All about sugar

Sugar has had bad press, as a nutrient for humans.  So, what is the truth?

In one sentence: We all have sugar, in the form of glucose, in our blood.  We absolutely need glucose, we would not survive as our brain constantly needs glucose for energy to work.

Our blood glucose level is maintained by hormones, so that it does not get too high or too low. Insulin is a hormone that regulates glucose when the levels are too high, it gets released from our pancreas to remove the glucose from our blood.  When glucose is stored in our bodies, it is converted into glycogen.  If glucose concentration in the blood begins to get too low, a range of potent hormones are released to push it up again.  These include glucagon, cortisol, adrenaline, growth hormone.  Together they make our cells release the stored glucose (glycogen) from the tissues into our blood when we need that energy source.

Because carbohydrates are the closest form to glucose, we are able to use carbs quickly and easily as our first source of energy.  If you try to reduce your carbohydrate consumption and you do vigorous exercise, the process is longer and more complex for your body.

The Glycaemic Index

The glycaemic index (UK) or glycemic index (USA) is a measure of how quickly blood glucose levels rise after eating a particular type of food.  The benchmark is glucose, which has a glycemic index of 100. The effects that different foods have on blood glucose levels vary considerably. The glycemic index estimates how much each gram of available carbohydrate (total carbohydrate minus fibre) in a food raises a person’s blood glucose level following consumption of the food, relative to consumption of pure glucose.

Foods with carbohydrates that break down quickly during digestion and release glucose rapidly into the bloodstream tend to have a high GI; foods with carbohydrates that break down more slowly, releasing glucose more gradually into the bloodstream, tend to have a low GI.


ClassificationGI RangeExamples
Low GI55 or lessbeans (e.g. kidney, lentil, soy, almond, peanut, walnut, chickpea); small seeds (e.g. sunflower, flax, pumpkin, poppy, sesame); most whole intact grains (durum/spelt wheat, millet, oat, rye, rice, barley); most vegetables, most sweet fruits (peaches, strawberries, mangos); fructose
Medium GI56 to 69not intact whole wheat or enriched wheat, pita bread, basmati rice, unpeeled boiled potato, grape juice, raisins, prunes, pumpernickel bread, cranberry juice, regular ice cream, sucrose, banana
High GI70 or moreConfectionery, white bread, most white rice, corn flakes, sweet breakfast cereals, glucose, maltose, maltodextrins, potato, parsnip, bagels