SHEDDING NEW LIGHT ON CARBOHYDRATES AND EXERCISE

SHEDDING NEW LIGHT ON CARBOHYDRATES AND EXERCISE Dr Javier Gonzalez Department for Health, University of Bath, UK. j.t.gonzalez@bath.ac.uk

Van Loon (2012) Energy Stores FAT: >100,000 kcal

Van Loon (2012) Energy Stores FAT: >100,000 kcal CHO: <3,200 kcal

Oxidation rate (kj/min) Fuels for Exercise 100 75 Other lipid sources Plasma NEFA Plasma glucose Muscle glycogen (& plasma lactate) 50 25 0 Rest 40 55 75 Exercise intensity (% W max ) van Loon et al. (2001) J Physiol; Bosch et al. (1994) J Appl Physiol 76(6) Jeukendrup et al. (1999) Am J Phyiol 276(4); Jeukendrup et al. (1999) J Physiol 515(2)

Time to fatigue (hours) Muscle Glycogen & Endurance 5 4 3 Low CHO Mixed High CHO 2 1 0 0 100 200 300 Muscle glycogen (mmol/kg ww) Bergstrom et al. (1967) Acta Physiol Scand 71: 140

What about the Liver? Gonzalez et al. (2016) Am J Physiol 311: E543

Coyle et al. (1986) J Appl Physiol 61: 165 Carbohydrate Ingestion Liver

Time to fatigue (min) Casey et al. (2000) Am J Physiol Endocrinol Metab 287:E65x Liver Glycogen & Endurance 100 80 r = 0.53 p < 0.05 60 40 20-60 -40-20 0 20 40 60 Delta liver glycogen content (g)

Nutrition for performance

Types of Carbohydrate INTESTINAL LUMEN Glucose SGLT1 INTESTINAL CELLS Glucose GLUT2 BLOODSTREAM

Types of Carbohydrate INTESTINAL LUMEN Glucose Glucose Glucose Glucose Glucose Glucose SGLT1 INTESTINAL CELLS Maximum rate ~60 g/h (~1 g/min) Glucose BLOODSTREAM GLUT2

Types of Carbohydrate INTESTINAL LUMEN Glucose Fructose SGLT1 GLUT5 INTESTINAL CELLS Maximum rate ~105 g/h (~1.75 g/min) Glucose Fructose GLUT2 GLUT2 BLOODSTREAM

Maximizing Carbohydrate Delivery Maximal exogenous CHO oxidation: GLU ~1 g/min GLU + FRU 1.75 g/min SUC = GLU + FRU Liver Jeukendrup (2010) Curr Opin Clin Nutr Metab Care 13(4) Gray & Ingelfinger (1966) J Clin Invest 45(3) Wallis & Wittekind (2013) Int J Sport Nutr Exerc Metab 23(6)

But isn t fructose toxic? <5%E Egli et al. (2013) Diabetes 62: 2259

But isn t fructose toxic? <5%E 30%E Egli et al. (2013) Diabetes 62: 2259

But isn t fructose toxic? Egli et al. (2013) Diabetes 62: 2259 <5%E 30%E 30%E 208 g/d (41 tsp)

Participants Age: 25 ± 1 y VO 2 peak: 58 ± 1 ml/min/kg Wpeak: 330 ± 9 W Training volume: 12 ± 2 h/week

Study Design

Liver Glycogen MRS Scan

Muscle Glycogen

Study Design GLU or SUC or WAT (1.8 g/min) 600 ml 150 ml MRS Scan 0 30 60 90 120 150 Time (min) 180 MRS Scan Gonzalez et al. (2015) Am J Physiol Endocrinol Metab 309(12):E1032 = Douglas bag sample

Muscle glycogen concentration (mmol/l) Gonzalez et al. (2015) Am J Physiol Endocrinol Metab 309(12):E1032 Muscle Glycogen 150 Pre Post 100 50 0 WAT (n = 4) GLU (n = 14) SUC (n = 14)

Liver glycogen concentration (mmol/l) Liver Glycogen 500 Pre Post 400 300 200 100 0 WAT (n = 4) GLU (n = 14) SUC (n = 14) Gonzalez et al. (2015) Am J Physiol Endocrinol Metab 309(12):E1032

Intramyocellular lipid concentration (mmol/g) Intramyocellular Lipid 10 Pre Post No difference in net carbohydrate or fat utilisation in muscle 5 0 WAT (n = 4) Gonzalez et al. (2015) Am J Physiol Endocrinol Metab 309(12):E1032 GLU (n = 14) SUC (n = 14)

Blood lactate concentration (mmol/l) Blood Lactate 2.5 2.0 GLU SUC 1.5 1.0 0.5 0.0 0 30 60 90 120 150 180 Gonzalez et al. (2015) Am J Physiol Endocrinol Metab 309(12):E1032 Time (min)

Plasma NEFA concentration (mmol/l) Plasma NEFA 0.8 0.6 GLU SUC 0.4 0.2 0.0 0 30 60 90 120 150 180 Time (min)

Net substrate utilization (kj) Whole-body Substrate Utilization 10000 7500 FAT P = 0.02 FAT 5000 2500 CHO P = 0.01 CHO 0 GLU Gonzalez et al. (2015) Am J Physiol Endocrinol Metab 309(12):E1032 Trial SUC

Gut discomfort 6 Gut Discomfort 0 30 60 90 120 150 180 5 4 GLU SUC Sucrose reduces gut Time discomfort P < and 0.0001 RPE Trial NS Interaction P < 0.01 3 2 1 0 30 60 90 120 150 180 Gonzalez et al. (2015) Am J Physiol Endocrinol Metab 309(12):E1032 Time (min)

Carbohydrates During Exercise When ample CHO (>1 g/min) is provided: Carbohydrate ingestion prevents liver glycogen depletion during endurance exercise Sucrose ingestion increases whole-body carbohydrate utilization during endurance exercise, compared to glucose ingestion

Power output (W) What about Performance? 285 a b 270 255 240 225 210 a PLA Currell & Jeukendrup (2008) Med Sci Sports Exerc GLU GLU + FRU

CHO during recovery

Muscle Glycogen Repletion Betts & Williams (2010) Sports Med 40(11):941.

Liver Glycogen Repletion

Muscle glycogen concentration (mmol/l) Muscle Glycogen Recovery 175 150 125 Glucose Sucrose 100 75 50 25 Fuchs et al. (2016) J Appl Physiol 0 0 120 300 Time (min)

Liver glycogen content (g) Liver Glycogen Recovery 100 75 Glucose Sucrose # # 50 25 Fuchs et al. (2016) J Appl Physiol 0 0 120 300 Time (min)

Nausea (AU) Nausea 70 60 50 Glucose Sucrose # # 40 30 20 10 0 30 60 90 120 180 210 240 270 300 Fuchs et al. (2016) J Appl Physiol Time (min)

Carbohydrates for Recovery When ample CHO (>1.2 g/kgbm/h) is provided: Glucose-fructose mixtures accelerate liver, but not muscle glycogen repletion rates compared to glucose ingestion only Glucose-fructose mixtures result in less gut discomfort than glucose ingestion only

Unresolved questions What is the minimum amount of carbohydrate required to prevent liver glycogen depletion during exercise? What is the optimum amount and type of nutrition for post-exercise liver glycogen recovery? Gonzalez et al. (2016) Am J Physiol 311: E543

Summary Carbohydrate ingestion prevents liver glycogen depletion, maintains blood glucose concentration and carbohydrate oxidation Glucose-fructose mixtures increase carbohydrate availability and alleviate gut discomfort during exercise Glucose-fructose mixtures double liver glycogen repletion rates, relative to glucose only, with lower gut discomfort

Take Home Messages To maintain optimal endurance performance during prolonged, endurance-type exercise, consider ingesting a mixture of glucose + fructose (sucrose) at a rate of 30-90 g/h. To accelerate acute post-exercise recovery consider ingesting a mixture of glucose + fructose (sucrose) at a rate of 1.2 g/kgbm/h.

Acknowledgements