Does the Body Burn Glucose and Fructose?
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Carbohydrates are a class of nutrients that contain carbon atoms and water molecules. They include sugars, starches and fiber. The body breaks down sugars and starches in food into the simple sugar known as glucose, which then circulates in the bloodstream. Glucose supplies the body’s cells with fuel for the energy they need to function. Fructose – another carbohydrate – is a simple sugar naturally found in fruits. Both glucose and fructose are carbohydrates your body needs to produce energy.
Simple Carbohydrates
Simple carbohydrates contain just one or two saccharides, or sugar molecules. Examples of simple carbohydrates are sucrose, or table sugar, and lactose, a sugar in milk. Unlike sucrose, which includes one molecule of glucose and one of fructose, lactose is made up of glucose and galactose. Because the chemical structure of simple carbohydrates consists of one or two sugar molecules, these simple sugars are easy for your body to break down into glucose and convert into energy.
Monosaccharides
Monosaccharides are the simplest form of carbohydrates. Glucose and fructose are examples of monosaccharides. The body absorbs monosaccharides – single units of sugars and starches – into the bloodstream through the small intestine. Glucose, fructose and galactose are simple sugars that the body continuously coverts into glucose. Before your body can use fructose, the liver must first convert it into glycogen – a glucose molecule that is stored in the liver and muscle cells for later energy release. When your blood sugar level drops, the liver quickly converts glycogen into glucose.
Complex Carbohydrates
Complex carbohydrates, also known as polysaccharides, are made of long strings of simple sugars. These nutrients are generally referred to as starches; the body breaks them down into glucose like it does simple sugars. Because it takes more time to digest starches, these sugars cause fewer fluctuations in blood glucose levels. Although the fructose in fruits is a simple carbohydrate that the body digests quickly, fruits also contain fiber and a number of essential vitamins and minerals.
Glucose vs. Fructose
Glucose is the body’s first choice as an energy source, although it may respond differently to fructose than it does to glucose. Another factor to consider when it comes to healthy nutrition is that most of the commercial food products you eat contain high-fructose corn syrup or sucrose rather than glucose. Findings of a study reported in the May 2009 issue of the “Journal of Clinical Investigation” suggest that overconsumption of fructose-sweetened products can lead to weight gain and increase the risk of developing heart disease and diabetes.
Sources
Whole grains, vegetables, fruit, milk and dairy products are healthy sources of the carbohydrates your body uses to make glucose. Other foods that are high in carbohydrates include those to which sugar has been added. Foods made with white flour and added sugars usually supply fewer nutrients than those that provide dietary fiber. Fructose is naturally found in honey, most fruits and many vegetables. Some fruits with high fructose content include grapes, apples, cherries, pears, watermelon and honeydew.
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References
- AskDrSears.com: Sweet Facts You Should Know About Sugar
- Centers for Disease Control and Prevention; Carbohydrates; February 2011
- “Journal of Clinical Investigation”; Consuming Fructose-Sweetened, Not Glucose-Sweetened, Beverages Increases Visceral Adiposity and Lipids and Decreases Insulin Sensitivity in Overweight/Obese Humans; Kimber Stanhope, et al.; May 2009
