Sucrose is the chemical name for common white table sugar that’s found in diners, coffee shops and kitchen cupboards the world over. It naturally occurs in many fruits and vegetables, although sugar cane and beets are the sources most used for its commercial production. Sucrose is readily metabolized by your body and used for energy, although too much at a time spikes blood sugar levels and insulin release while promoting fat storage.
Sucrose is a type of carbohydrate called a disaccharide, which is a variety of sugar. It's composed of two simpler sugars, or monosaccharides, called glucose and fructose. Glucose is the end-product of carbohydrate metabolism and used by virtually all cells, especially your brain, to produce energy and do work. In fact, people often get a little cranky or foggy when glucose levels get low because it’s the primary fuel for your brain. Fruits and vegetables contain a variety of complex and simple sugars, which all have different levels of sweetness. Sucrose is sweeter than pure glucose, but not as sweet as pure fructose or fruit sugar, which makes sense because it’s made of equal amounts of each. Compared to milk sugar, or lactose, sucrose is five times sweeter.
Sucrose doesn’t get broken down until it passes out of your stomach and enters your small intestine. Once there, the intestinal lining releases an enzyme called sucrase, which cleaves sucrose into one molecule of glucose and one molecule of fructose. From the small intestine, glucose is quickly absorbed into your bloodstream and transported to the far reaches of your body. In contrast, fructose requires a little more enzyme work in the liver before it’s reduced into glucose.
Sucrose can’t provide any energy until it’s metabolized into glucose. However, once cleaved by sucrase, some glucose is free to enter your cells with the help of insulin and begin a series of reactions which eventually produce a chemical called pyruvate. Pyruvate is then transformed into an energy storage molecule called ATP, which can be used immediately to power the cells' processes or stored for later use. Overall, sucrose provides a relatively quick source of energy and yields almost 4 kilocalories per gram. Some important nutrients needed for the oxidation of sucrose include vitamin C and most of the B vitamins.
Because sucrose is metabolized so readily, it quickly impacts blood glucose levels and triggers insulin release. Consequently, table sugar has a high glycemic rating of about 80, which is a measure of how quickly a substance impacts blood sugar and insulin release. For comparison, raw honey has a glycemic index of about 30, whereas high fructose corn syrup is rated at 87. As such, diabetics need to be careful and limit their use of sucrose. Even for those without diabetes, high levels of sucrose consumption are linked to tooth decay, obesity and cardiovascular disease.
- Advanced Nutrition and Human Metabolism; James L. Groff et al.
- Human Metabolism: Functional Diversity and Integration; J. Ramsey Bronk
- Human Biochemistry; Charles Dreiling
- Encyclopedia of Human Nutrition; Benjamin Caballero et al.
Sirah Dubois is currently a PhD student in food science after having completed her master's degree in nutrition at the University of Alberta. She has worked in private practice as a dietitian in Edmonton, Canada and her nutrition-related articles have appeared in The Edmonton Journal newspaper.