I'm finally sitting down to start writing this up. In the last post, I laid out my recent discovery of just how important it is to properly fuel the body for endurance events - something that if I had done up to this point, it was more by accident than by design.
Generally, my primary fuel during long bike rides or runs has been Gatorade. At 50 calories per 8 oz serving (about 14g of carbs), one would need to consume about 20 oz per hour to reach the 'suggested' 35g/hr of carbs as referenced on this page @ www.runningforfitness.org. Keep in mind that the 35 g/hr is on the low side - elsewhere on that page it also mentions that the average person can take up 30-60 g/hr. Also, keep that 60 g/hr figure in mind - it'll come up again later. While 20 oz per hour of Gatorade is certainly achievable (especially since many rules of thumb mention 24 oz of sports drink/hr) - in my case I tend to mix the gatorade a little light, and to be perfectly honest, I'm not always so good about keeping to that regiment. Other factors, such as not wanting to deal with a stomach full of liquid, or availability of water, come into play all to often - especially on bike rides. Thus, it may be more convenient to find additional energy sources.
Usually people migrate to some sort of energy gel for this purpose. There are a bunch of them out there, but just taking a quick look at some examples of the common ones I've come across:
Chocolate Outrage Gu:
100 calories (20g carbs)
70-80% maltodextrin
30-20% fructose
Hammer Nutrition Gel:
This one isn't so straight forward (if you check the link, there is all kinds of scientific techno-babble). But for the purpose of this post, the linked page indicates that they use a ratio of about 7% simple sugars and 93% long-chain carbohydrates. Later on they say that sucrose (table sugar - which is 50% glucose and 50% fructose) and fructose are considered simple sugars, and that maltodextrin is a multiple of sugars hooked together. The wiki page on maltodextrin corroborates this. So, for simplicity sake, we'll say the following:
90 calories (21g of carbs)
93% maltodextrin
7% fructose
Powerbar Energy Gel:
Powerbar uses their C2MAX carb mix, which they claim is a 2:1 mixture of glucose to fructose.
110 calories (27g carbs)
66% glucose
33% fructose
So at this point, two things are obvious - each manufacturer has a different idea of what is optimal, and that they all use a combination of simple sugars and more complex sugars. It may also be worth keeping in mind that perhaps each manufacturer has a different idea of the market they want to play in - for example, one may want to promote their product in shorter races (10k or whatever) and want a faster absorbing fuel. Another manufacturer may want to be strong in longer events, such as a marathon or anything beyond a sprint triathlon, and may want a fuel that isn't as 'spikey' on its energy surge.
Since I didn't know what the target market was for each, the next thing I could look at was the differences in the various fuels. For that I turned to my trusty friend, Wikipedia. I decided that for this it'd be a trustworthy source - how sugars are digested is common enough knowledge in biology circles that I'd seriously doubt there would be any major misstatements.
In looking at the entry for glucose, the following stick out:
- Primary fuel for all cells in the body
- Simple sugar (monosaccharide)
- Dextrose is another name for it
- The base carbohydrate that other carbohydrates get broken down into
- Transported via the SLC5A1 protein
- Directly transported to muscle cells, where it can be converted to glycogen for short term storage
In looking at the entry for fructose:
- Simple sugar (monosaccharide)
- Mentions that it and glucose can be absorbed directly into the bloodstream
- Metabolised in the liver, whereas glucose can pass through the liver and be metabolised directly by cells in the body
- Absorption rates vary, but some studies indicate absorption is highest when fructose and glucose are in a 1:1 ratio (ie, table sugar) due to a bottleneck in the GLUT5 transport protein, which is required for absorption of fructose.
Maltodextrin:
- Essentially X glucose molecules strung together, where X is between 2 and 20
Unfortunately there's not a lot of other information on Maltodextrin, but from what I can gather, since it is simply glucose molecules all tangled up, it almost acts like a time-release capsule of glucose.
The reason why I bothered to point out the transport proteins is to point out that different sugars apparently have different ways of getting absorbed through the intestine, so it stands to reason that it is possible to saturate one transport mechanism, while the other is idle. In other words, if all you fueled yourself with was glucose, you may saturate your body's ability to process it because there is only so much SLC5A1 protein to go around. Meanwhile, GLUT2 proteins are floating around with their figurative thumbs up their asses.
When you look at Powerbar's information on C2MAX, they claim that part of the reason why they feel their product is superior is that their researchers discovered that the previously understood limit of absorbing 1 g/min of carbohydrates (remember that 60 g/hr figure?) was only for glucose. Just because glucose has a maximum absorption rate of 60 g/hr doesn't mean significant additional absorption cannot be happening in parallel with fructose. Yes, fructose may have to detour through the liver first, but when you are talking a multi hour endurance event - there is plenty of time available for fructose to become effective. Honestly, whether you want to believe the whole idea that a specific ratio of glucose/fructose provides the 50% additional uptake in carbs that they claim or not is up to you. But it is interesting nonetheless, especially when you consider the various products, the types of carbohydrates they choose to use, and the question of what their target market is.
In the next post - homemade energy gel.
No comments:
Post a Comment