Why do the ETT Athletes have fructose for breakfast on race day?
By Doug Stewart, Performance Director, and Rebecca Dent, Team Sports Dietitian
Before the Arc of Attrition by UTMB races in January, all four ETT athletes had a pretty similar breakfast: rice pudding with honey or syrup and an orange juice. Here, we look at why this works for endurance runners.
Kris (1st place male Arc25), Keith (3rd place male Arc50), Poppy (2nd place female Arc50) & Hugh (2nd place male Arc50) @Sportograf
Carbohydrate (carb) loading has been popular amongst endurance athletes for years. The link between carbohydrate consumption and endurance performance is well established in academic studies (Burke et al., 2011, Thomas et al., 2016). And, as the name of the meal suggests, breakfast is the first opportunity for athletes to break their overnight fast and have carbohydrates. This is very important as liver glycogen concentrations have been found to decrease by around 25% while we sleep (Iwayama et al., 201). Muscle glycogen remains relatively stable through the night; however, both liver and muscle glycogen levels are linked to endurance performance (Bergström et al., 2967, Casey et al., 2000).
Guidance for endurance athletes ranges from 1 to 4 g of carbohydrate per kilogram of body weight for the meal they have before their event (Burke et al., 2011, Thomas et al., 2016), which is most commonly breakfast. However, these guidelines did not advise on the best form of carbohydrate.
Following endurance exercise, co-ingesting fructose and glucose (versus only glucose) was found to enhance liver glycogen stores without negatively impacting muscle glycogen stores (Décombaz et al., 2011, Fuchs et al., 2016, Wallis et al., 2008). Based on this, Dr Tim Podlogar and colleagues (Podlogar et al., 2022) examined the impact of adding fructose at breakfast on subsequent endurance performance (compared to consuming only glucose based carbohydrates).
Their research study investigated the impact of a fructose-glucose breakfast on cycling endurance in 8 trained male cyclists. A double-blind crossover trial compared performance after consuming a breakfast of glucose and rice versus fructose and rice. The results indicated that the fructose and rice breakfast led to significantly improved endurance capacity. Notably, blood glucose, lactate levels, and substrate oxidation rates did not differ significantly between the two conditions.
Looking at the results, the time to task failure when taking glucose and rice was, on average, 130 minutes; whilst with the fructose and rice, the study participants lasted for 137 minutes on average. It is important to highlight that the total amount of carbohydrates consumed was identical for each participant in both trials. The only variance was swapping between glucose and fructose and the athletes did not know what breakfast they were having.
You can see on the chart below that 7 of the 8 participants improved their performance when taking the fructose and rice breakfast. However, one did get worse with the fructose and rice breakfast, and some only improved minimally.
Figure 1. Time to task failure during cycling following a breakfast containing GLU + RICE or FRU + RICE. Bars represents mean; circles and connecting lines represent individual participants (N = 8). Source Podlogar et al., 2022.
Therefore, there is some individual variance and it is advised that, if you are looking to try this type of breakfast out, you should practise with it in training. But, on average, the study suggests that fructose supplementation may enhance liver glycogen replenishment, leading to better endurance performance, although further research is needed to confirm the mechanisms and optimal fructose-glucose ratio.
The Elite Trail Team athletes will often have rice pudding for their race day breakfast with honey or agave syrup (both sources of fructose) and a glass of fruit juice (another source of fructose). Rice is a great source of carbohydrate, and by adding in some honey or syrup, plus fruit juice, they are ensuring they are having fructose to help replenish liver glycogen stores after these have been depleted through the night.
References
Bergström, J., Hermansen, L., Hultman, E., & Saltin, B. (1967). Diet, muscle glycogen and physical performance. Acta Physiologica Scandinavica, 71(2–3), 140–150. https://doi.org/10.1111/j.1748-1716.1967.tb03720.x
Burke, L.M., Hawley, J.A., Wong, S.H.S., & Jeukendrup, A.E. (2011). Carbohydrates for training and competition. Journal of Sports Sciences, 29(Suppl. 1), S17–S27. https://doi.org/10.1080/02640414.2011.585473
Casey, A., Mann, R., Banister, K., Fox, J., Morris, P.G., Macdonald, I.A., & Greenhaff, P.L. (2000). Effect of carbohydrate ingestion on glycogen resynthesis in human liver and skeletal muscle, measured by 13 C MRS. American Journal of Physiology-Endocrinology and Metabolism, 278(1), E65–E75. https://doi.org/10.1152/ajpendo.2000.278.1.E65
Décombaz, J., Jentjens, R., Ith, M., Scheurer, E., Buehler, T., Jeukendrup, A.E., & Boesch, C. (2011). Fructose and galactose enhance postexercise human liver glycogen synthesis. Medicine & Science in Sports & Exercise, 43(10), 1964–1971. https://doi.org/10.1249/MSS.0b013e318218ca5a
Fuchs, C.J., Gonzalez, J.T., Beelen, M., Cermak, N.M., Smith, F.E., Thelwall, P.E., Taylor, R., Trenell, M.I., Stevenson, E.J., & van Loon, L.J.C. (2016). Sucrose ingestion after exhaustive exercise accelerates liver, but not muscle glycogen repletion compared with glucose ingestion in trained athletes. Journal of Applied Physiology, 120(11), 1328–1334. https://doi.org/10.1152/japplphysiol.01023.2015
Iwayama, K., Tanabe, Y., Tanji, F., Ohnishi, T., & Takahashi, H. (2021). Diurnal variations in muscle and liver glycogen differ depending on the timing of exercise. The Journal of Physiological Sciences, 71(1), 35. https://doi.org/10.1186/s12576-021-00821-1
Podlogar, T., Cirnski, S., Bokal, Š., Verdel, N., & Gonzalez, J. T. (2022). Addition of Fructose to a Carbohydrate-Rich Breakfast Improves Cycling Endurance Capacity in Trained Cyclists. International Journal of Sport Nutrition and Exercise Metabolism, 32(6), 439-445. https://doi.org/10.1123/ijsnem.2022-0067
Thomas, D.T., Erdman, K.A., & Burke, L.M. (2016). Nutrition and athletic performance. Medicine & Science in Sports & Exercise, 48(3), 543–568. https://doi.org/10.1249/MSS.0000000000000852
Wallis, G.A., Hulston, C.J., Mann, C.H., Roper, H.P., Tipton, K.D., & Jeukendrup, A.E. (2008). Postexercise muscle glycogen synthesis with combined glucose and fructose ingestion. Medicine & Science in Sports & Exercise, 40(10), 1789–1794. https://doi.org/10.1249/MSS.0b013e31817e0f7e