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 misconception 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 (except melons), milk and yoghurts. Many starchy foods have a high GI including most flours and breads, potatoes (except Carisma), rice (except Doongara), rice crackers and other savoury snacks (e.g., pretzels) and many crunchy breakfast cereals (puffed rice, flaked corn and wheat).
Whilst excessive energy intake (kilojoules) from foods and drinks containing large amounts of added sugar should be avoided, you should consider more than sugars alone when making food and drink 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 and wellbeing.
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
Rice syrup GI=98
As can be seen, sucrose has a medium GI, so addition of large amounts will raise (not lower) the GI of most foods and drinks.
Added sweeteners in Australian foods
In Australia, maltodextrins (currently not listed as sugars in the Nutrition Information Panel) are the most common form of sweetener added to foods, followed by sorbitol (a polyol), lactose (milk sugar), invert sugar and sucrose (both forms of 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…).
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 converted to glucose and stored as glycogen (a form of starch) 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.
Added sugars and the GI Symbol Program
The GI Symbol Program includes category specific nutrient criteria that incorporate energy (kilojoules), total carbohydrate, total and saturated fat, sodium, and in certain categories dietary fibre and calcium. The energy and carbohydrate caps and dietary fibre requirements limit the amount of sugars that can be added to foods.