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Glucose, Fructose and Galactose - Oh My! Which Sugar Makes the Best Sports Drink?
By Rick Morris
While a lot of science and research goes into the formulation of your favorite sports or carbohydrate replacement drink, the sports beverages themselves remain very simple. Nearly every carbohydrate replacement sports drink is a combination of water, sugar and electrolytes. There are a lot of choices in specific formulations, but not in the actual ingredients.
The first part of your sports drink potion is water. Not many choices there! I You can probably choose between purified water, tap water or spring water. Other than that, water is water. How about the electrolytes. The most important ones are sodium, potassium and chloride. Every popular sports beverage will at least have sodium. Some others may add other types of electrolytes and maybe some vitamins. But still not a lot of choices here.
Now we get to the final part of the sports drink potion - sugars. This is really what carbohydrate replacement sports drinks are all about. Getting those valuable carbohydrates back into your body. Sports drink makers use one or more of several types of sugars to replace your lost carbohydrates. Which type of sugar is best for replacing your lost carbohydrates, extending your running endurance and improving your running performance? The best place to start answering that question is with a brief overview of the six types of sugars.
There are two categories of sugars - monosaccharides and disaccharides. The difference is that monosaccharides are single sugar units and disaccharides are two single sugar units linked together. Monosaccharides tend to be absorbed and become available as an energy source more quickly because you can absorb them directly into your blood stream. Disaccharides must first be digested before they can be used to produce energy. This distinction becomes important when choosing the best sugar for your sports drink.
The three most important monosaccharides are glucose, a simple sugar made by plants and fructose the sugar in fruit. The third is galactose, a part of milk sugar. The three most important disaccharides are sucrose or table sugar, a combination of glucose and fructose; lactose or milk sugar, a combination of glucose and galactose; and maltose or malt sugar, a combination of two glucose sugars.
The vast majority of carbohydrate replacement sports drinks use glucose, fructose or a combination of the two - sucrose. Another common sugar source is high fructose corn syrup which is sometimes called sucrose syrup because it is also a combination of glucose and fructose. Other carbohydrate sources sometimes used include the complex carbohydrate maltodextrin and natural sources such as brown rice syrup and cane juice.
I know what you're thinking. All this info is great but I still don't know which sugar is best for my sports drink. Let's start with what you don't want. There has been a lot of press lately on the benefits of milk, particularly chocolate milk, as a recovery drink. Studies have shown that milk is a very effective running and sports recovery drink. I've tried it and I agree - milk is great for recovery. But using it for a hydration or a carbohydrate replacement drink either during or before your run may not be a great idea. Not only can the fat content in milk cause a delay in gastric emptying, not to mention an upset stomach, the galactose in milk may actually cause a decrease in your running performance. A study done at the Institute of Food, Nutrition and Human Health in New Zealand looked at the affect of the milk sugar galactose on endurance cycling performance. They concluded that "Ingestion of an 8% galactose-only solution is detrimental to endurance performance compared with equivalent volumes of iso-osmotic solutions containing 50% galactose/50% glucose or 80% glucose/20% fructose. This may reflect the inability of the liver to convert galactose into glucose at a rate required to support strenuous exercise intensity."
That leaves us with glucose, fructose or a combination of the two. Almost every study agrees that both glucose and fructose, taken alone, provide similar benefits to endurance athletes, but recent data suggests that fructose may help reduce perceived exertion. An investigation at Lakehead University in Ontario found that "...fructose and glucose are of equal value in prolonging exercise time to exhaustion in endurance cycling. Ingesting fructose before and during exercise apparently provided a more constant supply of glucose to be available to the working muscles. The more stable blood glucose levels with fructose ingestion may be beneficial in reducing perceived exertion and thereby allowing for an enhancement in exercise performance.
If one sugar is good will two be better? In many cases two will be better. A recent study looked at the affects of combining glucose and fructose in a sports drink. In other words using good old fashioned table sugar. These researchers said "Ingestion of GH (glucose/fructose combination) led to an 8% improvement in cycling time-trial performance compared with ingestion of glucose (glucose only)."
The bottom line is that both glucose and fructose will do a good job of replacing your lost carbohydrates and improving your running endurance but combining the two together may improve your running performance even more. Should you always go with the glucose/fructose combination? The simplest sugar of all is glucose. It enters your blood stream directly without the need to be digested. The combination of glucose and fructose forms sucrose, a disaccharide, which is a more complex sugar that must be digested before it can be used to produce energy. Because it's a more complex carbohydrate, the glucose/fructose combination will help keep a smooth constant supply of energy to your muscles, making it ideal for moderate to long runs. But if you need quick energy like at the end of a marathon or long training run, the quick energy of glucose might be more beneficial.
Here are my suggestions for carbohydrate sources in your carbohydrate replacement drink.
Sugar Type Uses
Quick energy at the end of your marathon or long training run.
Good alternative to glucose for most training runs because it is a simple sugar that is absorbed directly but still provides some stable energy flow benefits.
Sucrose (Glucose/Fructose Combination) Great for pre run hydration and during moderate to long races or runs
Not suggested for use before or during your run. Can be a effective as a recovery drink.
Superior endurance performance with ingestion of multiple transportable carbohydrates, Med Sci Sports Exerc, 2008 Feb;40(2):275-81
Comparison of fructose and glucose ingestion before and during endurance cycling to exhaustion, J Sports Med Phys Fitness, 2000 Dec;40(4):343:9
The effect of galactose supplementation on endurance cycling performance, Eur J Clin Nutr., 2009 Feb;63(2):209-14
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