Does the use of dietary supplements enhance athletes’ sport performances? A systematic review and a meta-analysis

BACKGROUND: The consumption of dietary supplements has increased in recent years.\r\nDespite their widespread use, there is confusion about effects on sport performances.\r\nThe aim of this study was to investigate association between use of supplements and enhance of\r\nathletes’ sports performance.\r\nMETHODS: A review and a meta-analysis of studies conducted on Dietary Supplements and Sports\r\nbetween 2003 and 2013 were performed. Enhancement on sport performances was considered as\r\noutcome. The following aspects related to enhancement were considered: ergogenic effect (EE), time\r\nto exhaustion (TTE), muscular endurance (ME), post-exercise recovery (PER) and body mass (BM). With\r\nrespect to meta-analysis, data on level of post Exercise Glucose (GpE [mg/dL]) and level of post exercise\r\nLactate (LpE [mmol/L]) were considered as indicators of TTE, PER and EE. Similarly, Change in Body\r\nMass (CBM) [kg] was used as indicator of BM.\r\nRESULTS: The most investigated dietary supplements were: Creatine, Carbohydrates, Beta-alanine,\r\nProteins. The qualitative analysis evaluating the effect of supplements on sports listed by the\r\nInternational Olympic Committee has achieved interesting results: supplements didn’t show\r\nstatistically significant effects when compared to placebo in more than 48% of papers.\r\nFor the quantitative analysis, 15 studies were considered. The meta-analysis showed that there was\r\nno significant effect of Beta-alanine, Creatine and Carbohydrates on LpE and GpE. Furthermore, a nonsignificant\r\nincrease in BM was observed in athletes undergoing Creatine compared to placebo.\r\nCONCLUSION: Considering the increasing attention to this topic, it would be interesting to investigate\r\nthe existing awareness about effectiveness and possible risks of supplements.