I have been reading a lot on the forum about drinking carbs on the bike. and have a few questions:
Is there any benefit from drinking fructose for rides under 1.5 hour, if it takes that long for consumed fructose to be available for energy? Perhaps it still helps with reducing RPE as our body detects that more carbs are on the way?
If we stick to the 60g of glucose can we use any mix of Maltodextrine / simple Glucose as long as there is enough water to absorb? So e.g. in a bottle of 750ml, we could add anything between only 60g of Maltodextrine, down to 30g Maltodextrine with 30g of simple Glucose and still have some space for a pinch of salt and citric acid for taste. Would it matter at all for performance? I guess one reason to go more towards Maltodextrine is if it is cold and we don’t expect to drink 750ml in an hour?
I don’t really get the Isotonic thing, on one way we are saying that the carbs only get absorbed once the concentration is similar to the concentration of dissolved particles in our body, but if that is the case then why is it dangerous to drink seawater as it increases the concentration of salt in our blood and extracts water from cells? If the salty water gets absorbed with high concentrations of salt, why doesn’t the water also get absorbed with high concentrations of carbs?
Salty water in your stomach/intestines will initially draw more water from your body, dehydrating you. You may end up with diarrhea, thus losing more water. And the salt that does get absorbed, your kidneys end up excreting a ton of water to get rid of the salt.
High concentrations of carbs will similarly draw body fluid into the digestive system, but as it gets actively absorbed and metabolized you don’t have excretion problems.
Yes. Absolutely. For more info check out these related threads over on slowtwitch.
The TLDR of all my comments over there is:
- Performance enhancement happens for anything over 60min. Probably useful to fuel appropriately for shorter rides than that.
- Use closer to a 1:1 Glu:Fru ratio. 2:1 Glu:Fru ratio is old dogma.
- Sucrose works as well as maltodextrin+fructose, and probably better than glucose+fructose.
- 90g carbs per hour is bogus dogma. 120-150g/hr is no problem.
- 10-18% beverage concentrations are often well-tolerated. (100-180g sugar per liter).
- Hydration must be maintained. Use a minimum of 500-1500mg sodium per L. Maybe more…
Bingo! Multiple transportable sugars is key. Newer research pretty clearly indicates we can go a lot higher than the old dogma of 60/30/90 (60 glucose, 30 fructose, 90 total). Please let those numbers die!
Here’s 3 awesome sources that say so. (PDFs attached, I think… I’m new to this specific forum)
I routinely do ~75g glucose, 60g fructose, and ~135g total carbs per hour on rides lasting 2-5 hrs.
Use sucrose and Gatorade. More info here: Saving Money as an Endurance Athlete
TROMMELEN_2017 Fructose and sucrose intake increase exogenous carbohydrate oxidation during exercise.pdf (1.8 MB) GONZALEZ_2017_Glucose plus fructose ingestion for post-exercise recovery-Greater than the sum of its parts.pdf (1016.7 KB) REVIEW, Rowlands2015_Article_FructoseGlucoseCompositeCarboh.pdf (785.1 KB)
Good news! It does work like that! And y’all literally can just dump sugar in a bottle. Save yourself some money. Not kidding.
With utmost respect for Dr. Asker Jeukendrup who is a legend and pioneer in the field of intra-workout fueling strategy, that article, and some of the recommendations that stem from his earlier work that continue to make their way into position stands of the ISSN are probably leaving vast swaths of cyclists and triathletes:
With an overemphasis on complexity of beverage (malto plus fruc plus sucrose plus gluc confusion)
Overconsuming glucose slightly, and vastly underconsuming fructose.
This is how I do it: (I’m cheap)
Saving Money as an Endurance Athlete
More info on how to make it work better:
When and How to Use High-Carb Fueling
Thanks for the links.
So for workouts < 1hr, the carbs are not adding much to fuel, because we should have enough stored. But it could help with lowering RPE. So fructose could still help for shorter workouts even if the energy from it only comes after an hour.
I also like to add some citric acid for flavor, cancels out a bit of the sweetness.
Regarding how maltodextrin gets processed in the stomach, first it is cut into glucose before it ultimately gets absorbed. Does that mean you still need to take as much water per gram of maltodextrin as you do for glucose?
Water needs are actually more predicated on energy density of the consumption, rather than osmolarity, FYI. Osmolarity is reduced by using maltodextrin. Energy density is not.
In general, water needs will be similar, regardless of malto vs. gluc use. Maybe 10% less water could be safely trialed while using malto instead of gluc.
But better yet, use sucrose to get your fructose + glucose. When targeting near 1:1 ratio of gluc:fruc (which I assure you is better than 2:1), sucrose alone is a lower osmolarity than malto+fruc.
Is there science to show this?
Question isn’t a condemnation, I’m genuinely interested as I consume ‘sugar water’ on the bike.
Absolutely. Happy to clarify.
100g sucrose = 292 mOsmol/L
50g fructose = 277.5 mOsmol/L
50g maltodextrin with average strand length of 10 (1801g/mol) = 36mOsmol/L
36 (malto) + 277 (fruc) = 313.5 mOsmol/L
From the Gonzalez paper (GONZALEZ_2017_Glucose plus fructose ingestion for post-exercise recovery-Greater than the sum of its parts.pdf (1016.7 KB)
Also this paper shows super high exogenous oxidation rates using 1:1 ratio.
JENTJENS & JEUKENDRUP 2005 ‘1-1 ratio is good!’ high-rates-of-exogenous-carbohydrate-oxidation-from-a-mixture-of-glucose-and-fructose-ingested-during-prolonged-cycling-exercise.pdf (194.5 KB)
There is no need to keep concentration as low as the oft-cited 6-8%, or even 10-12%.
With some practice lots of folks tend to handle 12-18% just fine, especially in colder weather where hydration is less likely to become compromised.
120g/hr could be consumed with 750mL + 1000mg sodium via Sodium Citrate and you’re good to go.
FYI: Sodium Citrate has about 1000mg sodium per tsp. Table salt is about 2000mg sodium per tsp.
Is citric acid the same thing as sodium citrate? I can buy citric acid at my local supermarket.
No, unfortunately. Sodium citrate replaces three hydrogens on the three hydroxyl groups of citric acid with sodium molecules. Once dissolved sodium citrate turns into 3 x Na+ and 1x citrate ion.
Once dissolved citric acid only has hydrogen ions to donate. Okay for sweetness-reduction. Useless for meeting sodium needs though!
Using sodium citrate in place of table salt allows your gut to tolerate more sodium consumption during training. Sodium citrate has 3 sodium molecules for every 1 citrate molecule. Sodium chloride has 1 sodium molecule for every 1 chloride molecule. That means that for the same amount of sodium consumption, there will be a greater number of molecules ingested, if using table salt, rather than sodium citrate. Osmolarity is the number of molecules per unit volume of solution. Our gastrointestinal tracts are sensitive to very high osmolarity solutions. During normal daily living, consumption of very high osmolar solutions (lots of molecules per liter) causes a laxative effect 20-60 minutes after consumption. During exercise, it causes gut cramping, THEN a laxative effect. My personal experience with this can be described as “not fun!”
Bummer, thanks for the great response though.
I mix 1/2 cup maltodextrin, 60 grams of carbs, with 2 TBSPS of fructose, 33 grams of carbs, and a lemon lime flavor packet in 24 ounces of water. That’s around 375 calories. A gram of Maltodextrin or fructose yields about a gram of carbs. It would be easy to increase that to exceed 100 grams of carbs. I wouldn’t want to do a 1 to 1 ratio of glucose to fructose because it would be too sweet tasting.
I do several long slow rides/week, 3+ hours at around 75% of my FTP which burns around 1,300 or more calories. I drink a few swallows from the bottle every 30 minutes or so throughout the ride. At the ½ way point I stop at a c-store and have a Starbucks vanilla double shot, 210 calories, and a Natures Bakery fig bar, 200 calories. That comes to about 785 calories total for the ride. When I finish I have 16 ounces of chocolate milk for a recovery drink, about 360 calories. I typically have a serving of cereal with milk and blueberries and 3 eggs for breakfast before the ride.
If I’m going to ride longer and/or harder I’ll take two bottles. In the summer I fill a camelback with just water and add a little bit of sodium citrate to the bottle. I live in north central Texas and it gets very hot here in the summer. Lots of sweat!
I am taking in fewer carbs during the ride than I’m burning but not by much.
Describing this is making me hungry!
Is it energy density that matters or the ultimate number of particles that the carbohydrates are broken down before absorbed in the bloodstream? I guess it doesn’t matter if only adding carbohydrates to water. So how much water do we need then, it looks like 50g of fructose per liter gives about the right osmolarity, does that mean we should aim for 1L of water per 50g of carbs, regardless of where they came from?
Although I just did 1 bottle of 800ml with 120g sucrose and 60g of maltodextrin plus 1 bottle of only water, for a 2 hour workout. That felt quite good.
Will try a higher concentration of fructose next.
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.
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.