Low GI stands for Glycaemic Index
Gly – means glucose
Aemic – means blood
Index – means “measure of something”
So when we put it all together it means “measure of glucose in the blood”.
And when we are referring to the Glycaemic Index of a certain food we are referring to the effect that food has on the glucose level in our blood when we eat it.
When we eat foods containing carbohydrate, through the process of digestion we break the carbohydrates down into their simplest form – glucose.
A high GI food’s carbohydrate is broken down into glucose quickly and released quickly into the blood after eating it causing a blood glucose “spike”. We might also refer to these foods as “fast release” or “quick burning”.
A low GI food’s carbohydrate is broken down into glucose slowly and released slowly into the blood after eating it, giving a more gradual rise in blood glucose levels. We might also refer to these foods as “slow-release” or “slow-burning”.
There are 3 classifications for ranking the GI of foods:
Low = less than 55
Moderate = 55 to 70
High = more than 70
Different things influence and affect the glycaemic index of the foods we eat.
HOW PROCESSED THE FOOD IS
In general, the more refined or processed a food is, the higher the GI will be. This is mostly due to the natural fibre of the food being removed during the manufacturing process leaving the starch highly susceptible to digestive enzymes, allowing it to be rapidly converted into glucose.
FAT AND ACID
The more fat or acid contained in a meal, the lower the glycaemic index of that meal will be because the fat and acid slow down the emptying of the meal from the stomach into the small intestine where the glucose is absorbed.
THE CHEMICAL STRUCTURE OF THE SUGAR
Not all sugar is just “sugar”. The sugar that we all know as the white granular crystals we put in our tea or coffee is actually called sucrose. Sugar derived from fruit is known as fructose and the sugar found in milk is lactose. Each sugar (ie. sucrose, lactose, fructose) differs slightly in chemical structure making them unique. It is this chemical structure that affects the rate at which we digest and absorb the sugars.
The longer we cook a starch, the higher the GI gets. For example, the glycaemic index of al dente pasta is 45, while the same pasta cooked for 5-10 minutes longer has a higher GI of 65. This is due to the increased water content of the pasta the longer its cooked. This increased water content speeds up the digestion of the carbohydrate resulting in a faster release of glucose into the blood. Some other foods where the glycaemic index is affected by cooking time are potato, sweet potato and rice.
THE BENEFITS OF A LOW GI DIET
A low GI diet stabilises blood glucose levels, or as mentioned previously, prevents blood glucose “spikes”. The body responds to high blood glucose levels by producing more of a hormone called insulin. One of the functions of insulin is to move glucose out of the blood and into the cells of your body where it is used for fuel. High blood insulin levels can lead to insulin resistance which can make it more difficult for the body to break down stored fat to use for energy when you are in a calorie deficit. In this way, following a low GI diet is helpful in your efforts to lose weight.
A low GI diet also helps to keep you feeling fuller for longer, leading to less overeating. Researchers at Kings College London were able to show that this is due to the increased production of a hormone called GLP-1 [glucagon-like peptide 1] after the consumption of a low GI meal1. GLP-1 is a hormone produced in the gut that is known to cause increased feelings of fullness and appetite suppression.
So, including at least one low GI food at each of your meals and snacks may help you to feel fuller and more satisfied for longer after eating, give you a more sustained energy release and keep the levels of glucose and insulin in your blood within the optimal range.
WHICH FOODS ARE LOW GI?
Bread and crackers – wholegrain, rye, sourdough
Cereal – porridge, rolled oats, muesli
Grains – quinoa, barley, pearl couscous, buckwheat, semolina
Rice – Basmati, Mahatma, Doongara (Clever Rice), long-grain rice, brown rice
Pasta and noodles – pasta, soba noodles, vermicelli noodles, rice noodles
Legumes – all dried and canned legumes. Examples include lentils, chickpeas, soybeans, kidney beans, baked beans.
Starchy vegetables – Nicola and Carisma potatoes, orange sweet potato, corn
Fruit – most fruits are low GI except for rockmelon, watermelon and lychees.
Dairy – milk and yoghurt are naturally low GI.
If you would like to know the GI of your favourite food, try looking it up using this handy tool from the University of Sydney.
Reference: 1. Society for Endocrinology. (2009, March 18). Scientists Discover Why A Low GI Meal Makes You Feel Full. ScienceDaily. Retrieved July 21, 2019 from www.sciencedaily.com/releases/2009/03/090317201139.htm