how different the body metabolizes each of these two kind of sugars ?
I have been told that fructose cannot be stored in muscle like how glycogen can be. If so, trying to get a high percentage of daily energy from fruits (what Gordo recommended in his article) sounds like a poor nutritional strategy.
I’m not 100% sure, but here is a guess:
Foods with a lower GI take longer to get through your system and provide sustained engery for a longer period of time (foods such as complex carbs). High GI foods (i.e. cake) your body burns up super fast, causing a subsequent sugar crash.
Getting all your energy from fruits seems like a bad idea since fruit is high on the GI index; they are a simpler sugar. Getting engery from low GI foods, like most veggies, is probably smarter.
Now, here is the part I am unsure of: perhaps Fructose and Glucose could have some effect on the GI level of a food; i.e. perhaps foods with a lot of fructose are higher on the GI index. Not sure though.
I haven’t read Gordo’s article, but I would agree that getting all your engery from fruits would be bad. But getting a variety of foods, all non-processed whole foods, would be a great way to fuel yourself. And maybe when Gordo says to get a lot of energy from fruits, that is opposed to getting your energy from PowerBars, Gatorade, Snickers, and other trash. If that is the case, I would whole heartedly agree.
I’ve not read the specific Gordo article you mention… although from reading Going Long it did seem to be a bit heavy on the “it’s natural, so its better for you” front.
Lots of work and controversy about Fructose as a fuel at the moment, there’s evidence that if you take Fructose combined with Glucose, you can increase your rate of carbohydrate absorbion. Powerbar (I think) recently reformulated their drink to include fructose. On the other hand, Fructose has a greater tendency to cause GI distress
Here’s an article that’ll tell you most of what you need to know.
http://www.pponline.co.uk/encyc/sports-nutrition-and-carbohydrate-drinks
I thought I’d seen an article showing a link between Fructose and performance (rather than just absorbtion, but can’t seem to find it.)
Not sure about storage, but last year I participated in a lab test designed to measure the benefits of fructose for endurance cyclists. Seemed to show that it can benefit athletes by increasing the energy available to the muscles during extended (3 hours plus) exercise. Apparently the transport mechanism from digestive system to blood system is different from glucose.
how different the body metabolizes each of these two kind of sugars ?
I have been told that fructose cannot be stored in muscle like how glycogen can be. If so, trying to get a high percentage of daily energy from fruits (what Gordo recommended in his article) sounds like a poor nutritional strategy.
Glucose and fructose are both “simple” sugars, or monosaccharides (carbs that are in their simplest form). Glycogen is a huge molecule made up of heaps of glucose molecules in chains with various branches – this is why you’ve been told fructose can’t be stored as glycogen. For all intensive purposes, glycogen is glucose.
Glucose is the only carb that we can directly metabolise in muscle to extract energy from. You can, of course, do so from fructose, but it has to be converted to glucose in the liver, gut cells and/or enter carb breakdown pathways at different places to where glucose would enter. For this reason, fructose in itself, and therefore fructose-containing foods, have a lower GI than glucose (remember that GI is, in simple terms, the speed and or level with which glucose appears in the blood after eating/drinking). This is the reason for the “slow-release” formula claimed by gel manufacturers – the inclusion of fructose.
As far as Gordo goes, athletes often make the mistake of assuming that nutrition is merely carb, fat and protein. Gordo and those like him probably suggest fruit, etc for the general health benefits more than just the carbs, etc, as many foods you would select specifically for carb content are heavily processed and often considered junk food. Maybe they like to promote the low GI factor as well?
Of note – Tim is correct – some current research suggesting improved absorption and/or greater capacity to burn ingested carbs if some is fructose. Another plus for having it in gels, etc (although it’s been in these for years anyway).
This is quite simplified, but is the basic gist. An important note (not so much for us that burn good amounts of carbs) – too much fructose is not good, in spite of what might be a good GI. Too much of it can result in negative ramifications starting from the liver, ie excess cholesterol production, fatty liver and so on.
check out www.emend.com
and www.glukos.com
in my experience, keep it simple. i like champion nutrition Revenge Sport and cliffs electrolyte drink.
the source of maltodextrine that’s in Revenge sports agrees with me. i can’t do the infinite or power bar’s endurance.
i use revenge sport on the bike and glukos on the run.