ORIGINAL ARTICLE Effects of a high-carbohydrate versus high-protein meal on acute responses to hypoxia at rest and exercise Keyne Charlot • Aure ´lien Pichon • Jean-Paul Richalet • Didier Chapelot Received: 28 May 2012 / Accepted: 28 July 2012 Ó Springer-Verlag 2012 Abstract A carbohydrate (CHO) solution consumed before exposure to hypoxia has been reported to reduce arterial oxygen desaturation at rest. The purpose of this study was to determine whether this effect occurred during exercise and when the CHO load is part of a meal. Eleven male subjects (mean age 20.1 ± 1.8 years, BMI 24.3 ± 2.4 kg m 2 ) consumed either a high-CHO (2,340 kJ, 70 % CHO, 12 % protein) or an isoenergetic high-protein (35 % CHO, 48 % protein) breakfast meal 60 min before being exposed to 15 min of hypoxia (F I O 2 = 13.5 %) followed by 30 min of exercise in hypoxia (60 % of _ V O 2max ). Sat- uration of oxygen via a pulse oxymeter (SpO 2 ), ventilatory parameters, substrate oxidation, interstitial glucose con- centrations, and heart rate variability (HRV) were moni- tored continuously during the whole session. Results showed no effect from the type of meal on SpO 2 at rest but a 3.1 ± 0.4 % reduction of desaturation during exercise (P \ 0.005) compared to the high-protein version. This was associated with higher levels of ventilation (P \ 0.05) and CO 2 production (P \ 0.01). Glucose oxidation was higher after the high-CHO than the high-protein breakfast over the whole session (?19.4 ? 4.0 %, P \ 0.0001), whereas the interstitial glucose levels were increased only at rest (P \ 0.001). HRV indices were not different between conditions. In conclusion, a high-CHO meal consumed prior to moderate exercise in hypoxia condition reduced oxygen desaturation compared to a high-protein meal. Keywords Hypoxia  Carbohydrate  Exercise  Meal  Oxygen saturation  Heart rate variability  Continuous glucose monitoring Introduction Improving tolerance to hypoxia is a constant concern for people who must be exposed to high altitude and some recent results suggest that dietary choices may represent an efficient strategy. It has actually been shown that ingesting a carbohydrate (CHO) solution during an acute exposure to hypoxia increased arterial oxygen saturation (SaO 2 ) (Lawless et al. 1999). More recently, it was reported that drinking a glucose solution 40 min prior to hypoxia exposure was followed by higher oxygen saturation mea- sured by pulse oximetry (SpO 2 ) (Golja et al. 2008; Kle- menc and Golja 2011), CO 2 production and ventilation ( _ V E ) (Golja et al. 2008) compared to an equal volume of water. These results suggest that ingested CHO may con- tribute to improved physiological tolerance to hypoxia through increased O 2 transport and delivery to the tissues. CHO would enhance the production of CO 2 (Ferrannini 1988) which in turn would stimulate _ V E . However, this effect seems to last only during the metabolism of the ingested CHO (Golja et al. 2008) and would require spreading intake over the whole period of exposure. It remains to be determined whether this response to hypoxia observed with a CHO solution may occur when CHO is consumed as part of a meal. An increase in oxygen Communicated by Guido Ferretti. K. Charlot  A. Pichon  J.-P. Richalet  D. Chapelot (&) EA2363, Laboratoire des Re ´ponses Cellulaires et Fonctionnelles a ` l’Hypoxie, UFR SMBH, Universite ´ Paris 13, Sorbonne Paris Cite ´, 74 rue Marcel Cachin, 93017 Bobigny Cedex, France e-mail: dchapelot@gmail.com J.-P. Richalet Service de Physiologie, Explorations Fonctionnelles et Me ´decine du Sport, AP-HP, Ho ˆpital Avicenne, Bobigny, France 123 Eur J Appl Physiol DOI 10.1007/s00421-012-2472-z