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: 2.08). 12/2007; 21(4):1204-7. DOI: 10.1519/R-21226.1
Source: PubMed


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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    • "The prevalence of gastrointestinal (GI) discomfort may increase when ingesting low digestible CHO combined with exercise, resulting in a decrease in performance. A study examining the effects of raisins versus sports gels as pre-exercise feedings in cyclists showed no significant metabolic or performance differences during a 45-min sub-maximal cycling bout at 70%VO2max followed by a 15-min performance trial [10]. We know of no study to examine the effects of raisins versus commercial sports products in runners. "
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    ABSTRACT: We examined the metabolic, performance and gastrointestinal (GI) effects of supplementation with a natural food product (raisins) compared to a commercial product (sport chews). Eleven male (29.3 ± 7.9 yrs; mean and SD) runners completed three randomized trials (raisins, chews and water only) separated by seven days. Each trial consisted of 80-min (75%VO2max) treadmill running followed by a 5-km time trial (TT). Heart rate (HR), respiratory exchange ratio (RER), blood lactate, serum free fatty acids (FFA), glycerol and insulin, plasma glucose and creatine kinase, GI symptoms and rating of perceived exertion (RPE) were recorded every 20-min. We employed a within-subject two-way analysis of variance (ANOVA) for repeated measures with a Fisher's post hoc analysis to determine significant differences. VO2, HR, lactate, glycerol and RPE did not differ due to treatment. Average plasma glucose was maintained at resting levels (5.3 ± 0.4 mmol·L-1) during the sub-maximal exercise bout (5.9 ± 0.6, 5.7 ± 0.6 and 5.5 ± 0.5 mmol·L-1 for chews, raisins and water respectively), and was significantly higher with chews than water only. RER and % of non-protein macronutrient oxidation derived from carbohydrate was highest with chews, followed by raisins and water was the lowest (74.4 ± 6.4, 70.0 ± 7.0 and 65.1 ± 8.7% for chews, raisins and water respectively) during the sub-maximal exercise period. Serum FFA was higher in the water treatment versus both raisins and chews at 80 min of sub-maximal exercise. Serum insulin was higher with the chews than both raisins and water (5.1 ± 2.0, 3.1 ± 0.8, 1.9 ± 0.6 uU·ml-1 for chews, raisins and water respectively). Plasma creatine kinase, corrected for baseline values, for the last 40 min of the sub-maximal exercise bout, was higher with raisins compared to other treatments. The TT was faster for both carbohydrate supplements (20.6 ± 2.6, 20.7 ± 2.5, 21.6 ± 2.7 min for raisin, chews and water respectively). GI disturbance was mild for all treatments. Raisins and chews promoted higher carbohydrate oxidation and improved running performance compared to water only. Running performance was similar between the raisins and chews, with no significant GI differences.
    Journal of the International Society of Sports Nutrition 06/2012; 9(1):27. DOI:10.1186/1550-2783-9-27 · 1.91 Impact Factor
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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.
    Nutrition research 08/2010; 30(8):511-9. DOI:10.1016/j.nutres.2010.07.005 · 2.47 Impact Factor
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