whole-body protein breakdown in humans during an acute hypoosmolar state. Because of the close interrelationship between carbohydrate and fat metabolism, we speculated that adipose tissue lipolysis and fatty acid oxidation are regulated by changes in extracellular osmolality. Therefore, we investigated the effect of artificially induced hypoosmolality on whole-body lipolysis and fat oxidation in seven healthy young men. Hypoosmolality was induced by intravenous administration of desmopressin, liberal ingestion of water, and infusion of hypotonic (0.45%) saline solution. Lipolysis was assessed by a stable-isotope method (2-[13C]-glycerol infusion). The glycerol rate of appearance (Ra), reflecting whole-body lipolysis, was higher under hypoosmolar compared with isoosmolar conditions (2.35+/- 0.40 v 1.68+/-0.21 micromol/kg/min, P=. 03). This was even more pronounced when lipolysis was suppressed during hyperinsulinemia and euglycemic clamping (0.90+/-0.08 v 0.61+/-0.03 micromol/kg/min, P=. 002). However, plasma free fatty acid (FFA), glycerol, ketone body, insulin, and glucagon concentrations and carbohydrate and lipid oxidation measured by indirect calorimetry were not significantly altered by hypoosmolality. Plasma norepinephrine concentrations were lower under hypoosmolar conditions (P<. 01 v control). In conclusion, hypoosmolality in vivo results in increased whole-body lipolysis, which is not due to changes in major lipolysis regulating hormones.
Hyperhydrating with glycerol: implications for athletic performance.
Wagner DR. Exercise and Sports Science Department, Vanguard University of Southern California, Costa Mesa 92626, USA. J Am Diet Assoc 1999 Feb; 99(2): 207-12 PMID: 9972189 UI: 99138136
Small decreases in hydration status can result in a dramatic decrement in athletic performance and greatly increase the risk of thermal injury. Because of its osmotic properties, which enable greater fluid retention than the ingestion of water alone, glycerol has been proposed as a hyperhydrating agent. In fact, glycerol is now commercially available and marketed as a sport supplement to be ingested with water or sport drinks; thus, dietitians need to be cognizant of this new addition to the sports nutrition table. The results of glycerol-induced hyperhydration research have been equivocal, most likely because of methodologic differences between studies, such as variations in the intensity of exercise, environmental conditions, and concentration or dose of glycerol administered. Although the suggested dosage of glycerol depends on body size and varies between manufacturers, 1 g/kg body weight with an additional 1.5 L fluid taken 60 to
120 minutes before competition is standard. Some test subjects reported feeling bloated or nauseated after ingesting glycerol. This review examines glycerol-induced hyperhydration research and the safety of ingesting glycerol, discusses commercial availability of glycerol, and makes recommendations for glycerol-induced hyperhydration research.
Plasticising effect of water and glycerin on human skin in vivo.
Pedersen LK; Jemec GB. Dept. of Dermatology D, Bispebjerg Hospital, University of Copenhagen, Denmark. J Dermatol Sci 1999 Jan; 19(1): 48-52 PMID: 9890375 UI: 99105381
Application of water and glycerin is known to influence skin mechanics. The kinetics of these processes are of great interest. A study was performed to show the immediate changes in skin-mechanics. A Dermaflex machine (R) was used to study 23 healthy volunteers. Water or glycerin was applied to the flexorside of the forearm, and readings were made after 3, 6, 9, 12 and 15 min. Regional untreated skin served as baseline. In agreement with earlier studies both substances influenced hysteresis. Water caused a significant increase in hysteresis after 12 and 15 min of hydration (P<0.01). Glycerin caused significantly increased hysteresis after 3 min (P<0.05) and the effect continued to the end of the observation period. No significant differences were seen in the distensibility. The onset of action is rapid for both substances, and the effects are therefore supposed to take place in the outermost layers of epidermis. The effect of glycerin on the hysteresis is more rapid in onset than that of water. Comparing the permeability coefficients, the effect on the mechanical properties of the skin does not appear to be determined by the permeability coefficients as water has a higher permeability coefficient but induces smaller changes than glycerin. Water alone does not appear to be the optimal plasticiser of human skin and other substances soluble in both water and lipids may have an even greater influence on skin mechanics in vivo.
The effect of glycerol and desmopressin on exercise performance and hydration in triathletes.
Inder WJ; Swanney MP; Donald RA; Prickett TC; Hellemans J. Department of Endocrinology, Christchurch Hospital, New Zealand. Med Sci Sports Exerc 1998 Aug; 30(8): 1263-9 PMID: 9710867 UI: 98376726
BACKGROUND: Hydration is an important determinant of athletic performance, and glycerol-containing solutions have been demonstrated to produce a state of hyperhydration. Secretions of arginine vasopressin (AVP) and/or other renal mechanisms may account for reduced urine output following glycerol ingestion. This study examined the effect of glycerol and the AVP analog desmopressin (DDAVP) on hydration and exercise performance in triathletes ingesting routine volumes of prerace fluids.
METHODS: Eight male triathletes ages 19 to 43 participated. After determination of their VO (2peak), each athlete completed a strenuous exercise protocol three times involving 60 min of exercise at 70% VO (2peak) followed immediately by an incremental increase in workload every 2 min until exhaustion.
RESULTS: Pretreatment with 1 gxkg(-1) glycerol or 20 microgram of DDAVP intranasally failed to produce hyperhydration or any enhancement of athletic performance. There was a significant difference in reduction in body mass between DDAVP and control (P < 0.05) but no change in sweat volume. No physiologically relevant differences in plasma sodium, renin, or hemoglobin were seen with either active agent. Plasma osmolality did have a different time course in response to exercise following glycerol (P < 0.03) owing to a smaller incremental increase. Urine osmolality was also raised at baseline following glycerol (P < 0.05). Responses to exercise of plasma AVP, cortisol, and indices of carbohydrate metabolism were similar, although AVP was elevated following DDAVP administration (P < 0.01) owing to assay cross- reactivity.
CONCLUSION: Although maintaining adequate hydration remains important for the endurance athlete, the routine use of either glycerol of DDAVP before athletic training or competition in a thermoneutral environment does not seem to confer any advantage over conventional fluid replacement.
Modification of stratum corneum quality by glycerin- containing external ointments
Gloor M; Bettinger J; Gehring W. Hautklinik am Klinikum, Stadt Karlsruhe gGmbH. Hautarzt 1998 Jan; 49(1): 6-9 PMID: 9522186 UI: 98182654
The effects of glycerol are discussed in detail. Glycerol can lead to a transition of crystalline lipid structures within the horny layer lipids into liquid crystalline states. Especially if applied in oil/water-emulsions it improves the hydration of the horny layers better than urea. In addition, if facilitates the dissolution of desmosomes within the superior layers of the horny layer enhancing desquamation. Furthermore, by using glycerol, the mechanical properties of the skin can be influenced; long term used leads to increased elasticity. The roughness of the horny layer is reduced, which can be explained by the abrasive and/or the hydrating effect. Glycerol used in o/w-emulsions also protects against the influence of tensides or noxious lipophilic agents. Presumably a flux from the base of the epidermis towards its surface triggers the regeneration of the barrier. Finally, glycerol can lead--similarly to ureaˇto an improvement in active agent penetration, as has been proven for hexylnicotinate.
Pre-exercise glycerol hydration improves cycling endurance time.
Montner P; Stark DM; Riedesel ML; Murata G; Robergs R; Timms M; Chick TW. Department of Medicine, Veterans Affairs Medical Center, Albuquerque, NM 87108, USA.
Int J Sports Med 1996 Jan; 17(1): 27-33 PMID: 8775573 UI: 96371750
The effects of glycerol ingestion (GEH) on hydration and subsequent cycle ergometer submaximal load exercise were examined in well conditioned subjects. We hypothesized that GEH would reduce physiologic strain and increase endurance. The purpose of Study I (n = 11) was to determine if pre-exercise GEH (1.2 gm/kg glycerol in 26 ml/kg solution) compared to pre-exercise placebo hydration (PH) (26 ml/kg of aspartame flavored water) lowered heart rate (HR), lowered rectal temperature (Tc), and prolonged endurance time (ET) during submaximal load cycle ergometry. The purpose of Study II (n = 7) was to determine if the same pre-exercise regimen followed by carbohydrate oral replacement solution (ORS) during exercise also lowered HR, Tc, and prolonged ET. Both studies were double-blind, randomized, crossover trials, performed at an ambient temperature of 23.5-24.5 degrees C, and humidity of 25-27%. Mean HR was lower by 2.8 +/- 0.4 beats/min (p = 0.05) after GEH in Study I and by 4.4 +/- 1.1 beats/min (p = 0.01) in Study II. Endurance time was prolonged after GEH in Study I (93.8 +/- 14 min vs. 77.4 +/- 9 min, p = 0.049) and in Study II (123.4 +/- 17 min vs. 99.0 +/- 11 min, p = 0.03). Rectal temperature did not differ between hydration regimens in both Study I and Study II. Thus, pre-exercise glycerol-enhanced hyperhydration lowers HR and prolongs ET even when combined with ORS during exercise. The regimens tested in this study could potentially be adapted for endurance activities.
Failure to reduce body water loss in cold-water immersion by glycerol ingestion.
Arnall DA; Goforth HW Jr. Northern Arizona University, Flagstaff 86011. Undersea Hyperb Med 1993 Dec; 20(4): 309-20 PMID: 8286985 UI: 94115252
The efficacy of ingesting an aqueous glycerol solution to enhance body water retention during prolonged cold-water dives was evaluated. Nine Naval Special Warfare divers performed a 3-h dive in 13 degrees C water. Divers were assigned to either a water-treatment group (WT) or a glycerol-treatment (GT) group. WT ingested 30 ml water/kg lean body mass (LBM). GT ingested a solution consisting of 1.2 ml glycerol/kg LBM and 30 ml water/kg LBM. Blood was drawn at prehydration, 90 min after hydration, and 20 min after the 3-h dive for serum glycerol, glucose, free fatty acids, lactate, and electrolyte determinations. Fluid intake and output was recorded and urine analyzed for osmolality, electrolytes, and specific gravity. Serum glycerol values in GT were 200 times greater at posthydration than prehydration and 100 times greater at postdive than at prehydration. Urine output, total body weight loss, and non-urine weight loss during posthydration and dive sampling periods were not significantly different between treatment groups. Hyperhydration with an aqueous glycerol solution of 1.2 ml glycerol/kg LBM seems ineffective in significantly reducing body water loss in divers during prolonged cold-water immersion.
The influence of a single application of different moisturizers on the skin capacitance.
Loden M; Lindberg M. Medical Department, ACO AB, University Hospital, Uppsala, Sweden. Acta Derm Venereol 1991; 71(1): 79-82 PMID: 1676227 UI: 91281370
Moisturizers are believed to improve the skin condition by increasing the water content of the stratum corneum. A variety of techniques for assessing skin hydration has been developed. In the present study the capacitance following a single application of different moisturizers to normal skin on 12 volunteers was measured with the commercial available Corneometer 420. The moisturizers were pure petrolatum and three oil-in- water creams. The latter contained glycerine, glycerine and pyrollidone carboxylic acid, or urea as humectant agents. The first measurement of the change in the capacitance was done 2 h after application of the products. All tested products increased the capacitance in the same order of magnitude. For the creams the values were significantly enhanced during the experimental period (6 h). Excess products were removed from some skin areas after the 2 h measurement. This caused immediately a significant decrease in the capacitance of the cream treated sites, whereas tendencies towards higher values were noted on the petrolatum-treated sites. These findings indicate that the non-absorbed components influence the capacitance values. Hence, the interpretation of electrical measurements with respect to skin moisture should be made with caution.
Effect of a new amino acid solution in the oral hydration of nursing infants with acute diarrhea. A prospective study
Velasquez-Jones L; Mota-Hernandez F. Servicio de Hidratacion Oral, Hospital Infantil de Mexico Federico Gomez. Gac Med Mex 1990 Jul- Aug; 126(4): 315-22; discussion 322-3 PMID: 2093568 UI: 91235895
Thirty-two one- to 12-month-old male infants with diarrheal dehydration treated with either the oral rehydration solution recommended by the World Health Organization (WHO), or the same solution modified by the addition of glycerine (60 mmol/L) and glycil-glycine (30 mmol/L), with a total osmolality of 379 mOsm/kg. The patients belonging to the latter group exhibited greater stool losses (10.3 +/- 8.3 vs 8.0 +/- 6.4 mL/kg/hour) and a greater urine volume (10.4 +/- 14.2 vs 4.6 +/- 4.0 mL/kg/6 hours), during the first four to six hours of the rehydration period. The results of this study show, that in contrast with those of other series, the addition of glycine and glycil-glycine to the WHO solution, at the concentrations used in the study, produces greater fecal water losses in children with dehydration due to acute diarrhea.
The kinetics of swelling in muscle exposed to hypertonic glycerol solution.
Hummel Z. Department of Biophysics, University Medical School, Pecs, Hungary. Physiol Chem Phys Med NMR 1988; 20(3): 241-7 PMID: 3266674 UI: 89221307
In frog skeleton muscle treated with glycerol, the efflux of the slow potassium fraction is four times faster than the hydration of macromolecules being a little faster than the total swelling process. The slow K fraction is assumed to exist in special salt linkages called intra- and intermolecular K bridges for describing the correlation between the solubilization of proteins and K release. Conformational change involving helix-coil transition and cooperative effects in the K release could produce together the time-lag between the efflux of slow K fraction and swelling of the muscle.
Glycerol dynamics in weight-losing cancer patients.
Eden E; Edstrom S; Bennegard K; Lindmark L; Lundholm K. Surgery 1985 Feb; 97(2): 176-84 PMID: 4038560 UI: 85115955
This study was designed to show whether weight-losing cancer patients have an elevated glycerol turnover. Four groups of patients were examined: weight-losing cancer patients, weight-losing patients without cancer, cancer patients without weight loss, and weight-stable and well- nourished hospitalized control patients. Glycerol was infused intravenously at three different rates (200, 400, and 800 mumol/hr/kg body weight) after an overnight fast. This allowed measurement of clearance and plasma glycerol turnover. Weight-losing cancer patients (group 1) had an almost threefold higher glycerol turnover per kilogram of body weight compared with malnourished and well-nourished noncancer patients. However, both malnourished cancer and noncancer patients had an elevated glycerol turnover compared with well-nourished patients when glycerol turnover was related to whole body lipids. The results how that progressive clinical cancer is associated with an elevated plasma glycerol turnover, probably indicating an increased whole body lipolysis. This may explain the loss of body fat during the development of cancer cachexia.
Body weight: reduction by long-termglycerol treatment.
Wirtshafter D; Davis JD. Science 1977 Dec 23; 198(4323): 1271-4 PMID: 929200 UI: 78054759
Elevation of body glycerol concentration by multiple daily injections of glycerol was shown to lead to hypophagia and body weight loss followed by normal food intake and normal rate of body weight increase in rats. Termination of injections was followed by hyperphagia and an accelerated rate of growth. These findings suggest that the blood glycerol concentration plays an important role in the control of body weight and may be one signal by which the central nervous system monitors body lipid content.