Effect of graded fructose coingestion with maltodextrin on exogenous 14C-fructose and 13C-glucose oxidation efficiency and high-intensity cycling performance.
The ingestion of solutions containing carbohydrates with different intestinal transport mechanisms (e.g., fructose and glucose) produce greater carbohydrate and water absorption compared with single-carbohydrate solutions. However, the fructose-ingestion rate that results in the most efficient use of exogenous carbohydrate when glucose is ingested below absorption-oxidation saturation rates is unknown. Ten cyclists rode 2 h at 50% of peak power then performed 10 maximal sprints while ingesting solutions containing (13)C-maltodextrin at 0.6 g/min combined with (14)C-fructose at 0.0 (No-Fructose), 0.3 (Low-Fructose), 0.5 (Medium-Fructose), or 0.7 (High-Fructose) g/min, giving fructose:maltodextrin ratios of 0.5, 0. 8, and 1.2. Mean (percent coefficient of variation) exogenous-fructose oxidation rates during the 2-h rides were 0.18 (19), 0.27 (27), 0.36 (27) g/min in Low-Fructose, Medium-Fructose, and High-Fructose, respectively, with oxidation efficiencies (=oxidation/ingestion rate) of 62-52%. Exogenous-glucose oxidation was highest in Medium-Fructose at 0.57 (28) g/min (98% efficiency) compared with 0.54 (28), 0.48 (29), and 0.49 (19) in Low-Fructose, High-Fructose, No-Fructose, respectively; relative to No-Fructose, only the substantial 16% increase (95% confidence limits +/-16%) in Medium-Fructose was clear. Total exogenous-carbohydrate oxidation was highest in Medium-Fructose at 0.84 (26) g/min. Although the effect of fructose quantity on overall sprint power was unclear, the metabolic responses were associated with lower perceptions of muscle tiredness and physical exertion, and attenuated fatigue (power slope) in the Medium-Fructose and High-Fructose conditions. With the present solutions, low-medium fructose-ingestion rates produced the most efficient use of exogenous carbohydrate, but fatigue and the perception of exercise stress and nausea are reduced with moderate-high fructose doses.
Rowlands
David S
DS
Institute of Food, Nutrition, and Human Health, Massey Univ., Wellington, New Zealand. d.s.rowlands@massey.ac.nz
Thorburn
Megan S
MS
Thorp
Rhys M
RM
Broadbent
Suzanne
S
Shi
Xiaocai
X
D000284:Administration, Oral; D000328:Adult; D054874:Athletic Performance; D001628:Beverages; D001639:Bicarbonates / Q000097:blood; D001786:Blood Glucose / Q000378:metabolism; D001835:Body Weight; D001944:Breath Tests; D002247:Carbon Isotopes; D002250:Carbon Radioisotopes; D003085:Colic / Q000517:prevention & control; D018592:Cross-Over Studies; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D004573:Electrolytes / Q000097:blood; D004734:Energy Metabolism / Q000187:drug effects*; D005632:Fructose / Q000008:administration & dosage* / Q000378:metabolism; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D018763:Muscle Fatigue / Q000187:drug effects*; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D009325:Nausea / Q000517:prevention & control; D010084:Oxidation-Reduction; D010807:Physical Endurance; D011134:Polysaccharides / Q000008:administration & dosage* / Q000378:metabolism; D011594:Psychometrics; D013649:Taste; D013997:Time Factors; D014554:Urination
D001639:Bicarbonates; D001786:Blood Glucose; D002247:Carbon Isotopes; D002250:Carbon Radioisotopes; D004573:Electrolytes; D011134:Polysaccharides; D005632:Fructose; D019344:Lactic Acid; C008315:maltodextrin