Difference between Dextrose and Sucrose

Introduction

Sugar forms part of our daily diet acting as a source of energy to the body. While some people worry that eating sugar may be bad for their health, without sugar many basic bodily functions would cease to run properly [1]. Foods are often sweetened with various types of sugars such as glucose, sucrose, fructose and so on and while it is easy to assume that that all of these are one of a kind, it’s important to look past this and beyond to the biochemistry and nutritional value of the different kinds of sugar molecules. Beyond the basic chemical structures, each of these sugar types differs based on their properties, function and availability making some better for our bodies than others.

Kinds of Sugars

There are many different kinds of sugar which form a source of fuel to the body. These are digested and absorbed differently based on their individual structure [5]. Sugar is broadly divided into three different groups, namely sugar, oligosaccharides and polysaccharides with the sugar group being further divided into classes of monosaccharides, disaccharides and polyols [1]. Monosaccharides and disaccharides form two kinds of simple sugars while oligosaccharides and polysaccharides, contain more sugar combinations and are known as complex carbohydrates.

Since monosaccharides are simple sugars, they require the least effort to be broken down by the body which means they are available for energy usage more quickly than other sugar molecules. They do not require any form of digestion. Common examples of monosaccharides include glucose, fructose and galactose. Disaccharides on the other hand are formed with two monosaccharides are joined by a glycosidic bond. Common examples include sucrose, lactose and maltose with digestion of disaccharides usually occurring in the small intestine [2].

Dextrose and sucrose

Dextrose and sucrose are both sugars and while they are similar and used in similar ways within the body, they are often confused as being identical sugars which is not true. Sugar itself is a general term while dextrose forms a specific type of sugar [2]. Sucrose is a complex carbohydrate and disaccharide consisting of two different sugar molecules.

Structure of the Sucrose Molecule

Sucrose forms a disaccharide molecule consisting of two sugar units. It contains a basic ring of glucose which is chemically combined with another monosaccharide of fructose. It has the chemical formula C₁₂H₂₂O₁₁. The official chemical name is saccharose and the conventional name is table sugar [3]. Sucrose is much sweeter as it contains both dextrose and fructose and because fructose itself, is much sweeter than dextrose alone. Sucrose is better known as table sugar which is commonly extracted from cane sugar and sugar beets.

Structure of the Dextrose Molecule

The dextrose molecule is extremely abundant in nature and can be found in numerous plant and animal tissues. Dextrose is a monosaccharide and is defined as simply being a form of glucose or a simple carbohydrate. While the terms glucose ad dextrose are used interchangeably, there is a slight difference between dextrose and glucose. Glucose is said to have two different molecular arrangements. These are known as isomers and while they contain the same molecules, the arrangement of the molecules is different such that they mirror each other. These isomers are known as L-glucose and D-glucose with the later forming the dextrose molecule.
Dextrose and glucose both consist of just one molecule of sugar which means it is made up of a single sugar ring. Thus it can be said that dextrose also forms a component of sucrose. Dextrose has a chemical formula of C₆H₁₂O₆. It usually occurs on its own as a simple sugar but it can be combined into larger molecules with additional units of dextrose to form bigger carbohydrates like starch. It can also be combined with other units of monosaccharides. Plants store dextrose as starch so it is easily extracted from corn starch to create a sweetener.

Digestion and absorption

Since dextrose has a very simple structure, it does not require any digestion and is absorbed directly into the bloodstream. Sucrose, on the other hand, is far too large for direct absorption and requires digestion using the enzyme sucrase which is found in the small intestine. Sucrose is broken down into monosaccharides before being adsorbed into the bloodstream. Once these monosaccharides are adsorbed, these units that are initially broken down from sucrose will act in the same way as pure dextrose molecules. After adsorption into the blood stream, the hormone insulin steps in to aid the uptake of glucose into the cells where it is then metabolised into energy for immediate use.

Cellular Use

Dextrose and broken down sucrose monosaccharides are used for a variety of purposes. They can be burnt for immediate energy or converted into glycogen or fat and stored until needed by the body. To conserve and store fuel, the body converts excess glucose that is not needed immediately into glycogen which forms a carbohydrate that is stored in the liver and muscles. Glycogen provides extra blood sugar when levels are running low usually during meals, at night while sleeping or during intense physical workouts. Through glycogenesis, the liver creates glycogen chains containing hundreds of glucose molecules which are connected through chemical bonds. The body will then break down the glycogen for energy when primary sources are not available to prevent drops in blood sugar. Fat on the other hand provides long tem energy storage. Despite forming one of the main energy sources, excessive consumption of glucose may lead to Type 2 diabetes. Dextrose on the other hand is specifically used in intravenous fluids to treat dehydration or to provide extra calories when complex carbohydrate foods are consumed.

Energy Production

The main purpose of both sucrose and dextrose is to provide a source of energy to the body. When consumed, dextrose is ready to be adsorbed into the bloodstream while digestive enzymes are required to break apart sucrose before adsorption. This slows down the digestion of sucrose which in turn results in a steadier blood sugar level and sustained energy levels. In addition, since sucrose forms a complex carbohydrate; it is also able to provide more vitamins and minerals than dextrose which forms a simple sugar that causes sharp jumps in blood sugar levels.

All sugar molecules have the potential to affect blood sugar but they affect it differently. Blood sugar levels are commonly measured by the glycaemic index. This index rates food according to how quickly they increase blood sugar levels with pure glucose at a score of 100 and plain sucrose at a score of 68. Molecules that have a score of 70 or higher indicate that a large jump in blood sugar will occur. Therefore it can be said that glucose will cause a quick and large jump while sucrose on the other hand only has a moderate effect on the blood sugar levels. Most fruits and vegetables contain varying amounts of dextrose and sucrose however the fibre content found in respective fruit and vegetable sources will change the overall glycaemic impact of the individual sugar types [3]. Fibre is known to slow down carbohydrate digestion so dextrose and sucrose can enter the bloodstream at a more gradual pace.

Commercial Sources and uses

Most commercial sources of sucrose come from the natural sugar content of sugarcane or sugar beets. These natural sugars are refined to different degrees to produce different varieties of granulated, powdered or brown sugar as well as speciality sugars like muscovado. In additions some by-products are used in the production of molasses [4]. Dextrose on the other hand is manufactured commercially from corn starch and can be obtained from starchy sources such as maize, rice, wheat and cassava. Dextrose is much less sweet than sucrose and is commonly used as a sweetener in many packaged and processed foods because it is affordable and commonly available. It is also used to stabilize food colourings and to extend the shelf-life of packaged foods.

Table 1: Summary of major differences between dextrose and sucrose