Glycaemic Index
Understand how the Glycaemic Index works, and you can make simple changes to your daily diet to eat healthily and be full of energy. It can help you to overcome food cravings, and avoid overeating and possible weight gain. And it can help to avoid the possible onset of diabetes.
What is it?
The Glycaemic Index (GI) is a way of ranking individual foods according to the effect they have on blood sugar levels, that is, how quickly they are digested. The rate at which mixed foods are digested depends on the total amounts of fat, protein, carbohydrate and fibre they contain, with the carbohydrate component in particular affecting blood sugar levels.
How will I benefit?
Foods with a low GI ranking cause a slow, steady rise in blood sugar levels, and high GI foods cause a rapid rise. If you eat a low GI food at the same time as a high GI food, the overall effect will be a combination of the individual effects — a moderate rise in blood sugars. Rapid rises and falls in blood sugar affect energy levels and cause cravings, so can trigger overeating.
Processing, refining and cooking food makes the carbohydrate more digestible, but it also raises the GI ranking. High-fibre and natural wholefoods (whole grain or whole wheat) take longer to digest and so have a lower GI. These foods raise the blood sugar level slowly, making them the best choice for people with diabetes and those seeking to manage their weight and improve their overall health.
Achieving a balance between high and low GI foods helps us to select a healthier diet. Including more low GI foods in your diet will provide a feeling of fullness and control post meal highs and lows in blood sugar levels.
Why are carbohydrates important in a balanced diet?
Carbohydrate foods form an essential part of a balanced diet. They supply glucose, which is the preferred energy source for the brain. They are also an important source of vitamins and minerals, vital for good health.
The carbohydrates food group includes sugars, starches and fibre. Dietary sources of carbohydrates include bread, cereals, rice, pasta, chapattis, yams, plantains, fruit, legumes, potatoes and other root vegetables — these are starchy carbohydrates. Foods which contain higher levels of sugars include cakes, biscuits, pastries, sugary drinks, ice cream and confectionery, and should only be eaten in moderation and not every day.
Diabetes and GI
Understanding how different types of carbohydrates affect blood sugar control is particularly important for people with diabetes. This is a condition in which the amount of sugar in the blood is too high due to insufficient insulin production. For this reason, people with diabetes are advised to cut down on sugary foods. Some scientific studies have shown that meals containing low GI foods are helpful for managing the diabetic condition by improving both blood sugar and fat metabolism. Epidemiological studies have also identified that diets which favour low GI foods are an important factor in actually preventing the onset of Type II diabetes.
How to incorporate GI into your eating plan
Because we eat many different types of foods over the day it is the overall balance of foods that is important, not just individual GI ranking. Examples of low and high GI foods are given in this fact sheet.
How the GI is measured
Pure glucose has a value of 100 because it produces the greatest rise in blood sugar levels. All other foods are ranked from 0 to 100 according to their effect on blood sugar levels.
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High GI – 70 or more·
Medium GI – 69 to 56·
Low GI – 55 or lessHigh GI foods:
White bread, pure fruit juices, highly refined breakfast cereals, baked potatoes, croissants, beetroot, parsnips, dates, bananas.
Medium GI foods:
Honey, ice cream, new potatoes, jam, couscous.
Low GI foods:
Apples, apricots, cherries, grapefruit, oranges, peaches, pears, sweet potato, sweetcorn, peas, chick peas, butter beans, kidney beans, baked beans, lentils, barley, bulgar wheat, basmati rice, porridge oats, muesli.
Low GI breakfasts:
Add sliced fruit to whole grain breakfast flakes.
Milkshake made from semi-skimmed milk with fresh fruits.
Fruits such as peaches and raspberries, sliced and mixed with low fat natural yogurt.
Porridge with raisins.
Mixed grain bread with avocado or Marmite.
Low GI lunches:
Flat bread with houmous and tomatoes.
Fresh fruit salad with natural low fat yogurt.
Green salad with cooked pulses and whole grain bread.
Jacket potato with baked beans and a sprinkle of cheese or sunflower seeds.
Low GI dinners:
Spaghetti bolognese with a green salad.
Stir fry chicken breast with mixed green vegetables and noodles.
Grilled steak with new potatoes, sweetcorn and peas.
Spicy dahl with rice and chutney.