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GI and Sugar

Total Carbohydrates more important than sugars alone.

The Glycemic Index (GI) is simply a measure of how quickly a carbohydrate food raises blood glucose levels. Carbohydrates (both sugars and starches) are arguably the most important source of energy for our bodies.  Low GI carbohydrates – those that are slowly digested, absorbed and metabolised – cause a much lower and slower rise in blood glucose and insulin levels, helping us to burn more fat and avoid weight gain over the longer term.

It is a common mis-understanding that all sugars have a high GI and all starches have a low GI.  In fact, many sugar-containing foods also have a low GI.  Examples include most fresh, dried and canned fruits, milk, flavoured milk drinks and yoghurts.  Many starchy foods have a high GI including white flour and white flour breads, potatoes, Jasmine rice, rice crackers, and many breakfast cereals (puffed rice, flaked corn and wheat).

Whilst excessive energy (kilojoule) intake (>10% of energy) from foods and drinks that are high in added sugars should be avoided, consumers should consider more than sugar content alone when making food choices.  It is important to consider the total amount of carbohydrate and its GI rating and the overall nutritional quality of a food including the amount of kilojoules, fat, saturated fat, salt and fibre for long term health outcomes.


Sugars and GI

The glycemic index (GI) of sugars ranges fivefold from a low of 19 for fructose to a high of 105 for maltose (see table 1 for details).

Table 1: GI of sugars

Maltose GI= 105
Glucose/dextrose GI=100
Rice syrup GI=98
Sucrose GI=65
Lactose GI=46
Fructose GI=19

As can be seen, sucrose has a medium GI, so addition of large amounts will raise (not lower) the GI of most foods and beverages.


Added Sweeteners in Australian Foods

In Australia, the most common sugar added to foods and drinks is sucrose (otherwise known as cane sugar). Fructose is very rarely added to foods in Australia due to its high cost, overly sweet taste (1.7 times sweeter than cane sugar) and the fact that large amounts consumed by itself will cause malabsorption (bloating, gas, pain, nausea, diarrhoea, etc…).

Added sugars consumption decreased between 1995 and 2011/2.



As the GI value indicates, 19% of pure fructose consumed in a 50 g dose is directly converted into glucose in the liver and released into the blood stream over a 2 hour period. The remainder is stored as glycogen (a form of starch) in the liver for later use, or released into the blood stream as pyruvate, lactate or triglycerides. Unlike rodents, very little fructose is converted to fat in humans.


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