Guidelines for daily carbohydrate intake: do athletes achieve them?

Department of Sports Nutrition, Australian Institute of Sport, Belconnen, ACT, Australia.
Sports Medicine (Impact Factor: 5.32). 02/2001; 31(4):267-99. DOI: 10.2165/00007256-200131040-00003
Source: PubMed

ABSTRACT Official dietary guidelines for athletes are unanimous in their recommendation of high carbohydrate (CHO) intakes in routine or training diets. These guidelines have been criticised on the basis of a lack of scientific support for superior training adaptations and performance, and the apparent failure of successful athletes to achieve such dietary practices. Part of the problem rests with the expression of CHO intake guidelines in terms of percentage of dietary energy. It is preferable to provide recommendations for routine CHO intake in grams (relative to the body mass of the athlete) and allow flexibility for the athlete to meet these targets within the context of their energy needs and other dietary goals. CHO intake ranges of 5 to 7 g/kg/day for general training needs and 7 to 10 g/kg/day for the increased needs of endurance athletes are suggested. The limitations of dietary survey techniques should be recognised when assessing the adequacy of the dietary practices of athletes. In particular, the errors caused by under-reporting or undereating during the period of the dietary survey must be taken into account. A review of the current dietary survey literature of athletes shows that a typical male athlete achieves CHO intake within the recommended range (on a g/kg basis). Individual athletes may need nutritional education or dietary counselling to fine-tune their eating habits to meet specific CHO intake targets. Female athletes, particularly endurance athletes, are less likely to achieve these CHO intake guidelines. This is due to chronic or periodic restriction of total energy intake in order to achieve or maintain low levels of body fat. With professional counselling, female athletes may be helped to find a balance between bodyweight control issues and fuel intake goals. Although we look to the top athletes as role models, it is understandable that many do not achieve optimal nutrition practices. The real or apparent failure of these athletes to achieve the daily CHO intakes recommended by sports nutritionists does not necessarily invalidate the benefits of meeting such guidelines. Further longitudinal studies of training adaptation and performance are needed to determine differences in the outcomes of high versus moderate CHO intakes. In the meantime, the recommendations of sports nutritionists are based on plentiful evidence that increased CHO availability enhances endurance and performance during single exercise sessions.

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    ABSTRACT: Trekkers exposed to prolonged hypobaric hypoxia commonly experience weight loss, especially loss of lean body mass (LBM). Evidence indicates that protein supplementation, specifically leucine, potentially attenuates loss of LBM in a catabolic state. This study investigated if leucine supplementation would prevent the loss of LBM during prolonged hypoxia. 18 trekkers (M=10 and F=8; age: 47.2 ± 11.5; range: 28-70y), completed a 13-day trek in Nepal from Lukla to Everest Base Camp. The participants were exposed to altitudes of 2810-5364m (mean 4140m). Participants consumed a 7.0g leucine supplement or an isocaloric, isonitrogenous placebo twice daily prior to meals. Body composition, body weight, and circumferences of bicep, thigh, and calf were taken pre and post trek. The participants from both treatments experienced significant loss of LBM and weight loss after 13 days at altitudes above 2810m (P< 0.05). However, there was no difference in loss of LBM (leucine -1.2 ± 1.6%; placebo -2.1 ± 1.5%) or body weight (leucine -2.2 ± 1.5%; placebo -2.3 ± 2.0%) or circumferences between the groups. Overall, our results indicate that under the conditions of this study, leucine did not significantly reduce LBM loss during 13 days of altitude-induced hypoxia. This study was funded by Glanbia Nutritionals.
    03/2013, Degree: Nutrition, MS (expected May 2013)
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    ABSTRACT: Carbohydrate (CHO) ingestion may be an interesting approach to avoid significant decrement to the tennis match performance. The aim of the present investigation was to assess the effects of CHO supplementation on tennis match play performance. Twelve young tennis players (18.0 +/- 1.0 years; 176 +/- 3.4cm; 68.0 +/- 2.3kg; body fat: 13.7 +/- 2.4%) with national rankings among the top 50 in Brazil agreed to participate in this study, which utilized a randomized, crossover, double blind research design. The experiment was conducted over a 5-day period in which each player completed two simulated tennis matches of a 3-hour duration. The players received either a CHO or a placebo (PLA) drinking solution during simulated tennis matches. Athlete's performance parameters were determined by filming each match with two video cameras. Each player was individually tracked for the entire duration of the match to measure the following variables: (1) games won; (2) rally duration; (3) strokes per rally; (4) effective playing time (%); (5) aces; (6) double faults; (7) first service in; (8) second service in; (9) first return in and (10) second return in. There were no differences between trials in any of the variables analyzed. CHO supplementation did not improve tennis match play performance under the present experimental conditions.
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    ABSTRACT: Loss of body weight and fat-free mass (FFM) are commonly noted with prolonged exposure to hypobaric hypoxia. Recent evidence suggests protein supplementation, specifically leucine, may potentially attenuate loss of FFM in subcaloric conditions during normoxia. The purpose of this study was to determine if leucine supplementation would prevent the loss of FFM in subcaloric conditions during prolonged hypoxia. Eighteen physically active male (n = 10) and female (n = 8) trekkers completed a 13-day trek in Nepal to Everest Base Camp with a mean altitude of 4140 m (range 2810-5364 m). In this double-blind study, participants were randomized to ingest either leucine (LEU) (7 g leucine, 93 kcal, 14.5 g whey-based protein) or an isocaloric isonitrogenous control (CON) (0.3 g LEU, 93 kcal, 11.3 g collagen protein) twice daily prior to meals. Body weight, body composition, and circumferences of bicep, thigh, and calf were measured pre- and post-trek. There was a significant time effect for body weight (-2.2% ± 1.7%), FFM (-1.7% ± 1.5%), fat mass (-4.0% ± 6.9%), and circumferences (p < 0.05). However, there was no treatment effect on body weight (CON -2.3 ± 2.0%; LEU -2.2 ± 1.5%), FFM (CON -2.1 ± 1.5%; LEU -1.2 ± 1.6%), fat mass (CON -2.9% ± 5.9%; LEU -5.4% ± 8.1%), or circumferences. Although a significant loss of body weight, FFM, and fat mass was noted in 13 days of high altitude exposure, FFM loss was not attenuated by leucine. Future studies are needed to determine if leucine attenuates loss of FFM with longer duration high altitude exposure.
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