As a coach I get asked about nutrition regularly and as an athlete I have had my fair share of race disappointments bought on by sub-optimal fuelling on race day. There seem to be many myths and obviously some great marketing around race week and race day fuelling and with the sizeable investments (time and money) that go into getting ready for 70.3 and Ironman racing- being correctly informed is worth the effort.

Don’t leave your race day nutrition at the whim of marketing. Do your research and then practice, practice, practice your race fueling strategy. Every long session provides the opportunity to refine your fueling for race day.

More and more products are popping up with what is known as a 2:1 ratio of maltodextrin to fructose, with claims of better carbohydrate delivery which leads you to being able to ‘consume’ more and thus lead to better performances. Is this just pure marketing hype or do the stated scientific studies measure up?

I went to Steve Born of Hammer Nutrition to get his take on the studies as Hammer’s line in the sand for endurance fuelling is “Stick with complex carbohydrate fuels, don’t consume simple sugars with or within close proximity of complex carbohydrates, and we guarantee you’ll see better results.”

Now before I go any further, you may be sceptical and think that Steve, being from Hammer is biased in his information and only wants to sell you on the Hammer line of products. There is nothing wrong with wanting to sell products as that is a reason for being in business but it’s the value the company gives to its customers that is important. Hammer provides tons of value.

In the words of Timothy Ferris “Be proactively sceptical, not defensively sceptical”. Find me another endurance sports nutrition company with the amount of thoroughly researched and available education than Hammer has on its site. I highly recommend you go and spend some time well spent at Hammers Knowledge base section – you won’t regret it.

Here is Steve’s take on the studies that many companies are now citing as their reasoning for the 2:1 Maltodextrin/Fructose they use in both their fuels and marketing.

Hello Kristian –

It’s very nice to hear from you, and thanks for emailing me. As I’m sure you’re already aware, the “multiple carbohydrates are better than a single carbohydrate source, including maltodextrin” studies aren’t really all that new. And though the studies were done by a highly respected sports nutritionist, Dr. Asker Jeukendrup, and while the way the studies were conducted were absolutely pristine, if you look closely at the studies you’ll see a fairly significant reason why we don’t believe their results have applications in “real world” training and racing (i.e. things can oftentimes be significantly different in a lab than they are when you’re out there riding your bike in ‘real world’ conditions).

We discuss this in the article “Caloric Intake – Proper amounts during endurance exercise,” in particular the section entitled “Complex carbohydrates only or a combination of carbohydrate sources: Which is better for the endurance athlete?” That chapter is part of the updated booklet,The Endurance Athlete’s GUIDE to SUCCESS (click to download), and I’ve taken the liberty of cutting and pasting that particular section for you here:

Findings from research conducted by the Dutch sport scientist Asker Jeukendrup has caused quite a stir. In fact, a few companies produce fuels that contain the carbohydrate formulations used in the studies. In general, Jeukendrup found that a blend of carbohydrates increased oxidation rates, indicating higher energy production. In one study, cyclists who ingested a 2:1 mixture of maltodextrin to fructose oxidized carbohydrate up to 1.5 grams/minute. Another study used a mixture of glucose, fructose, and sucrose and had rates that peaked at 1.7 g/min. Both those results are pretty eye opening, considering that complex carbohydrates typically oxidize at a rate of about 1.0 g/min.

However, there’s more to the results than what first meets the eye. Most of Jeukendrup’s subjects cycled at low intensity, only 50-55% maximum power output, which I think we’d all agree is very much a recovery pace, if that.

To be blunt, at a leisurely 50% VO2 Max pace, athletes can digest cheeseburgers and pizza with no gastric issues. However, if the heart rate and core temperature are raised to only 70% VO2 Max, the body must divert core accumulated heat from central to peripheral. This reduces the blood volume available to absorb ingested carbohydrates or whatever the athlete has consumed. After over two decades of experience, we have found that in the overwhelming majority of the athletes we’ve worked with, athletes engaged in typical 75-85% efforts and/or in multi-hour endurance events, the combination of simple sugars and long chain carbohydrates, and in amounts higher than approximately 1.0-1.1 grams per minute (roughly 4.0-4.6 calories per minute), have not yielded positive results. They did, however, increase performance-inhibiting, stomach-related maladies.

Dr. Bill Misner writes, “Absorption rate and how fast the liver can ‘kick it out’ are limiting factors. No matter what you eat, how much or how little, the body provides glucose to the bloodstream at a rate of about one gram/minute. Putting more calories in than can generate energy taxes gastric venues, electrolyte stores, and fluid levels.”

Lowell Greib, MSc ND, explains that gastric emptying is a key limiting step in carbohydrate metabolism: “If your stomach can’t empty the product (no matter what it is) you are going to get nothing from it except a huge gut ache and possibly lots of vomiting! Unless there is new research that I am unaware of, gastric emptying is directly proportional to the osmolality of the solution in the stomach. Long chain carbohydrate (maltodextrin) contributes less to increasing the osmolality than do disaccharides (sucrose, lactose, maltose, etc.).”

The question is not whether or not Jeukendrup’s published studies are disputable, but rather if these studies apply to faster paced, longer duration bouts of exercise. We do not believe this to be the case, which is why we do not recommend the use of multiple carbohydrate sources during exercise.

Bottom line: Stick with complex carbohydrate fuels, don’t consume simple sugars with or within close proximity of complex carbohydrates, and we guarantee you’ll see better results.

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Another article that I wrote, “Simple Sugars and Complex Carbohydrates – An Incompatible Combination,” also discusses this issue. You’ll find that article here.

So again, the results of the studies are not disputable. However, given that the subjects in the studies (and there weren’t many) were exercising at a very low exertion level – basically a recovery speed, if that – it doesn’t really apply to even moderately paced workouts and certainly not races, when exertion levels are much higher. As I stated in the “Simple Sugars and Complex Carbohydrates” article” –

The beauty of complex carbs is that they will match body fluid osmolality, not at a 6-8% solution, but a more concentrated 15-18% solution. Even at this seemingly too-high concentration complex carbohydrates (such as maltodextrins/glucose polymers) will empty the stomach at the same efficient rate as normal body fluids and provide substantially more calories (up to three times more) than simple sugar mixtures will. However, when simple sugars and complex carbs are consumed together or near each other, it increases the solution concentration beyond what either source can be efficiently digested at. In other words, when you consume simple sugars and complex carbohydrates together or within close proximity of each other you negate the efficient digestibility of either source.

1) If the athlete consumes a simple sugar fuel the body will only permit 6-8% of it in solution into circulating serum for fuel replacement.

2) Complex carbohydrate fuels are easily and more-rapidly absorbed in a 15-18% solution. More calories are absorbed faster, and are available for energy production, from complex carbohydrates than simple sugar.

The higher the simple sugar content, the higher the solution osmolality, the less of it is absorbed immediately. The longer the chain of sugars linked together as a complex carbohydrate the more of it is absorbed in higher solution because its osmolality is closer to that of body fluids.

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So what it comes down to is the osmolality of the carbohydrate source and how it matches (or doesn’t match) body fluid osmolality parameters. Now, if you’re going to be working out at only 50-55% of max (which is what the test subjects did) then yes, you can digest just about anything. Exercise at an intensity higher than that and it’s almost guaranteed that you’re going to have stomach issues (or worse). That’s why we don’t recommend combining simple sugars with complex carbohydrates… we really believe it’s a recipe for disaster.

Lastly, here is some research that shows the superiority of complex carbohydrates:

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Thanks Steve for the indepth answer.

One thing that I believe is important to note. When finding your own perfect race fueling strategy for you. The basis should be finding the minimum effective dose. What is the MED that will give you the most performance benefits without the stomach problems. That IS and should be the goal. More doesn’t = better.