Article

Metabolic and performance effects of raisins versus sports gel as pre-exercise feedings in cyclists

Department of Exercise and Nutritional Sciences, San Diego State University, San Diego, California 92182, USA.
The Journal of Strength and Conditioning Research (Impact Factor: 1.86). 12/2007; 21(4):1204-7. DOI: 10.1519/R-21226.1
Source: PubMed

ABSTRACT Research suggests that pre-exercise sources of dietary carbohydrate with varying glycemic indexes may differentially affect metabolism and endurance. This study was designed to examine potential differences in metabolism and cycling performance after consumption of moderate glycemic raisins vs. a high glycemic commercial sports gel. Eight endurance-trained male (n = 4) and female (n = 4) cyclists 30 +/- 5 years of age completed 2 trials in random order. Subjects were fed 1 g carbohydrate per kilogram body weight from either raisins or sports gel 45 minutes prior to exercise on a cycle ergometer at 70% V(.-)O2max. After 45 minutes of submaximal exercise, subjects completed a 15-minute performance trial. Blood was collected prior to the exercise bout, as well as after the 45th minute of exercise, to determine serum concentrations of glucose, insulin, lactate, free fatty acids (FFAs), triglycerides, and beta-hydroxybutyrate. Performance was not different (p > 0.05) between the raisin (189.5 +/- 69.9 kJ) and gel (188.0 +/- 64.8 kJ) trials. Prior to exercise, serum concentrations of glucose and other fuel substrates did not differ between trials; however, insulin was higher (p < 0.05) for the gel (110.0 +/- 70.4 microU x ml(-1)) vs. raisin trial (61.4 +/- 37.4 microU x ml(-1)). After 45 minutes of exercise, insulin decreased to 14.2 +/- 6.2 microU x ml(-1) and 13.3 +/- 18.9 microU x ml(-1) for gel and raisin trials, respectively. The FFA concentration increased (+0.2 +/- 0.1 mmol x L(-1)) significantly (p < 0.05) during the raisin trial. Overall, minor differences in metabolism and no difference in performance were detected between the trials. Raisins appear to be a cost-effective source of carbohydrate for pre-exercise feeding in comparison to sports gel for short-term exercise bouts.

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    • "Raisins elicited similar metabolic responses after 45 minutes of exercise, with no difference in performance during a subsequent 15-minute exercise bout, as compared to a sports gel [52]. A human intervention study, published in 2 separate papers [36] [41], reported a trial where men (aged 50-70 years) and postmenopausal women were assigned to consume 160 g of raisins daily, increase the number of steps walked in a day, or a combination of both, for 6 weeks. "
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    ABSTRACT: The health benefits of grapes and wine have been studied and publicized extensively, but dried grapes (raisins, including "sultanas" and "currants") have received comparatively little attention. The purpose of the review was to summarize the polyphenol, phenolic acid, and tannin (PPT) composition of raisins; predict the likely bioavailability of the component PPT; and summarize the results of human intervention studies involving raisins. The most abundant PPTs are the flavonols, quercetin and kaempferol, and the phenolic acids, caftaric and coutaric acid. On a wet weight basis, some PPTs, such as protocatechuic and oxidized cinnamic acids, are present at a higher level in raisins compared to grapes. In human intervention studies, raisins can lower the postprandial insulin response, modulate sugar absorption (glycemic index), affect certain oxidative biomarkers, and promote satiety via leptin and ghrelin. However, only limited numbers of studies have been performed, and it is not clear to what extent the PPT component is responsible for any effects. More research is required to establish the bioavailability and health effects of the PPT component of raisins, the effects of raisins on health biomarkers in vivo in humans, and how these effects compare to grapes and wine.
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    ABSTRACT: Two studies were conducted to investigate gastrointestinal (GI) tolerance of high carbohydrate (CHO) intakes during intense running. The first study investigated tolerance of a CHO gel delivering glucose plus fructose (GLU+FRC) at different rates. The second study investigated tolerance of high intakes of glucose (GLU) vs. GLU+FRC gel. Both studies used a randomized, 2-treatment, 2-period crossover design: Endurance-trained men and women (Study 1: 26 men, 8 women; 37 +/- 11 yr; 73 +/- 9 kg; 1.76 +/- 0.07 m. Study 2: 34 men, 14 women; 35 +/- 10 yr; 70 +/- 9 kg; 1.75 +/- 0.09 m) completed two 16-km outdoor-runs. In Study 1 gels were administered to provide 1.0 or 1.4 g CHO/min with ad libitum water intake every 3.2 km. In Study 2 GLU or GLU+FRC gels were given in a double-blind manner to provide 1.4 g CHO/min. In both studies a postexercise questionnaire assessed 17 symptoms on a 10-point scale (from 0 to 9). For all treatments, GI complaints were mainly scored at the low end of the scale. In Study 1 mean scores ranged from 0.00 +/- 0.00 to 1.12 +/- 1.90, and in Study 2, from 0.00 +/- 0.0 to 1.27 +/- 1.78. GI symptoms were grouped into upper abdominal, lower abdominal, and systemic problems. There were no significant treatment differences in these categories in either study. In conclusion, despite high CHO gel intake, and regardless of the blend (GLU vs. GLU+FRC), average scores for GI symptoms were at the low end of the scale, indicating predominantly good tolerance during a 16-km run. Nevertheless, some runners (~10-20%) experienced serious problems, and individualized feeding strategies might be required.
    International journal of sport nutrition and exercise metabolism 10/2009; 19(5):485-503. · 1.98 Impact Factor
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