Every so often there’s lots of buzz around an exciting new fueling product for athletes that has a revolutionary formula or ingredient that’s definitely going to dramatically improve your performance.
The new product is often launched with claims that the formulation optimises the delivery of energy to your body, perhaps through the slow-release of more complex carbs, or by speeding up the rate at which the products are processed by your gut.
‘SuperStarch’. ‘Cluster Dextrin™’. ‘Hydrogel technology’. You’ve probably come across words like these in marketing campaigns in recent years and on gel and drink mix packaging. As you’ll see later in this post, some deliver on their claims better than others.
But, does the type of carbohydrate in your gel, bar, chew or drink really matter all that much?
Does the type of carb matter?
In short, kinda, and in some specific scenarios it might matter more than in others. But generally only once you’ve first considered two far more important things....
1. How much carbohydrate you need per hour
This is the backbone of any decent fueling strategy; is it meeting your energy needs? It’s no good being armed with the latest and greatest source of carbs if you’ve only got half the total amount you’ll actually need to maintain your performance during a race.
We wrote a guide to figuring out how much carbohydrate you need per hour and that’s a great place to start if you’re looking to optimise your nutrition strategy.
2. What’s the best format of fuel for the scenario you’ll be using it in?
There are numerous options to consider when it comes to fueling exercise. You can choose from drinks, gels, bars, chews and of course, ‘real’ food.
The nature of the event you’re doing, the intensity you’re maintaining and the conditions it takes place in are just a few of the factors that may dictate whether one format of energy is more applicable than the others.
Suffice to say that there’s often a compromise that needs to be made between what is theoretically optimal and what works in practice.
Despite all of this, most nutrition brands still talk primarily about the type of carbs in their products, or other ‘special’ features rather than these more fundamental questions. This is largely because differences in formulation offer a way to differentiate products that are essentially all pretty darn similar in reality.
Brands often offer very little guidance on how much you need beyond generic usage advice like “Take up to three sachets per hour during exercise, less if you're also using a sports drink”!
And there’s little discussion of whether the product format (say a gel, for example) is workable in the scenario you’re planning to use it in (such as a canoe race, where your hands aren’t free to open it!).
To be clear; we’re not suggesting that the type of carbohydrate shouldn’t ever be a consideration when you’re planning how to fuel your activities.
It’s true that different carbohydrates can be absorbed and metabolised at different rates in the body, depending on certain characteristics. And it’s logical to suggest that these characteristics can be used advantageously in some situations - and that certain carb types can even be suboptimal in some scenarios.
But what we are saying is that thinking about the type of carbs in your fuel usually only really makes sense if you’ve already nailed down how much you need to take in and what formats of fuel will work best, if you’re to perform at your best in different circumstances.
Think of it this way, the technology in the Nike Air Zoom Alphafly NEXT% road shoes is very impressive. But if you get them in a size 6 when you’re actually a size 9, the technological benefits don’t get to show themselves. That’s a good analogy for simply taking in the wrong amount of a fancy new type of carbohydrate fuel.
Similarly, let’s say you do get your shoes in the right size, but you try to run a wet trail race in them, you’re unlikely to be standing on the podium at the end because they’re designed for running on the road, not the mud. Again, this would be similar to using a solid energy bar during a marathon when you’d actually be better off with a carb drink or gel.
In most cases, once you’re confident that you’ve nailed down how much carbohydrate you need to take in to maintain your performance and what sources of fuel work best for your needs, you're already getting things 95% right, so the margin for further improvement is slight. It’s only really worth getting into the ‘marginal gains’ once you’ve ticked off the basics.
So, if you feel like that’s where you’re at now, or if you are just curious about the differences between types of carbs you might find in your sports nutrition products, we’ve broken some of this down here.
The different carbs you see on sports nutrition packaging
Carbohydrates can be split broadly into three groups: sugars, starches and fibre.
Sugars are simple, single or short-chained carbohydrates, whereas starches and fibre are longer, more complex molecules. When you ingest sugars and starches (but not fibre), you’re providing your body with energy.
Though there are a handful of exceptions (including syrups like golden or agave), as a general rule for identifying sugars on labels, look for words ending in ‘ose’. The monosaccharides glucose and fructose (the sugar in fruit) are good examples of this.
All carbohydrates, no matter how big and complex, must be broken down by enzymes in your gastrointestinal (GI) system into these single sugars in order to be absorbed into your bloodstream.
How simple sugars are absorbed into your blood
Despite both being single units, glucose and fructose don’t undergo the same absorption process to enter the bloodstream and, in fact, fructose is absorbed significantly more slowly than glucose.
Glucose is transported by the sodium-glucose cotransporter protein, SGLT1, which becomes saturated by the sugar at a rate of around 1 gram per minute (i.e. approximately 60 grams per hour, g/h). At higher ingestion rates, a bottleneck starts to occur where there may be more glucose waiting in the gut, but it’s not going anywhere until there’s an available protein to help it cross the gut wall into the bloodstream.
This sounds like a flawed system but, as things go, glucose is a rapidly absorbed carbohydrate and with intakes of up to ~60 grams per hour (which is an appropriate hourly carb intake for many endurance athletes), it’s a simple and easily accessible choice. Not to mention, once it makes it into the body, glucose can be used directly by the muscles and it doesn’t have to undergo any further conversion steps which slow down energy availability.
As I mentioned, fructose is not as quick as glucose at making it out of the gut. Fructose is absorbed at approximately half the rate (0.5 g/min – approx. 30g/h) and must first be processed by the liver into glucose or lactate before being useful to your muscles.
While fructose might now sound like an inferior choice (and in some ways it is), there’s a benefit to consuming it alongside glucose during intensive, prolonged activity when your carbohydrate needs might be much higher.
Fructose uses an entirely different transporter protein (GLUT5) than glucose to enter the bloodstream, which means that the co-ingestion of glucose and fructose in a 2:1 ratio allows a greater total absorption of carbohydrate (i.e. up to ~90 g/h).
Think of it like you’re in line for the checkout at the grocery store and a second cashier opens up their lane, this speeds up the checkout process and increases the rate at which people are leaving the store.
The pros and cons of glucose and fructose
|+ Rapidly absorbed into your bloodstream (1g/min)||- Very sweet in taste|
|+ Has a high glycaemic index (i.e. it has a rapid effect on your blood glucose levels)|
|+ It’s in the form that your muscles need so there’s no delay in energy availability once the glucose has been absorbed|
|+ Ingestion alongside glucose in a 2:1 ratio raises the total carbohydrate oxidation||- A low glycaemic carbohydrate, so provides the body with energy at a relatively slow rate|
|- Has to be processed by the liver before being used for energy by your muscles|
|- Can cause GI issues (bloating, diarrhoea, gas) if ingested in excess. Although the gut can be trained to ingest more fructose, if slowly introduced|
Disaccharides are sugars made up of two monosaccharides and they also fall under the term ‘simple sugars’. The two main disaccharides you may come across on your sports nutrition product labels are sucrose (simple table sugar) and maltose (often a by-product of starch breakdown).
Complex carbohydrates, also called starches or polysaccharides (poly- meaning many), are longer chained molecules.
Generally speaking, complex carbohydrates are digested more slowly. This is why a bowl of pasta or rice often leaves you feeling fuller for longer than a handful of sweets; the breakdown of the pasta/rice takes longer in your GI system.
There are exceptions to this rule though. There are carbs which fall into the ‘complex’ camp because of their structure, but that are still broken down and utilised for energy rapidly. Enter maltodextrin…
Maltodextrin is a carbohydrate used in many traditional sports drinks. It’s an unbranched molecule 10-20 glucose units in length, made mainly from corn starch.
Despite its longer length, maltodextrin is still easily absorbed, as rapidly as glucose even. This can be attributed to two things...
- Its digestion starts in the mouth with the enzyme found in saliva called amylase.
- It has a low osmolality, which allows it to use less water to be digested than other carbohydrates. It also empties from the gut faster.
This, coupled with the fact that maltodextrin is less sweet than sucrose or glucose (which comes from the Greek word for ‘sweet’, glykós), is why maltodextrin is a very popular carb choice in sports nutrition products.
‘Unique’ carbohydrate types
For the sake of comparison, it’s worth covering the pros and cons of a handful of more ‘unique’ or hyped carb types that you may have heard about, or used.
The arrival of hydrogels a few years ago caused quite a stir in the sports world, especially when ‘hydrogel technology’ was reported to be involved in Eliud Kipchoge’s fueling strategy during his Breaking2 record attempts in 2017 and 2019.
A hydrogel is a ‘gel-like’ solution, usually a maltodextrin and fructose mix, with the addition of sodium alginate and/or pectin. These two ingredients cause the carbohydrate solution to undergo gelation upon contact with the low pH of the stomach (i.e. they form a gel when they hit stomach acid). The proposed advantage of this is that it allows for some of the carbohydrate to escape the stomach undetected, which may speed up gastric emptying.
This is a somewhat surprising claim because there’s well-documented evidence that gastric emptying isn’t usually the rate-limiting step in the absorption of carbohydrates. That’s considered to be intestinal absorption, the next step in the process.
With this in mind, sports scientists from around the world were quick to investigate these claims and, so far, the research (see here and here) hasn’t shown a clear positive effect by hydrogels on performance, total carb oxidation or gastrointestinal comfort. The hydrogels haven’t performed worse than other ‘traditional’ carb solutions in studies, they just haven’t been shown to outperform them either…
It’s still pretty early days and it’s always possible that the ‘right’ studies haven’t been done yet, but at the moment hydrogels don’t necessarily seem to be the White Knight that the marketing campaigns would have you believe they are.
For a more in-depth review of hydrogels and the current status of the research, I’d recommend a listen to researchers Lewis James and Stephen Mears discussing the topic on the Fuel the Pedal podcast.
The pros and cons of hydrogels
|+ They deliver a mix of maltodextrin and fructose, which allows for high carb oxidation rates||- So far, the hype is not backed up by research. (The research so far has only shown ambiguous results when compared with ‘traditional’ sports drink and gel mixes)|
|- They’re expensive|
SuperStarch™ is a trademarked, modified corn starch designed to deliver energy slowly as a result of its gradual breakdown in the intestines. It’s a complex molecule that your body’s enzymes take a relatively long time to chip away at. This slow breakdown is reported to negate the need for an insulin response in the body and help to maintain more stable blood glucose levels (no spike = no crash).
Its original use was in the treatment of a rare genetic disorder called 'glycogen storage disease' where sufferers have to find ways to release energy from food more slowly due to the inability to produce and store glycogen.
The purported benefit for athletes is that without the release of insulin sparked by a big surge in blood sugar levels, your body can proportionally metabolise more fat for energy, preserving your muscle glycogen stores for when you need them.
Utilising our fat stores for energy during prolonged exercise can be beneficial because our fat reserves, within a sporting context, are virtually unlimited (even the leanest of athletes have enough fat to fuel hours and hours of effort!), whereas our carb stores are far more finite, depleting within 90-120 minutes of exhaustive work.
This slow-burning, easily digestible carbohydrate may offer some benefits for those looking to fuel ultra-endurance performances, but less applicable for high intensity, shorter activity, when energy is required more rapidly.
SuperStarch™ does come at a premium price, so if you’re thinking of making it your go-to carbohydrate source, you may need to take that into account and it has also had its claims challenged from a legal standpoint too.
The pros and cons of SuperStarch
|+ It’s a soluble carb with a low osmotic pressure, meaning it passes through the GI system quickly, limiting the risk of GI disturbances||- It’s not suitable for high intensity exercise, when high carbohydrate intakes are required and when carbs need to be rapidly broken down to fuel maximal efforts|
|+ It’s a low glycaemic index carbohydrate that provides a slow release of energy||- It’s expensive|
|+ It enables your body to metabolise fat alongside the SuperStarch. This may be particularly effective for ultra-distance events||- Some report GI issues associated with its use|
Also known as highly branched cyclic dextrin (HBCD), cluster dextrin is a carbohydrate made ‘in vitro’ (within glass) by taking amylopectin (a complex, highly branched carbohydrate 10 to 100 glucose molecules in length) and a ‘branching enzyme’ to break and reattach the glucose molecules in a cyclical structure.
I’ll just let you re-read that last paragraph again as I know it was a mouthful.
Ok, the final output of all those complicated words is a soluble carbohydrate with a low osmotic pressure (meaning it passes through the GI system quickly) containing 60-70 glucose molecules.
A bit like SuperStarch, cluster dextrin provides a steady release of energy. Unlike the bonds in maltodextrin, which all break down at once, the bonds holding cluster dextrin together take more time to ‘unwrap’, and this results in your body being ‘drip fed’ with carbs.
Again, this steadier provision of energy lends itself to prolonged exercise of low to moderate intensity, but less so to higher intensity work, like breakaways and sprint finishes, where success requires the rapid breakdown of carbohydrates.
The use of ‘slower breakdown’ carbohydrates like cluster dextrin and SuperStarch™ mean they ideally need to be used in combination with higher glycaemic carbohydrates like glucose and maltodextrin if high intensity work is necessary - as it is in most competitive sports.
The pros and cons of Cluster Dextrin™
|+ It’s a soluble carb with a low osmotic pressure, limiting the risk of GI disturbances||- It’s less suitable for high intensity exercise, when high carbohydrate intakes are required and carbs need to be rapidly broken down to fuel maximal efforts|
|+ It’s a low glycaemic index carbohydrate, which provides a slow release of energy making it useful for long duration, low-intensity exercise||- It’s expensive|
Multi-Transportable Carbs (2:1 Glucose to Fructose ratio)
In the early 2000s there was a lot of interest in research that suggested athletes could absorb and use more carbohydrate by ingesting a combination of glucose and fructose, when compared to just taking in glucose or glucose polymers alone.
The theory was that whilst glucose uptake rates seemed to hit a limit at around 60g per hour, fructose (which uses a different receptor molecule in the gut) could simultaneously be absorbed at a rate of around 30g per hour leading to the potential of a 90g per hour ‘ceiling’; quite a bit higher than was previously thought.
By 2008, more research showed some impressive performance gains using this method. Since then, 2:1 Glucose-Fructose ratio products have become more widely commercially available and are still routinely used by many athletes today.
Of all of the many and varied ‘claims’ made about certain carbohydrate types and blends, the concept that a ~2:1 Glucose to Fructose mix is useful when you want to ingest really large amounts of carb per hour seems to stand up to scrutiny better than most.
Interestingly, new research and studies of what elite runners and cyclists are doing in the field has started to emerge, suggesting that intakes of over 100g of carbohydrate is possible and is routinely achieved by many pro and elite athletes.
That being said, it still seems that using some combination of glucose and fructose is likely to be beneficial in helping to facilitate this feat, even if an exact 2:1 ratio is not set in stone.
The pros and cons of MTCs / 2:1 Glucose:Fructose ratio
|+ Can allow ~90g of carbohydrate to be absorbed per hour||- Some people respond less well to fructose than others, resulting in greater incidence of GI distress in high fructose products|
|+ Backed by robust lab-based evidence and anecdotal experience with athletes|
Are all carbs created equal?
On the one hand, there definitely are some distinct differences in the ways different carbohydrates are absorbed into your body, the rate they’re absorbed at, the risk of GI distress they pose, and the level of sweetness they come with.
Yet on the other hand, all carbs are somewhat equal.
Regardless of the type you put into your system at the start, whether it be glucose, maltodextrin or a hydrogel, all carbs end up in your bloodstream as glucose to be used by your muscles.
Each type of carb has its own pros and cons that can be worth considering for marginal gains, but only if you’ve already answered the more important questions of how much carbohydrate you need to be taking in per hour, and what fueling formats are likely to work best for you in the circumstances in which you’re planning to use them.
If you’re in the market for taking in really high amounts of carbohydrate per hour (i.e. well in excess of 60g per hour) which seems to be important for very high intensity long duration efforts, then using a ~2:1 glucose to fructose ratio might be worth considering as it does have some solid science behind its effectiveness.
However, the focus should be on nailing your carbs per hour numbers and fueling formats as a priority before getting too caught up on the finer detail of the type of carbohydrates you're consuming.
Ultimately, it’s nailing the basics that will give you the lion’s share of potential gains.
- How much carbohydrate do athletes need per hour?
- How to choose the right energy product formats or foods to fuel your performance
- Should you use carbs or fat to fuel endurance exercise?
- How to get your nutrition strategy right for endurance performance
- What happens when you ‘bonk’? (And how to avoid it!)