Thanks for the resources.
Now wondering if/how a GLU+FRUC mixture differs from a straight SUC solution?
There is no need to break the G-F mixture (as there is with SUC) for absorption, so what effect does this have on the body (e.g. hormone release, etc.)?
Sucrose works virtually identically to glucose plus fructose.
100-150g/L usually works out well.
Energy density matters more than osmolarity (molecule number) by a wide margin. So much so that some of my peers pay absolutely no attention to osmolarity anymore.
Alex,
what are your thoughts/tips on using a concentrated bottle for nutrition?
For the bike leg of my last IM I mixed 280g of maltodextrin in an 800mL bottle, which would last for 4h (so 70g of carbs per hour). After every sip of the concentrate, I would take an equal sip of water in order to avoid any stomach issues. While it did seem to work, I am interested in improving the mix by adding fructose.
Thanks for your contributions, it has been interesting reading.
That’s precisely what my wife and I do. Usually 250-500g carbs in a 1 L bottle. Swig the carbs, then chase with water.
Read more throughout this thread here Help me calculate an at home "maurten" drink (im bad at math) (Page 5): Triathlon Forum: Slowtwitch Forums
Look for the pics of my wife’s bottle prep for her single-day Festive500.
I am getting so confused between the types of sugar.
So feasibly you could just mix 100g table sugar (sucrose?) with water and you’d have a even split (50-50) between glucose and fructose?
But in your slowtwitch posts, you suggest mixing Gatorade with table sugar, is that to make it more palatable as 100g of table sugar would be too sweet? What type of sugar is in Gatorade? Isn’t it a mix of glucose and fructose already? 
Thanks for posting btw, it’s useful to be able to clarify.
This bit still hurts my head a little. I always wondered how fuelling anything under an hour could help as I always hear people saying you need to fuel 3 or so hours before a ride. So how does fuelling while on a 60 minute trainer session help? 
The 3 hours in advance thing is when you have a complete meal as part of normal nutrition. You might eat more carbs than normal in preparation of an intense workout and what this does is fill up your glycogen storage, I believe this is in the liver and in the muscles.
During the workout it only makes sense to ingest quick carbs that are much faster absorbed. So sugar in water just takes minutes. For workouts shorter than 1 hour it is not an absolute necessity to eat, because you should have enough energy stored.
But, ingesting quick carbs during the workout, also shorter ones, for me makes the workout easier and that is also what others have experienced. I can imagine a few reasons why:
Our bodies are not digital on/off machines and there are mechanisms in place to protect you from dying if you forget to eat. So your glycogen storage is not like a fuel tank that can be used at full speed until empty, rather your body starts to slow down fuel consumption before it runs out. So by ingesting glucose, you will stay longer out of the almost empty zone where less glycogen is delivered to the muscles.
For fructose I can also imagine that although it takes a long time before it is actually used as glycogen, just absorbing it might already tell your body that glycogen is on the way and it could already release more of the stored glycogen. I know it works like that if you just rinse your mouth with something sweet.
Nice reply, many thanks!
Maybe it is a coincidence, but if you dissolve carbs in water, then having the same energy density also means roughly the same osmolarity once all the molecules are split into glucose and fructose.
Yup! Correct.
I like the taste. 
It’s still similarly sweet, but with a lower flavor intensity than if you were to do 100% Gatorade powder to get to the 100g, and with more optimal sugar ratios and cheaper cost.
Gatorade is sugar, then dextrose, per their ingredients list. Companies won’t give away their industry secrets like sugar ratios. I’ve asked! If they’re smart, it’s almost entirely sugar. If not, it’s probably close to 1:1 sucrose to dextrose, which yields 2:1 gluc:fruc ratio. I’m guessing it’s that, because Gatorade is a huge 2:1 proponent.
FYI: dextrose = glucose. Dextrose = outside the body. Glucose = inside the body. Silly nomenclature, alas.
@mrpedro nailed it. Intra-workout carbs increase cognitive drive and keep blood sugar elevated (ideal!) during training. Pre-training meals 2-3 hrs before, stock a bit of glycogen and pre-boost blood sugar for training start.
Osmolarity of glucose + fructose is almost double the osmolarity of sucrose for an isoenergetic solution, I believe, but have not checked the math. Maltodextrin + fructose almost matches sucrose for osmolarity of an isoenergetic solution.
I don’t believe that sucrose is hydrolyzed (split) into gluc + fruc when dissolved in water. Only once an enzymatic breakdown occurs would osmolarity increase, and I need to brush up on precisely where and in what parts of the GI tract that occurs, and at what rates, and by what mechanisms
I tend to stay quite “applied” in my research and once I find the answer like “sucrose works as well as malto+fruc” I tend not to dive too deep mechanistically. Too many rabbit holes and too great of time-cost. And many of the greatest misconceptions in sport science have come from mechanistic understandings without actual testing in vivo! (see 30/60/90g/hr fruc/gluc/sugar dogma! lol)
Yea, in water it doesn’t split. But it looks like all the sugars are split into glucose and fructose before it goes through the intestinal lining. See for example: What Is the Difference Between Sucrose, Glucose & Fructose?
I can see the bit where you just want to focus on results. There are too many correlation-not-causation things going on, where we don’t fully understand the underlying mechanisms and are too quick coming to conclusions.
For me, I must say that the 2 times I did use sugar during a workout it really made the long intervals around threshold much easier.
Firstly thank you Alex for the info and awesome explanations.
I think I get it that normal table salt (sucrose) can be used with water to provide the 1:1 ratio of glucose and fructose.
Table salt isn’t great for sodium needs because of the possible GI distress you mention. But sodium citrate gets around this having more sodium bang per molecule!
So in summary, if aiming for 90g of carbs an hour in your mix it’s as simple as 90g or table sugar plus a teaspoon of sodium citrate and you’re good to go?
Just thought it would be worth spelling out really explicitly for the slow people like me!
Yep! I flavor by using 10-30% Gatorade, and remainder table sugar for the carbs. FYI half cup sugar ≅ 100g.
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It completely changed my attitude to fueling on the bike and eliminated any gut issues from carb intake in fluids/gels. For most of my rides <2Hrs I don’t take in any carbs, but I do have some before the ride. Intense rides (intervals) I’ll have at most 40g in a 1L hydration drink and I normally have 2x 1L bottles on the bike. Longer rides I normally take a couple of rice cakes and eat them around the 1Hr and 2.5-3Hr mark. I’m not doing any rides over ~4Hrs at the moment. I’ll have to re-evaluate when I do.
So in an attempt to get to 100g + carbs I bought a load of fructose from Amazon. In the ingredients it’s actually fructose + sulphur dioxide.
Anybody know if that’s fine to have in my sports drink? Google isn’t really helping.
So this is interesting. I think it might be where I am going wrong.
I took this advice (wiggle mix not gatorade). I was pleased that it was actually pretty palatable. I’ve stared with 60g carbs, but plan to build up to a higher hourly amount.
But I attempted it during a sweet spot workout with long intervals. It was fine at first, but then it was definitely not fine. I had to stop fuelling to be able to finish the workout. I’ve had the same reaction with 60g of carbs but with different sugar ratios.
Admittedly, it does seem to be common sense to try these things out with lower intensity first, but it seems to me way more important to fuel harder workouts.
So maybe it would be better to try and fuel more before hard workouts and take on a lower concentration carb drink during the workout. Separately train up my gut during low intensity long rides to be able to take on 100g per hour.
Am I missing something really obvious because I am one of…
What volume of fluid and sodium are you using with your 60g/hr roughly?
750ml fluid, so 8%(?) concentration, and tsp of sodium citrate…
I’d consider slightly reducing sodium citrate maybe (for reduced osmolarity) and maybe even reducing fluid volume, if that 750mL is an hourly rate, unless you’re experiencing thirst. Tough call. You’re in the “it’s good enough that it’s going to be trial and error at this point” range.