Beverage Acceptability and Fluid Intake During Exercise - Book Report/Review Example

Running head: BEVERAGE ACCEPTABILITY AND FLUID INTAKE DURING EXERCISE Impact of beverage acceptability on fluid intake during exercise halima.tabani.m05 [Institute's Name] Running head: BEVERAGE ACCEPTABILITY AND FLUID INTAKE DURING EXERCISE 18th March 2009 halima.tabani.m05 [Course] Running head: BEVERAGE ACCEPTABILITY AND FLUID INTAKE DURING EXERCISE 18h March 2009 Impact of beverage acceptability on fluid intake during exercise The following paper discusses the article "Impact of beverage acceptability on fluid intake during exercise" by D.H. Passe et al. (2000) and critically appraises it. The paper is divided into five main sections viz. introduction, methodology, results, discussion (including strengths and weaknesses) and conclusion. Each section in this paper discusses the strengths and weaknesses of the respective sections in the article followed by suggestions for improvement, where required. INTRODUCTION The authors of this study have provided a fairly good introduction and background to the study. They have initially discussed the need to maintain the body fluid balance at all times as one of the principal homeostatic mechanisms of the human body and that this maintenance is of vital importance during exercise via fluid replenishment, in order to overcome inadvertent fluid losses and to restore the normal body fluid balance (ACSM, 1995; Gisolfi & Dutchman, 1992; Murray, 1987 cited in Passe et al, 2000:219). They further discuss that the phenomenon of voluntary dehydration was first observed and elucidated in adults several decades ago and has more recently been discerned in children too. However, they did not define the term voluntary dehydration adequately. Greenleaf and Sargent (1965:719) defined the term voluntary dehydration as 'the delay in complete rehydration following water loss' (Greenleaf & Sargent, 1965) and this phenomenon is of prime concern in individuals involved in vigorous physical activity including athletes, military personnel, etc . Hypohydration, on the other hand, has been defined as 'the state of decreased water content while the osmotic concentration of the body is maintained (Greenleaf & Sargent, 1965:719). Several studies have investigated the factors which influence the severity of voluntary hydration and it has been shown that cool water, as opposed to warm water and addition of flavor and carbohydrate electrolyte components were important factors which contributed towards an increased fluid intake thereby reducing the severity of voluntary dehydration (Rothstein et al., 1947, Sohar et al., 1962, Wilk et al., 1996 and 1998 cited in Passe et al, 2000:219). Since the main focus of this study is the impact of hedonic value of a beverage on its consumption, the authors describe the concept of hedonic value, as being a sensory measure of liking and discuss the studies conducted previously in this regard, highlighting their important findings (Hubbard et al., 1984; Wilmore et al., 1998 cited in Passe et al, 2000:220). Since conflicting views exist on the use of the terms such as acceptability and palatability, the authors have discussed the different views. For this study, the authors have taken both these terms to be used interchangeably and have used a pre-validated 9 point scale for the measurement of hedonic value as done previously by Cardello (1996) and suggested by Yeomans (1998) (Cardello 1996; Yeomans 1998 cited in Passe et al, 2000:220) The authors proposed that although several studies have investigated the factors influencing voluntary fluid intake during exercise, relationship of the qualities and composition of the beverage and the taste preference of the individuals with intake of a particular beverage, there are no existing studies which have investigated the impact of hedonic value of a beverage on its voluntary consumption and its relationship with exercise. An extensive literature showed that this was indeed the case. Therefore, the objectives of this study were to investigate the effect of the hedonic value of beverages on voluntary fluid consumption and also the impact that exercise had on the sensory experience of beverages. These objectives are well defined and focused. METHOD The study was carried out by means of two experiments carried out two months apart. The first experiment was designed to identify the most acceptable (M) and least acceptable beverage (L) from a choice of 10 different commercially available beverages, for each study participant. The subsequent experiment then explored the effect of exercise on the voluntary fluid intake and whether it influenced the perception and acceptability of the beverage. The study participants for experiment 1 comprised of 49 triathletes and runners with similar baseline characteristics while for experiment 2, forty participants from the previous experiment and nine new participants were enrolled. The study sample was appropriately chosen as the phenomenon of voluntary dehydration is most applicable to athletic individuals and rehydration through voluntary fluid intake becomes of prime importance. The standard deviation from the mean for all baseline characteristics (i.e. age, training hours per week and athletic events per year) was low; therefore, there were no significant differences in the baseline characteristics of study participants which could lead to variability of the results. This study sample however, had the limitation of having a male to female ratio of approx. 2:1. This could have been improved by taking an equal number of males and females so that any differences in results occurring due to gender differences could be accounted for. Other limitations were that proper inclusion and exclusion criteria for the study participants were not described and 9 participants in the second experiments were new recruits. The study design i.e. experimental trial was well chosen. All the environmental and study variables were standardized and well controlled for, including the composition of the beverages, exercise settings and conditions, temperature and humidity of the study environment. Measures such as using 11 X 11 Latin square arrangement were undertaken to control for position effects. This helped in controlling the confounding effect of any of these variables on the results. The dependant and independent variables were predefined which helped in establishing a cause-effect relationship between the variables. The outcome variables measured included voluntary fluid intake, perceived intensities of sweetness, sample acceptability (hedonic value), leg and mental fatigue, lightheadedness and alertness. Appropriate statistical tests were applied to analyze the results i.e. percentages, means and standard errors for continuous variables, comparison of means via ANOVA, Duncan Multiple Range testing when required and p-values of less than 0.05 and 0.01 were taken to be significant. The sample size however, was compromised as it was calculated using an assumption of one way ANOVA analysis although the study involved a repeated measures design. Therefore, apart from some limitations, the methodology was well structured in order to achieve the objectives. RESULTS The results showed that during sedentary testing, the acceptability for the most acceptable flavor was significantly higher than that of water (W), which was in turn more acceptable than the least acceptable flavor. However, these findings changed during exercise testing, in which water had a lower acceptability score as compared to the most and least acceptable beverages and the most acceptable beverage was of superior acceptability than the least acceptable one, at the end of 90 and 180 min. Other important findings were that when the test condition changed from sedentary to exercise, the acceptability for L increased significantly but did not vary with the duration of exercise. On the other hand, the acceptability for M and W decreased during exercise condition. It was also shown that the percentage of subjects reporting light headedness and fatigue was higher for W. An unusual finding was that of a significant effect of beverage on perceived alertness with greater levels of alertness for M and L as compared to W. It was also noticed that the overall intake of M was higher than that of L and both were greater than that compared to W. The results of this study adequately addressed the objectives and the findings are in conformation with the hypothesis of the study. DISCUSSION The results of this study show that the voluntary intake of fluid is influenced by its hedonic value and this value changes under different conditions varying significantly between sedentary and exercise settings. Similarly several studies have shown that hedonic shifts do occur during exercise leading to an increase in the perception of pleasantness or acceptability of the food or beverage but the underlying mechanisms have not been established (Lluch, 1998; Lesham, 1999; Horio, 1998 cited in Passe et al, 2000:226). Although different mechanisms for a physiological basis for this phenomenon of hedonic shift have been proposed, there is no clear cut evidence as to what leads to this shift. Horio and Kawamura proposed the existence a possible feedback mechanism to the taste system which leads to this shift but the evidence is limited (Horio, 1998 cited in cited in Passe et al, 2000:226). On the other hand, Mack (1998) postulated that beverage hedonics and dipsogenic factors are the determinants of voluntary fluid intake but these two factors have been found to have overlapping features and thus are hard to distinguish. Several studies have shown palatability to be linked to appetite which is in turn linked to food intake but the physiological basis of palatability is complex and has been underexplored (Yeomans 1998 cited in Passe et al, 2000:226). Experimental studies and animal models have investigated the role of opiods in the modulation of palatability and as a result it has been postulated that palatability is influenced by endogenous opiods peptide activity (Cooper, 1983 and 1989; Yeomans, 1991 cited in Passe et al, 2000:226) It has also been proven the exercise affects the levels of opiods in the peripheral circulation (Schwarz, 1992; Thoren, 1990 cited in Passe et al, 2000:226) and thus it can be hypothesized that exercise induced changes in the levels of opiod peptides lead to a hedonic shift while exercising. However, more extensive research on this subject is required. This study showed that the intake of M and L was significantly greater than that of W in both the experiments. An important confounding factor which was not considered in many previously conducted studies on voluntary fluid intake was the use of a monadic procedure. The argument against the use of such a procedure is that underlying thirst sensations and other factors such as dry mouth during exercise may prompt the intake of an unacceptable beverage which happens to be the only one available and thus the intake of that beverage becomes obligatory. This factor was controlled for in this study by using a two-choice procedure which offers the subject a choice between the most and least favorable drinks hence adding to the strength of the study findings. The study also proves that flavored drinks are preferred over water during exercise and similar findings have been observed by Sohar (1962), Hubbard (1984) and Szlyk (1989) previously (Sohar, 1962; Hubbard,1984; Szlyk 1989 cited in Passe et al, 2000:227). The finding in this study that the intake of most acceptable beverage is greater as compared to the least acceptable one is consistent with the findings of Wilmore et al (1998). Therefore, this study not only confirms the findings of previously conducted studies but also improves upon the existing literature and adds new information regarding the subject. Strengths This study is the first study of its kind which specifically addresses the relationship between hedonic value of beverages and their intake. It has several advantages over other studies. Firstly, the composition of all the beverages used in this study was similar and standardized. This helps in establishing that the results were indeed due to the effect of hedonic value on fluid intake rather than due to other confounding variables such as nutritionally mediated post-ingestion effects, or the mechanical effects of carbonation. Furthermore, this study had an advantage of having a larger sample size as compared to other studies and so the effect sizes for different variables were found to be significant. Moreover, the assessment of palatability during both exercise and under sedentary conditions made it possible to assess the hedonic shift that occurred between these two conditions. Since independent variables were predetermined a causal and temporal relationship can be established between acceptability and fluid intake. Limitations Other than the limitations in methodology addressed previously, there are certain other limitations of this study. Firstly, since only 6% carbohydrate- electrolyte drinks were used in this study, the findings cannot be generalized to beverages of other categories and compositions. Similarly, since the study sample was limited to athletes performing a particular kind of activity, the question of whether the findings of this study are applicable to athletes of involved in different levels and kinds of activities/exercise and to other groups of people, e.g. those involved in laborious tasks and military personnel, still remains unanswered. CONCLUSIONS In light of the findings of this study, it can be concluded that beverage hedonic value (acceptance) and the state of exercise have significant influence on the voluntary intake of beverages with acceptance for less acceptable beverages increasing during exercise states. Moreover, it is also proposed that use of carbohydrate-electrolyte drinks during exercise is beneficial as compared to water but further research to explore this arena is required. List of references American College of Sports Medicine (ACSM) (1995). ACSM's guidelines for exercise testing and prescription, 5th edn. Baltimore: Williams and Wilkins cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:219 Cardello, A.V. (1996). 'The role of the human senses in food acceptance.' In H.L. Meiselman & H.J.H. MacFie (Eds), Food choice, acceptance and consumption. Pp. 182. London: Blackie Academic and Professional cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:220 Cooper, S.J. (1983). 'Suppression of saccharin-induced drink- ing in the non-deprived rat by low dose diazepam treatment.' Pharmacology, Biochemistry and Behavior 18, 825 827 cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:226 Cooper, S.J. & Turkish, S. (1989). 'Effects of naltrexone on food preference and concurent behavioral responses in food-deprived rats.' Pharmacology, Biochemistry and Behavior 33, 1720 cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:226 Gisolfi, C.V. & Duchman, S.M. (1992). ,Guidelines for optimal replacement beverages for different athletic events.' Medicine and Science in Sports and Exercise 24, 679-687 cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:219 Greenleaf, J.E. & Sargent, F. (1965). 'Voluntary dehydration in man'. Journal of Applied Physiology 20, 719-724 cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:219 Hubbard, R.W., Sandick, B.L., Matthew, R.P., Francesconi, R.P., Sampson, J.B., Durkot, M. et al. (1984). 'Voluntary dehydration and alliesthesia for water.' Journal of Applied Physiology: Respiratory, Environmental and Exercise Physiology 57, 868-873 cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:219 Horio, T. & Kawamura, Y. (1998). 'Influence of physical exercise on human preferences for various taste solutions.' Chemical Senses 23, 417421 cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:226 Leshem, M., Abutbul, A. & Eilan, R. (1999). 'Exercise in- creases the preference for salt in humans.' Appetite 32, 251260 cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:226 Lluch, A., King, N.A. & Blundell, J.E. (1998). 'Exercise in dietary restrained women: no effect on energy intake but change in hedonic ratings.' European Journal of Clinical Nutrition 52, 300307 cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:226 Mack, G.W. (1998). 'Recovery after exercise in the heat: factors influencing fluid intake.' International Journal of Sports Medicine 19, S139S141 cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:226 Murray, R.M. (1987). 'The effects of consuming carbohy drate-electrolyte beverages on gastric emptying and fluid absorption during and following exercise.' Sports Medicine 4, 322-351 cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:219 Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:219 Rothstein, A., Adolf, E.F. & Wills, J. H. (1947). Voluntary dehydration. In E.F. Adolf (Ed.), Physiology of man in thedesert. Pp. 254270. New York: Interscience Publishers cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229: 219 Schwarz, L. & Kindermann, W. (1992). 'Changes in _-endorphin levels in response to aerobic and anaerobic exercise.' Sports Medicine 13, 2536 cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:226 Sohar, E., Kaly, J. & Adar, R. (1962). The prevention of voluntary dehydration. In Symposium on environmental physiology and psychology in arid conditions. Pp. 129-135. Paris: United Nations Educational Scientific and Cultural Organization cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:219 Szlyk, P.C., Sils, I.V., Francesconi, R.P., Hubbard, R.W. & Armstrong, L.E. (1989). 'Effects of water temperature and flavoring on voluntary dehydration in men.' Physiology and Behavior 45, 639647 cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:227 Thoren, P., Floras, J.S., Hoffmann, P. & Seals, D.R. (1990). 'Endorphins and exercise physiological mechanisms and clinical implications.' Medicine and Science in Sports and Exercise 22, 417428 cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:226 Wilk, B. & Bar-Or, O. (1996). 'Effect of drink flavor and NaCl on voluntary drinking and hydration in boys exercising in the heat'. Journal of Applied Physiology 80, 1112-1117 cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:219. Wilk, B., Kriemler, S., Keller, H. & Bar-Or, O. (1998). 'Consistency in preventing voluntary dehydration in boys who drink a flavored carbohydrate-NaCl beverage during exercise in the heat.' International Journal of Sport Nutrition 8, 1-9 cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:219 Wilmore, J.H., Morton, A.R., Gilbey, H.J. & Wood, R.J. (1998). Role of taste preference on fluid intake during and after 90 min of running at 60% of VO2max in the heat. Medicine and Science in Sports and Exercise 30, 587595 cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:219 Yeomans, M.R. & Wright P. (1991). 'Lower pleasantness of palatable foods in nalmefene-treated human volunteers.' Appetite 16, 249259 cited in Passe D.H., Horn M. and Murray R. (2000) 'Impact of beverage acceptability on fluid intake during exercise' Appetite 35, 219-229:226 Yeomans, M.R. (1998). 'Taste palatability and the control of appetite.' Proceedings of the Nutrition Society 57, 609615 cited in Passe D.H., Horn M. and Murray R. 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