Can fructose make me faster?
Carbohydrates are king when it comes to endurance sports. Higher intakes of carbohydrate are associated with better performance. But can you push your limits by incorporating different types of carbohydrates into your race nutrition?
Fructose is a carbohydrate that can support increased fueling. If you are aiming for high carbohydrate consumption, fructose is an important part of your plan!
What is fructose?
Fructose is a monosaccharide (single sugar) that is the major carbohydrate present in fruit. It is absorbed directly into the blood during digestion. High fructose foods include apples, cherries, figs, mangos, pears, watermelon, sugar snap peas and honey. White sugar (or table sugar) is made up of one fructose plus one glucose unit.
How can fructose increase my fueling?
The main type of carbohydrate included in endurance nutrition is glucose. Your ability to absorb glucose is limited by the capacity of the glucose transport system within your gut. Fructose utilises a different transport mechanism, which can help you achieve increased fueling when combined with glucose. This means there is more carbohydrate available to exercising muscles and more carbohydrate burned so you can push harder!
What level of fueling requires the addition of fructose?
Similar to a blocked exit on the freeway, the glucose transport system will bank up if you consume more than it can transport per hour. Beyond 60g carbohydrate per hour, you should include fructose to keep the exits flowing, supporting high fuel use with less risk of gut issues.
Can fructose provide benefits outside of race nutrition?
Addition of fructose to a glucose-based carbohydrate source at breakfast has been shown to increase endurance capacity in a recent randomised controlled trial. Cyclists who consumed glucose + fructose exercised for 7 minutes longer than those who consumed glucose only in a time to failure trial. Cereal with fruit is a quick, easy pre-exercise meal containing glucose plus fructose.
Eating carbohydrate foods increases your blood glucose and insulin level. Some people experience transient, rebound hypoglycaemia (drop in blood glucose level) after exercise has started. This may cause short-term fatigue and weakness and impair performance. Including fructose in your pre-exercise meal or snack can reduce your risk of rebound hypoglycaemia at the start of exercise.
Including fructose in your recovery nutrition can accelerate glycogen repletion (carbohydrate stored in muscle and liver). This is useful to rebuild fuel stores if you have <24h before your next exercise session. Fructose can also lower the risk of gut symptoms if you consume large amounts of carbohydrate during recovery.
How can I be sure I am including adequate glucose and fructose?
Some sport nutrition products list the percentage of glucose:fructose in a 2:1 ratio. Sucrose (table/white sugar) is 1:1 glucose:fructose. Australian honeys usually contain 36-50% fructose, 28-36% glucose and 1-5% sucrose, depending on the floral source. The quantity of fructose in fruit varies. Trialing fructose containing fueling options in training is your best way to know what level of fructose supports performance whilst minimising gut issues.
Are there any side effects from fueling with fructose?
About 30% of people don’t absorb fructose very well. If you are prone to exercise-associated gut symptoms, it is best to avoid high fructose foods and drinks. You do not need to completely avoid fructose however. Foods that contain glucose in amounts equal to or greater than fructose are usually well-tolerated. Training regularly with a high carbohydrate intake may also reduce gut issues.
Including fructose before, during and after exercise supports high fuel use, can reduce gut issues and improve performance. Fructose-containing foods include fruit, white sugar, honey and specialised sports nutrition products. Be sure to trial fructose in training to know if it is right for you!
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Fuchs CJ., Gonzalez JT & van Loon LJC 2019, 'Fructose co‐ingestion to increase carbohydrate availability in athletes', Journal of Physiology, vol. 597, iss. 14, pp. 3549–3560.
Okano G et al 1988, 'Effect of pre-exercise fructose ingestion on endurance performance in fed men', Medicine and Science in Sports and Exercise, vol. 20, iss.2, pp. 105-109.
Podlogar T. et al 2022, 'Addition of Fructose to a Carbohydrate-Rich Breakfast Improves Cycling Endurance Capacity in Trained Cyclists', International Journal of Sport Nutrition and Exercise Metabolism, vol. 32, iss. 6, pp. 439-445.