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-   -   fructose question (http://www.catalystathletics.com/forum/showthread.php?t=196)

kevin mckay 11-19-2006 05:00 PM

fructose question
I have heard glucose goes more towards muscle glycogen stores and fructose more towards liver stores and excess is converted into fat. My question is what else are liver glycogen stores normally used for if not fueling muscle?

Ben Kaminski 11-20-2006 09:53 AM

Fueling the brain, I think.

Scott Kustes 11-21-2006 06:01 AM

As I recall, liver stores can be used for any needs within the body, from fueling the brain to fueling muscles. Liver glycogen is available to the entire body, while muscle glycogen is available solely to the muscle.

Bo Bolund 06-15-2007 04:53 AM

It keeps blood glucose stable.

Paul Kayley 06-16-2007 02:56 PM

One of the liver's many functions is to act as a central reservior of glucose, stored as glycogen. The glycogen in the liver is released in response to low blood sugar levels, signalled by the pancreatic release of glucagon. The blood sugar will be used for many metabolic purposes. Glucose derived from digested foods, tends to pass straight through the portal system (the blood supply to the liver from the intestines) and into the blood. Whereas fructose and galactose are captured by the liver, therefore preferentially restocking liver glycogen stores. Sugars will only be converted into fats when all the body's sugar stores are fully loaded. This takes some doing... as the mass action effect kicks in resulting in increased sugar metabolism to burn the excess sugar intake.

The muscles take their glucose supply from either their own store -muscle glycogen, or directly from the blood (Type1 fibers are better at this as they have high capillary density and glucose transporters along their membrane compared with type2 fibers). Muscle glycogen is trapped in the specific muscle cell and cannot be shared with other cells due to the absence of a key enzyme needed for its release (IIRC = glucose-6-phosphate).

Some of the above is of course dependent upon whether you have a predominately glucose based system, or a ketone based system!

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