All Sugars Are Not Created Equal: the Effects of Glucose Versus Fructose on the Human Body

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All Sugars are not Created Equal:
The Effects of Glucose versus Fructose on the Human Body

All Sugars Are Not Created Equal:
The Effects of Glucose versus Fructose on the Human Body

Sugar has occurred naturally in our environment since the dawn of time, and mankind has been enjoying its sweet taste almost that long. After all, glucose occurs naturally in corn, fructose is the natural sweetener found in fruit, sucrose occurs naturally in sugar beets and cane, and lactose is found in milk. They all taste "equally" sweet on the tongue, but our bodies can tell the difference between these monosaccharide's, and they most certainly don't have equally beneficial effects. Recent studies comparing how human bodies respond to simple sugars show that consuming fructose poses a greater risk of heart disease, diabetes and obesity than consuming equal amounts of glucose. This paper compares and contrasts these two simple sugars from their chemical composition and structure to the different ways that each is digested and metabolized within the human body. Structural Differences

Despite the fact that glucose and fructose share the same chemical formula, C6H12O6, making them both hexose sugars, their atoms are configured differently, making the two structural isomers. Glucose has 5 atoms of Carbon and one atom of Oxygen in a ring, making it a pyranose sugar. In contrast, fructose has 4 atoms of Carbon and one atom of Oxygen, making it a furanose sugar. The pyranose form is more thermodynamically stable than the furanose form (Carey, 2006). This fact can be seen most readily by the distribution of the two forms in solution. Structurally the two isomers look like this: Glucose Fructose

The differences don't end there. Glucose has an aldehyde group (--CHO), at position 1 making it an aldohexose. Fructose, on the other hand, has a ketone group (--O--), at position 2 making it a ketohexose. Aldehyde groups can be oxidized to yield carboxylic acids and are thus classified as reducing sugars. Ketone groups can also be reducing sugars but must first isomerize into aldoses via an endiol intermediate (Carey, 2006). Glucose Overview

"Glucose is the most common type of sugar, and the primary form of sugar used in the human body " (Kepos, 2008) . It is used as an energy source in the body through either aerobic or anaerobic respiration or fermentation. It is the primary source of energy for the brain and is thus extremely important to various psychological processes. In addition, glucose is critical in the production of proteins and in lipid metabolism, and as a precursor for vitamin C production. It is modified for use in these processes by the glycolysis pathway (McMurray, 1988), which will be discussed later. Glucose is absorbed directly into the bloodstream through the intestinal lining and can be sent directly to organs like the brain and used for energy. If energy is not needed immediately, glucose can be easily converted by insulin into glycogen and stored in the liver and muscles for later use, or it can be converted and stored as fat. Glucose is found naturally in grapes, corn, wheat, barley and most plant saps. It is also found naturally bound to fructose (as sucrose) in sugar cane and sugar beets. Fructose Overview

Fructose must first be converted to glucose for use in the human body. Like glucose, it is primarily absorbed through the intestinal lining, but rather than entering the bloodstream directly, it is transported through the portal vein to the liver. Unlike glucose however, some of the unabsorbed fructose is transported into the large intestine where it is fermented by colonic flora. Hydrogen is produced during this process and dissolves into the bloodstream where it is transported to the lungs and exhaled (Skoog & Bharucha, 2004). The colonic flora also produces carbon dioxide, short chain fatty acids, organic acids...
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