Although sucrose, fructose, and glucose are all simple sugars that provide the body with the same amount of energy per gram, the way the body metabolizes and uses them is different.
Sucrose, fructose, and glucose are three simple sugars, i.e., they are all sweet-tasting. When you take any of them, the body gets the same amounts of calories per gram; however, there are major differences among them. For instance, the way the body absorbs each of the sugar and metabolizes it is different, and while your tongue may not differentiate one from the other, the body can perfectly do this. Sucrose, fructose, and glucose and naturally found in dairy products, fruits, and vegetables, but they are also added to processed foods to enhance their sweetness and flavor. This article explains the major differences in these three forms of simple sugar, and the information should help you know how to regulate your dietary sugar intake.
Understanding sucrose, fructose, and glucose- what are they?
First things first, let’s get to the roots and understand what sucrose, fructose, and glucose are.
The chemical structure of sucrose is outstandingly different from glucose and fructose, making it quite unique among the simple sugars. There are two types of simple sugars; monosaccharides and disaccharides, where the latter is made from two monosaccharide molecules. Sucrose contains two monosaccharides, glucose, and fructose in ratio 1:1 or 50% each. It is the table sugar, and after being taken, the body breaks it down to the constituent glucose and fructose molecules. Sucrose occurs naturally in grains, cereals, fruits, and vegetables, although it is a major component in many processed foods, including canned foods, sodas, sweetened drinks, breakfast cereals, candy, and ice creams. In the industries, sucrose is made from sugar beets or canes, and it is sweeter than glucose but less tasty than fructose.
Glucose is the body’s most preferred form of sugars, and is made of a single sugar molecule, hence the prefix ‘mono.’ When taken, the body does not break glucose into other simpler compounds but uses it as the carbohydrates building blocks. In the foods we take, glucose is rarely found on its own but is typically bound to another simple sugar, forming disaccharides such as lactose or sucrose. Glucose is the least sweet of the three simple sugars and is added to processed foods as dextrose, which is obtained from cornstarch.
Fructose is another simple sugar, which like glucose, has only one sugar molecule, hence belonging to the monosaccharide group. Like glucose, when taken by the body, fructose is not broken further because it is already in its simplest form. Fructose is naturally found in agave, honey, and root vegetables and is also featured in processed foods as high-fructose corn syrup. The industrial processes producing fructose utilize sugar beets, corn, and sugar cane, while the high-fructose corn syrup is made from cornstarch. Unlike the normal corn syrup, high-fructose corn syrup has higher fructose concentrations than glucose. Notably, fructose is the sweetest of the three simple sugars, but it least impacts your body.
Different digestion and absorption processes
The other remarkable differences in sucrose, fructose, and glucose are seen in how variedly they are digested and absorbed. Generally, monosaccharides, being in their simplest forms, are not broken down into simpler compounds; instead, they are directly absorbed into the bloodstream once in the system. Contrastingly, disaccharides must be broken down into constituent monosaccharides, and even after such a process, the metabolism that follows differs. Here is how.
a. How glucose is absorbed and used
Glucose is a monosaccharide and is directly absorbed into the bloodstream through the small intestinal linings. Once in the bloodstream, glucose stimulates blood sugar levels to rise, a phenomenon the body responds to by producing insulin to facilitate entry of the simple sugar into the cells. Notably, glucose causes the fastest rise in blood sugar levels of the three sugars. After absorption by the cells, glucose is either used directly for energy release if the body is deficient in it. However, if there is enough, the body converts the glucose to glycogen and stores it in the liver or muscles for use at a later date, i.e., during glucose deficiency when glycogen is broken down to glucose for immediate energy use.
b. How fructose is absorbed and used
Being a monosaccharide like glucose, fructose is readily absorbed into the bloodstream through the small intestinal walls. However, it takes relatively longer to raise blood sugar levels compared to glucose. Nonetheless, its effects on the body are more far-reaching than glucose because the liver must convert it to glucose for it to be metabolized. Consequently, taking too high amounts of fructose alongside a high-calorie diet may harm you when the sugar accumulates and causes a rise in blood triglycerides. As if that’s not enough, too much fructose in the body increases one’s risk for non-alcoholic fatty liver disease and metabolic syndrome.
c. How sucrose is absorbed and used
Sucrose has to be broken down to glucose and fructose before being metabolized, and the process happens partially in the mouth but is completed in the small intestines by the enzyme sucralose. Once broken down into the constituent monosaccharides, they are used as described above. It is noteworthy that the more glucose in the bloodstream, the more fructose the body absorbs, boosting fat creation. Therefore, taking these simple sugars together is more harmful than taking them separately, which is why high-fructose corn syrup has many health implications.
Limiting your added sugar intake is good for your health
The sugars found in fruits, dairy products, and vegetables are generally safe since they have water and fiber that counteract any negative impacts, provided that one takes them in moderation. This is not true for added sugars that have multiple health effects and features in most foods in the western diet. One recent survey showed that, on average, a person takes 82 g of added sugar per day, constituting 16% of his calorie intake. This is higher than the recommended value, especially now that the World Health Organization suggests that only 5-10% of daily calorie intake should be from added sugar. This means that those taking 2,000 calories per day should take only 25-50 g of added sugar. In addition, focusing on whole instead of processed foods is the best way to go, mainly because even the foods that you least expect to have added sugar, like sauces and condiments, feature it. If you have to take processed foods, read the ingredient list to know what you are taking.
Sucrose, fructose, and glucose are three simple sugars, which despite having the same energy levels per gram, are differently absorbed and used. While glucose and fructose are directly absorbed into the bloodstream, sucrose must first be broken down into fructose and glucose. Afterward, glucose is used for energy production or stored in the liver and muscles as glycogen, while fructose is first converted to glucose for similar uses. Although glucose and fructose raise blood sugar levels differently, they are discouraged, especially because fructose has other health concerns. As such, focusing on whole foods is the best way to go.