TYPES OF SUGAR
The recommendation in recent years has been for endurance athletes in events >2 hours duration with high carbohydrate needs (>60g/hour) should consume multiple transportable carbohydrate during exercise in a 2:1 glucose:fructose ratio. Fructose has a different transport system for absorption from the intestine, so adding some fructose to the glucose consumed allows a greater amount of carbohydrate to be absorbed by the body. An increasing number of people are being identified as fructose malabsorbers, and trying to increase fructose as a fuel option for exercise may be problematic in terms of gut comfort. Fructose malabsorption may be exacerbated with exercise due to increased irritation of the gut, even though there may not be any gastrointestinal symptoms day-to-day. So it comes down to looking at maximizing carbohydrate intake within individual tolerance levels and exercise needs.
NATURAL SUGARS VS REFINED
Some endurance athletes have taken an interest in ‘natural’ forms of carbohydrate and sugars as an alternative to formulated sports products eg. gels. This involves preparing home-made snacks rather than relying on commercial sports nutrition products. As per my recent blog post, natural sugars are not always as innocent as they may seem, and are not necessarily healthier than refined sugar. I am all for reducing intake of processed food and additives across the board, but when it comes to athletic performance we really need to think about the type of individual sugars from a more scientific perspective. Home-made cookies, balls and cakes are terrific, and there are a range of sweet and savoury options that work well. The only problem is that many natural sugars are often high in fructose, which can cause major gut issues for long-duration exercise. Natural options are often low glycemic index, which means they may be more slowly digested….great if you are trying to lose weight and need help staying full for longer but not so great if you want food to empty rapidly from the stomach while exercising. Finding the right balance of carbohydrates takes planning, and also some trial and error. If you are set on going all natural then go for it, but if your gut is telling you ‘no’ then you may need to mix it up a bit. Pre- and post-exercise is where unrefined carbohydrates come into their own, but during exercise the focus should be on glucose vs fructose rather than natural vs processed.
DO ATHLETES REALLY NEED ALL THAT CARBOHYDRATE?
There is so much discussion about carbohydrate as a fuel, but cyclists certainly don’t need to be carbohydrate loading for every session. There are potential benefits of training with low fuel stores for selected training sessions to encourage physiological adaptations that optimize fuel systems. In reality, a competitive situation may lead to low carbohydrate stores with limited carbohydrate availability, so an improved ability to rely on fat oxidation for fuelling may be of benefit. Some athletes are following the low carb trends and there is a movement by some ultra-endurance athletes to train their bodies to use predominantly fat as a fuel, replacing gels and bars with tubes of nut butter to fuel exercise. Fat is a slow-burning fuel, so although this approach may work well for some individuals, to truly maximize endurance performance, sugar throughout will help. Numerous studies show that faster finish times for endurance athletes correlate with higher carbohydrate intake during an event– if you can use more carbohydrate you can move faster. However if your exercise is of shorter duration, you won’t need to be so aggressive with carbohydrate intake. If you are not sure how much carbohydrate you need, speak with an Accredited Sports Dietitian to tailor your intake.
Athletes trying to lose weight often reduce carbohydrates. This can be an effective strategy, but it is important to be selective about where in the day carbohydrates are reduced and by how much, with the priority to time carbohydrate for training needs to produce the best training outcomes and adaptations. There has been recent interest in ‘train-low’ and ‘sleep-low’ concepts of carbohydrate timing, which may improve fuel utilization but may also be appropriate to support body fat goals.
Dental health is often compromised in athletes. With reduced saliva production during exercise, coupled with high sugar intake and the acidity of most sports drinks, the teeth of an athlete are constantly at risk. Dental problems are the result, so it is wise to try to reduce the contact of sugars with your teeth and try to get plenty of water rinses to reduce the risk of tooth damage.
Sure, carbohydrates are beneficial for performance, but this doesn’t mean you have to be on a constant carbohydrate load. The type, timing and amount will vary according to specific exercise requirements, gastrointestinal tolerance and personal preference. Choosing natural sugars is not necessarily better for during endurance activity. Work on finding the right mix for your individual needs.
Jeukendrup, A (2011) 'Nutrition for endurance sports: marathon, triathlon, and road cycling' JSpSci
Stellingwerff, T & Cox, G (2014) 'Systematic review: carbohydrate supplementation on exercise performance or capacity of varying durations' ApplPhysNutrMetab
Lisa Middleton is one of Australia’s most experienced Sports Dietitians. Lisa has spent over 15 years advising some of the nation’s most elite athletes and teams across a range of sports including VIS athletes, the Essendon, Hawthorn and St Kilda AFL Football clubs, Melbourne Vixens Netball, Melbourne Storm Rugby League and Melbourne Victory Football clubs throughout grand final and premiership years.