Specific Carb Sources Found in Gels (Glucose & Fructose)
If you’re using a natural carb sources for running like honey, maple syrup, or date syrup then this post is for you.
Running gels are made up of glucose and fructose. The reason is that we have two different transporters that allow absorption of carbs.
The first one utilizes glucose, known as SGLT1, but research found that it generally gets saturated around 60g per hour, so absorbing additional glucose becomes difficult.
This is where fructose comes in. Fructose uses a different transporter, GLUT5.
Glucose is generally the more efficient carb source because it’s readily absorbed through SGLT1, and glucose also appears to enhance fructose absorption.
The Right Amount of Carbs Per Hour
Originally, scientists found that once you approach 60gr an hour of glucose, adding in fructose is a way to get more carbs per hour, and found a 2:1 ratio was beneficial.
This is where the recommendations of 60-90gr of carbs per hour come from. The research and real world data experience show that carbs improve performance.
The thinking is that our transporters get saturated at some point (around 60gr/hr) and so it doesn’t make sense to take in much higher amounts as that can lead to GI distress.
However, more recent research ad well as elite athletes and coaches like David Roach have seen evidence that a higher carb intake around 120gr/hr may improve performance and fatigue resistance more for elite athletes or individuals pushing their intensity limit in longer distance events.
If targeting 90+ Gr/hr, a 1:0.8 glucose to fructose ratio has been proven to be more beneficial as it helps with carb oxidation a more even distribution of carbs sources to prevent one of your transporters from getting over saturated.
If you’re going to target 60+ gr/hr you will likely need to train your gut to tolerate the higher amount of carbs (more on this later)
How Natural Carb Sources Stack Up
Based on this information, if you’re using natural sources of carbs, there are some things to consider.
Honey is approximately 0.75:1 in glucose to fructose ratio, but that can depend on the flowers the bees visited, it can fluctuate in its ratio. That variance makes it difficult to know the exact ratio you’re getting, which can make honey a less predictable source of carbohydrate if you’re trying to precisely control your glucose-to-fructose intake.
Maple syrup is close to a 1:1 ratio, so you could potentially get by with 60g per hour, and maple syrup tends to be easier on the stomach for some athletes.
Dates can also be around a 1:1 ratio, but one thing to be careful with here is fiber.
Some date gels I’ve seen have fiber, and if you’re running for multiple hours, this can slow digestion and potentially affect carbohydrate absorption or cause GI issues after an extended period of time.
So check the ingredients if you plan to use a date source.
The Downside of Natural Carb Sources
Due to the higher glucose to fructose ratio in these natural carb sources it makes them less ideal. Remember that glucose is generally the more efficient carb source so unless your aiming for the higher end of gr/hr (90+) then sticking to gels or a higher glucose source is generally better.
Another consideration is that the sugar found in maple syrup and date syrup is made up of sucrose which is a 1:1 ratio of glucose to fructose. Your body has to break sucrose down into glucose and fructose before it can absorb it. This is done extremely fast in the body but it is another process that has to take place as compared to gels that contain glucose and fructose as already separate sources.
Ranking Natural Carb Sources
So if I had to rank these for endurance running based on glucose-to-fructose ratio and potential GI distress, I would go:
Maple syrup
Date syrup
Honey.
Conclusion
Again, these are viable sources if you’re aiming for 60g/hr or less.
If you want precise ratios and higher carb intake, I would use standard gels. And if you go for 90+ I would use gels with a 1:0.8 glucose to fructose ratio.
If you found this helpful, let me know in the comments and share it with your running friends
Coach Cam.
