Genuine advances in sports nutrition are a bit like honest politicians, good food at motorway service stations and white Christmases: rare enough to count on the fingers of one hand.
However, the discovery that using two types of carbohydrate sugars (glucose and fructose) in a carbohydrate drink resulted in better performance was a genuine advance. Compared to glucose-only drinks, adding fructose increases the maximum rate of energy absorption during exercise, and so helps to stave off fatigue more effectively.
It’s hardly surprising, then, that these so-called 2:1 glucose/fructose drinks have become extremely popular among endurance athletes.
However, while the scientific evidence in favour of these 2:1 drinks is convincing, some researchers have been looking at whether glucose/fructose drinks can be made even better by manipulating the ratio of glucose to fructose to improve absorption (and performance) even further. And now a new study by New Zealand scientists indicates that indeed they can.
In the study, scientists looked at the effects of different ratios of glucose and fructose on the rate of carbohydrate and fluid absorption in 12 cyclists on four separate occasions – and how much of the ingested carbohydrate drink was subsequently used to provide energy during a repeated cycling task. The task consisted of a two-hour ride at 57 per cent of each cyclist’s maximum power output followed by 10 sprints.
During the task, the cyclists consumed 200ml of artificially sweetened water (the placebo) every 15 minutes or one of three glucose-fructose mixtures:
- Two parts glucose to one part fructose (2:1 – a similar composition to most commercially available mixed carbohydrate drinks);
- 1.25 parts glucose to one part fructose;
- 0.8 parts glucose to fructose (ie 1.25 parts fructose to one part glucose).
- Importantly, all three drinks contained the same total carbohydrate at the same concentration – it was only the glucose-fructose ratio that was altered.
In a nutshell
The first main finding was that when the cyclists drank the 1.25-parts-glucose-to-one-part-fructose drink, they were able to derive 18 per cent more energy for exercise from the carbohydrate consumed, compared to when they drank the conventional 2:1 glucose/fructose drink.
The 0.8-parts-glucose-to-fructose drink was also superior to the 2:1 drink – the cyclists who drank this derived 13 per cent more energy for exercise. More importantly perhaps, the cyclists’ sprint performances at the end of the two-hour ride were around three per cent better when they had been consuming the 1.25-parts-glucose-to-one-part-fructose beverage than when they drank either of the other drinks.
It’s early days but these results seem to provide convincing evidence that while 2:1 glucose-fructose carbohydrate drinks are superior to conventional glucose-only drinks, a 1.25:1 glucose/fructose ratio could bring even greater benefits.
A drink that provides 18 per cent more energy to the cycling muscles is not to sniffed at, as it means than less energy needs to be supplied from the muscles’ own glycogen reserves, which should help stave off fatigue and prolong endurance.
If the results are confirmed by other studies, look out for a new breed of carbohydrate drink appearing in shops soon! Med Sci Sports Exerc. 2013 Sep;45(9):1814-24
This article was first published in the October 10 issue of Cycling Weekly. Read Cycling Weekly magazine on the day of release where ever you are in the world International digital edition, UK digital edition. And if you like us, rate us!