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Sucrose vs Glucose vs Fructose: What's the Difference?

Dr. Pravallika Devisetti

5 Min Read

Fast Check Fact Checked

Have you ever wondered when your doctor or fitness trainer asks you to cut down on sugar, what do they actually mean? Well, there are three different types of sugar that are naturally found in fruits, vegetables, dairy products and grains – Sucrose, Glucose and Fructose. These sugars are also added to many processed food items.

You must be wondering whether the type of sugar matters. Yes, and excessive consumption of these sugars can be dangerous. These sugars differ in chemical structures and the way the body digests and metabolizes them and their impact of them on our health.

Sugars are generally categorized into monosaccharides or disaccharides. Monosaccharides are the simplest sugar forms made of one single unit of sugar. Glucose and fructose are monosaccharides. Sucrose is a disaccharide that is made of glucose and fructose. Sucrose, glucose and fructose are simple carbohydrates. In this article, let us understand the difference between these three and how they impact our health.

Fructose:

Fructose is a monosaccharide that is considered to be the sweetest naturally occurring sugar in fruits and vegetables and it is used in beverages or flavored drinks. It is a single sugar molecule that is made of 6 carbon atoms, 6 oxygen atoms and 12 hydrogen atoms. Fructose has a high level of sweetness when compared to other sugars. Often it is observed that individuals who use fructose in cooking require small amounts for achieving appropriate sweetness.

Fructose is commonly found in fruits, different vegetables, fruit juices and honey. Fructose is metabolized only in the liver. Fructose needs conversion to glucose in the liver via glycolysis to become an energy source for your body. Fructose is also involved in lipogenesis causing fat production in the body leading to high triglyceride levels and also non-alcoholic fatty liver disease. This can cause atherosclerosis which is the growth of fat-filled plaques which accumulate in the walls of arteries that cause cardiovascular diseases and stroke. These are found to happen in individuals with an intake of chronic high fructose diets.

Glucose:

Glucose is one of the most important monosaccharides that is preferred as an energy source. Glucose is known as blood sugar. This is absorbed directly from your intestine. After glucose is absorbed into the bloodstream, insulin is secreted primarily in response to the elevated blood concentration of glucose and insulin facilitates the entry of glucose into cells.

Glucose relies on glucokinase or hexokinase for metabolism. Once glucose enters the cells it is either to be used immediately for energy or stored in muscle cells or in the liver for future use. The body processes most carbohydrates you eat into glucose. Glucose stimulates insulin release from the pancreas and causes the secretion of hormones i.e. leptin and ghrelin. A Glycemic index is a number assigned to foods based on how quickly and how high these foods can make the blood sugar level rise after eating them. High GI foods are easily broken down to glucose and increase the blood sugars quickly.

Sucrose:

Sucrose is a disaccharide. Sucrose is the scientific name for table sugar which is composed of one glucose and one fructose molecule that is equal amounts of glucose and fructose. Table sugar and other forms of sucrose are extracted from sugarcane and beets. Sucrose tastes less sweet compared to fructose but is sweeter than glucose. Sucrose is a naturally occurring carbohydrate and is found in different vegetables, fruits and grains. Sucrose is also added to processed foods like candy, breakfast cereals, ice cream and even sweetened beverages.

Sucrose is metabolized in the liver. Due to Glucose content, sucrose can cause an elevation in blood sugar.

Sucrose, Fructose and Glucose are absorbed differently:

The body digests and absorbs monosaccharides and disaccharides differently. Monosaccharides are in their simplest form and do not require to be broken down and are absorbed into the bloodstream. Disaccharides such as sucrose must be broken into simple sugars prior to their absorption from the intestine to the bloodstream.

Glucose absorption & use: Glucose is absorbed directly via the lining of the small intestine into the bloodstream which is further delivered to cells with the help of insulin secreted in response to elevated blood glucose levels. Once glucose is taken up by the cells it is used for energy immediately or stored in muscle cells and the liver for future use. When blood glucose levels fall your body uses the glucose stored in the liver.

Fructose absorption & use: Fructose is absorbed directly into the blood from the small intestine. Fructose gets metabolized in the liver. Fructose raises blood sugar levels slower than glucose and it does not immediately impact insulin levels. Even though fructose does not increase blood sugar levels immediately it has long term negative effects. Excessive fructose intake can cause high triglyceride levels in the body and raise the risk of metabolic syndrome and non-alcoholic fatty liver disease etc.

Sucrose absorption & use: As sucrose is a disaccharide it needs to be broken down into monosaccharides for its absorption from the intestine. Enzymes in the mouth and majorly in the small intestine an enzyme named sucrase breaks sucrose into glucose and fructose. This enzyme is made by the lining of the small intestine.

These monosaccharides are then absorbed into the bloodstream. The glucose stimulates insulin secretion which helps glucose to enter the cells which are used for energy and fructose is taken up by the liver. As there is insulin secretion by the glucose here, fructose is converted into glucose and fat by insulin which does not happen when fructose is consumed alone in the absence of glucose. Hence, the effects of fructose on your body are more when consumed along with glucose (Sucrose) than when eaten alone.

After understanding the three different types of sugar, it is important to know which type of sugar is the worst for your health. Remember, any kind of sugar in excess is harmful to your health.

Your body converts fructose into glucose in the liver for using it as a source of energy. Excess fructose gets converted to fat, and triglycerides. Also consuming fructose can cause feelings of hunger and sugar cravings. Fructose thus when consumed in excess can cause harmful effects such as insulin resistance, type 2 diabetes, obesity, non-alcoholic fatty liver disease etc. Consuming a high fructose diet for a long time can increase the risk of cardiovascular disease and stroke. These negative effects are more when fructose is consumed along with glucose (i.e. Sucrose) than when fructose is consumed alone.

Any kind of sugar in excess can cause harm to your heart, the liver can cause weight gain, hypertension and many other health hazards. In order to ensure a healthy diet, you must eat whole foods, grains & nuts and include seasonal fruits and vegetables in your diet. Make a habit of reading food labels and always ensure you avoid the intake of processed foods.

For long & healthy life, focus on important pillars of your health – A healthy balanced diet, Exercise 150 minutes/week, Adequate sleep, Stress management, and preventive health checkups.

If you are facing any health issues, you must get in touch with the doctors and take relevant treatment and cut down on sugar & unhealthy diet consumption with customized appropriate dietary advice from dietitians. Here at MFine we always focus on guiding you towards a healthy life. In case of any health issues consult our doctors and dietitians at MFine for the best advice on health & diet.

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