By James Collier BSc (Hons) RNutr, Nutrition Consultant
Not so long ago if you wanted to purchase a carbohydrate powder from a health food store it was easy, you simply bought glucose. But, as with all areas of sports nutrition, things have moved on and now there’s a range of different formulas. Use this article as a reference guide for which one suits different circumstances.
In order to understand the various carb supplements, it will be useful to understand a few terms first:
The simplest form of carbohydrate, i.e. one sugar molecule. Examples are glucose and fructose.
A carbohydrate compound made up of two sugars. Examples are sucrose (table sugar), lactose (milk sugar), and maltose.
Carbohydrate chain of a few simple sugars in length.
Carbohydrates containing a large number of sugars. Starch, glycogen, multidextrose, and cellulose are examples.
The following terms are relevant when evaluating the response to foods:
Glycaemic Index (GI)
This measures the reaction of the blood glucose levels to consuming a food when compared with glucose, which has a GI of 100. Low GI foods, below about 55 cause glucose levels in the blood to rise only slowly and over a long time period, compared with high GI foods of over 70, which lead to a rapid but short lived rise in blood glucose.
Insulin Index (II)
This describes the response of blood insulin (the hormone which regulates blood glucose levels) to consuming all foods; it is not just relevant to carbohydrate containing foods. Some meats and other low carbohydrate foods evoke an insulin response without a glycaemic response.
Glycaemic Load (GL)
This is a simple calculation based on the GI, but it also takes into account the amount of carbs contained in an average food portion. This gives us a relevant reference directly related to the actual amount of food we eat. For example the GI of watermelon is 72 so it is classed as a high GI food, but the GL of a ‘portion’ of watermelon, i.e. a large slice (120g) contains very few carbs and so when you calculate the GL it has a very low score of 4 (a GL score of 10 or less is low).
Glycaemic Response (GR)
This is the speed and level of blood sugar increase after eating food or a meal.
Carbohydrate Supplements Explained
Dextrose is simply glucose, the simplest carbohydrate. Dextrose is a monosaccharide which is 70-80% as sweet as table sugar. It is highly soluble in water and mixes easily with a fork or in a shaker. Dextrose has been used for decades in sports supplementation, and its use continues today. It has a GI of 100 and is used for energy or refuelling after a workout. It is available as a flavoured or unflavoured powder to be added to drinks. It is also increases the mixability of other substrates when combined in solution.
Maltodextrin, also known as multidextrose or glucose polymer powder, is a synthetic polysaccharide, i.e. a complex carbohydrate. It is usually produced from corn starch and the glucose polymers vary in length. It is a fine white powder which is not sweet, and is actually relatively bland.
Maltodextrin is used by a range of sports people to help meet the high-energy demands of intense exercise. Although structurally it is a ‘complex’ carbohydrate the chemical structure is such that it is open to rapid breakdown, so it is digested and absorbed very rapidly. It is infact digested faster than sugar and has a GI of 105. Its main uses are for additional energy, to help bodybuilders gain quality weight and for refuelling after exercise. It is commonly a primary ingredient in weight gain formulas as it’s a cheap and convenient way of bumping up the calories. It is also used as a clinical supplement in patients who have a poor appetite or high energy requirements.
There is considerable evidence indicating benefits to refuelling more efficiently by consuming high GI carbs post workout (Seiple, et al 1983; Gisolfi, et al 1992)), and some texts advocate a mixture of both maltodextrin and dextrose post workout. Maltodextrin and dextrose each have a different osmolarity so the rate they are emptied from the stomach differs, as does the rate they are absorbed in the intestine into blood following this. Furthermore there are two separate mechanisms for carbohydrate absorption in the intestine, one which absorbs carbohydrate as monosaccharides, and one which absorbs them as di- and oligosaccharides, and using both maltodextrin and dextrose post workout will maximise uptake by utilising both mechanisms independently. Shi et al (1995) demonstrated this by showing that a solution containing both of the substrates gave more carbohydrate uptake and better hydration following exercise.
Fructose is the monosaccharide found in most fruits and in honey. It has a GI of 40 so, despite being a simple carbohydrate, it is infact slowly absorbed. Fructose is a coarse granular powder with a sweet taste that mixes very well in water. It has been popular as a sweetener as gram for gram compared with sucrose (table sugar) it is a lot sweeter, therefore you need less and you consume less calories. Like dextrose, fructose also increases the mixability of other substrates when combined in solution. Fructose’s main use as a carbohydrate supplement is that it provokes an insulin response a lot less than dextrose or maltodextrin.
Palatinose is a low GI carbohydrate which provides a steady influx of glucose. It is a fine powder which has a very low GI of 32 and is also low on the II. It’s basically a source of glucose but without the surge of insulin, which makes it a useful supplement pre-exercise. It is much less sweet than sugar and is also heat stable, so can be used in cooking.
Activated barley is a pre-sprouted grain carbohydrate source that is digested slowly. The GI is very low at below 30 making it an ideal slow release energy source. It is also high in the soluble fibre beta-glucan which may have cholesterol-lowering and immune-enhancing benefits. The fibre forms a gelatinous medium which is slowly digested. This creates a stable, steady release of energy and nutrients. Other nutrients include high levels of antioxidants and omega-3 and omega-6 fatty acids.
Ultra Fine Ground Oats
Oats are a traditional food and a great source of slow released, low GI carbohydrate. You can, of course, buy your own oats and blend them to grind them but they aren’t soluble and produce a very gritty, not-so-pleasant shake. Ultra fine ground oats are available as a supplement, which retains the nutrition but makes oats soluble and more practical in a shake. All the nutrient benefits are retained, when the oats are ultra fine ground; this includes beta-glucan, the soluble fibre which is particularly good at helping to lower cholesterol levels, B vitamins and protein. However, the GI does increase; oats are low GI food around 55 (varies depending on type), but ultra fine ground oats have a higher GI (no figures available) and thus should be considered a medium GI carbohydrate source. They are still a nutritious source of carbohydrate though and typically work out cheaper than the other low GI carb powders.
Waxy Maize Starch (WMS)
Waxy maize starch is a complex, long-chain, super-high molecular weight carbohydrate with a neutral taste. WMS has a very high GI and very low osmolarity, so is absorbed extremely rapidly, quicker than maltodextrin, dextrose or even a combination of both. It is ideal for refuelling post workout and will boost insulin levels.
As WMS has a much higher molecular weight than dextrose and other carbs, it will pass through the stomach around 80% faster. This means it will also help hydration during exercise, as fluid will empty from the stomach more rapidly. WMS can easily be consumed directly before or even during workouts without upsetting your stomach. As WMS is absorbed so quickly, muscle glycogen levels will be replenished sooner when compared with glucose (up to 70% quicker), and with this it will also help pull more fluid into the muscles quicker, thus helping muscles to super-hydrate.
The polysaccharide which makes up WMS is primarily amylopectin at around 95-99% with amylose only 1-5% of the substrate. This is very different to ‘normal’ starch that we get in our food, which may be 20-25% amylose, depending on the plant. Amylopectin molecules are larger, heavier and easier for the stomach to digest and empty.
Vitargo is a patented carbohydrate formula derived from barley starch. The molecular weight of the molecules in Vitargo is a lot higher than other carbohydrates at around 500,000 to 700,000 compared to maltodextrin which is less than 10,000. The larger size minimises the osmolarity of Vitargo, so it can move through the stomach twice as fast as dextrose, so it’s absorbed a lot faster than most other carbs.
After training or competition Vitargo recovers muscle glycogen 68% faster (i.e. 50.2 compared to 29.9 mol glycosyl units/kgm) allowing for an increase in performance of up to 23% after just two hours, when compared to carbohydrates found in ordinary sport drinks (Piehl Aulin et al 1999).
A study by Stephens et al in 2007 found that the ingestion of Vitargo post workout resulted in faster and greater increases in blood glucose and serum insulin concentrations than a low molecular weight carbohydrate. Like WMS, it will empty from the stomach faster, and help with rehydration. It can be used pre- and during training without any discomfort and will help replenish glycogen more rapidly.
Trehalose is a disaccharide of glucose also known as mycose. It is abundant in nature and has been extracted from rye to be used as a food ingredient. It’s used in food processing in convenience meals as it helps stop moist foods from drying out. Although it has been sold as a sports supplement, there is little advantage to using it to improve performance and is unlikely to catch on.
D-Ribose is a pentose monosaccharide which occurs naturally in all living cells and is responsible for the onset of the metabolic process for ATP production. As a sports supplement the results from studies are very mixed, making it hard to conclude if ribose supplementation is worthwhile, thus I feel the jury is still out on this one. The evidence that ribose supplementation improves ATP production is reasonable, but the problem is this seldom translates into improved athletic performance.
Ribose has been shown to increase cellular energy stores and to maximise ATP stores as well as helping post workout recovery, but only at larger doses. 4g per day showed no beneficial impact on performance and muscle ATP recovery (Op’t Eijnde et al 2001); but with 10g per day ribose was shown to increase muscular strength and total work performed (Van Gammeren 2002).
Any possible benefits from supplementation with D-ribose are certainly more suited to power sports such as sprinting and weight lifting as opposed to longer distance running, football, rugby, etc. Ribose may also work synergistically with and enhance the benefits of creatine supplements, but this may only be due to the fact that simple sugars enhance the effects of creatine, and ribose is no more beneficial than others, see Creatine FAQs.
The benefits from ribose supplements aren’t conclusive, and I certainly don’t feel its use should be viewed in the same way as the other carb powders.
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