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What is the function of sugar in the body?

Naturally occurring sugars play an important role in providing energy and a variety of nutrients the body needs to remain healthy. Many of the foods we eat contain a range of sugar types. For example, a wide variety of fruits and vegetables contain sugars including fructose, glucose and sucrose along with fibre and many essential vitamins and minerals. Milk and cheese are high in lactose – another type of common sugar found in many dairy products. 

No matter the types of foods we consume, our bodies break down all food into simpler components, like glucose, for our bodies to use as an immediate energy source or stored as glycogen in our liver and muscles as an energy reserve for later use. A certain amount of sugar is needed for our bodies to function properly; however, excess sugar consumption from highly processed, nutrient-poor foods has been linked to a range of conditions including tooth decay, weight gain and obesity and their related conditions heart disease and diabetes. 

Naturally occuring sugars are part of a healthy eating plan and are critical for many functions in our body. Below are some of the functions naturally occurring sugars play in our body. 

Our bodies use sugars as a fuel source

As we digest the foods we consume our bodies break it down into simpler components called monosaccharides that are then distributed throughout the body. One of the most common monosaccharides the body creates from digested foodstuffs is glucose. Glucose is the principal energy source of our brain. Without it, brain functions such as thinking, memory and learning are inhibited. Glucose is converted to glycogen for later use.

The process of deriving energy from glycogen stored in our cells is called Glycolysis. During Glycolysis, the body extracts glucose from glycogen and converts it into pyruvate and lactate that supply energy to cells via a process called the citric acid cycle (also called the Krebs cycle) when there is a ready supply of oxygen in the body (aerobic respiration) or via a fermentation process when oxygen is lacking in the body (lactic acid). 

Our bodies store excess sugars for energy

When we consume more dietary carbohydrates than our bodies can use as a fuel source, our bodies will convert these excess sugars into glycogen. Glycogen is stored in our liver and muscle and is stockpiled by our bodies as an additional energy source to use when our blood sugar levels are low or during intense, intermittent exercise. 

At any given time we will have approximately 4g of glucose circulating in our blood. Our liver will store approximately 80g of glucose to help replenish a stabilised blood glucose concentration of between 4.0 and 5.5 mmol/L (70–100 mg/dL).

Sufficient sugars in the body help maintain muscle mass

Even though our bodies prefer to burn dietary carbohydrates as an energy source over fats or proteins, when the ready supply of sugars and stored glycogen aren’t available, our bodies will turn to alternative fuel sources. 

As an example, the amino acids from your dietary protein can be used to supply energy to tissue and muscles. When amino acids are used as a fuel source the protein you consume won’t be available for building muscle or maintaining current muscle mass. 



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