Fructose Metabolism

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By Shannon Clark

When it comes to fuel for your muscles, glucose is the body's preferred source. A diet that is relatively high in glucose, either coming from simple glucose molecules or polysaccharides, will provide the most energy for your workouts and physical pursuits.

Foods that normally contain high amounts of glucose would include bread, pastas, rice, potatoes, vegetables, candy, rice cakes, popcorn and so on.

On the flip side, there are other forms of carbohydrates that are not made primarily of glucose that will react slightly differently in the body. These forms of carbohydrates are fructose, galactose and mannose.

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In addition to that, excess triglycerides will start accumulating and you will as a result begin to experience weight gain.

Do note however that one single piece of fruit contains only about 5-8 grams of fructose so fruit consumption is not the major worry here, but rather all those other products, particularly those with HFCS that you need to be watching in the diet. Over consumption of fruit however is not recommended either as this can cause gastrointenstinal upset in many individuals.

Furthermore, if weight maintenance or loss is a concern, you only have so many calories you can consume in a day so if you are filling yourself up with fructose, you will not have as much room for glucose, which is what you want to concentrate on so that you are able to maximize the amount of energy your muscles have.

In terms of when to eat your fructose consuming foods, you should focus a small amount of them right after a workout as the liver glycogen stores (fructose levels) are what signal the body as to whether or not it is in an anabolic or a catabolic state. Since after a workout you want your body to be ready to start building and repairing muscle tissue (an anabolic process), topping up your liver glycogen stores with this fructose is a smart move.

The time you do not want to consume it then is right before a workout because that is when your muscles are going to need the most energy and you would be better off eating glucose.

So make yourself more aware of the differences between glucose and fructose in the foods you are eating and take steps to ensure you are getting the right type of carbohydrate at the right time of the day.

Fructose

Fructose is a type of carbohydrate that is largely found in fruits along with other highly processed foods like sodas, granola bars and anything with the ingredient high fructose corn syrup listed on the label.

The main difference when it comes to fructose versus glucose in terms of how they are handled by the body is that fructose is handled by the liver whereas glucose is handled by the muscles of the body. Because of this, fructose will also not effect blood sugar levels like glucose will nor will it have an effect on insulin, leptin and glucogon - all hormones that regulate appetite and blood sugar.

It should be noted as well that sucrose is about half fructose, half glucose so foods containing this will be dealt with in the body by both the muscle and liver cells.

The liver itself has a storage capacity of about 100 grams for fructose, when intake from the diet exceeds this, the liver will start to process this fructose, turning them into triglycerides and releasing them into the blood stream. This in return increases your chances for heart disease so it is definitely something you want to avoid.

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