The Glycaemic Index

Web Resource Last Updated: 05-10-2020

The rate at which carbohydrate impacts on your blood glucose level depends chiefly on the amount of carbohydrate you have consumed (the carbohydrate load) and, to a lesser extent, the type of carbohydrate you have consumed (the glycaemic index).

The glycaemic index (GI) is a scale from 1 to 100 that is used to measure how quickly foods that contain carbohydrate raise blood glucose levels. Foods that contain carbohydrate are given a GI value; foods that have little or no carbohydrate, e.g. cheese, meat, fish and eggs, will have no GI value.

Carbohydrate foods that break down quickly during digestion raise the blood glucose more quickly, and have a higher GI value (greater than 70). Foods that break down more slowly during digestion raise the blood glucose more slowly and so have a lower GI value (less than 55).

Mixing foods with different GI values creates a new GI for the meal. Swapping high-GI foods for medium-GI or low-GI options may help you to control your diabetes better, improve your cholesterol level, and achieve and maintain a healthy weight.

When you are planning your meals, you should consider how to incorporate the GI into your food choices. The following are useful pointers:

  • Mixing high-GI foods with lower-GI alternatives will help to lower the overall GI of the meal. For example: High-GI food (baked potato) + low-GI food (baked beans) = medium-GI meal
  • Low-GI foods are not always healthy. For example, ice cream, nuts and chocolate all have a low to medium GI but are high in fat and calories. Such items should be eaten in small quantities.
  • High-GI foods, e.g. watermelon, can be a good source of nutrients, so they do not need to be avoided altogether just because they have a rapid and marked effect on your blood glucose levels.
  • Focus on the overall GI content of your meal to keep your blood glucose levels within a target range.
  • For a healthy, balanced approach to eating, include low-fat and low-sugar foods with a lower GI as a basis for meal and snacks

The diagram below demonstrates how low-, medium- and high-GI foods can affect blood glucose over time.

 

Table 1 illustrates the GI values of some common foods.

Table 1: Low, medium and high GI values

 

Low GI

Less than 55

Medium GI

55–70

High GI

Greater than 70

Breakfast cereals

All Bran

Sultana Bran

Muesli

Porridge oats

Instant porridge

Weetabix

Shredded Wheat

Special K

Coco Pops

Rice Krispies

Cornflakes

Cheerios

Bread, biscuits, cakes, confectionery

Rye bread

Pumpernickel bread

Granary or multigrain bread

Pitta bread

Wholemeal bread

Crumpet

Digestive biscuit

Rich Tea

Chocolate

Baguette

White bread

Bagel

Potatoes, rice, pasta

Sweet potatoes

Noodles

Pasta

New potatoes

Boiled potatoes

Couscous

Brown rice

Basmati rice

Crisps

Instant potatoes

Baked potatoes

Instant rice

Chips

Fruit and vegetables

Apples  

Grapefruit  

Grapes  

Kiwis  

Oranges  

Peaches  

Pears  

Carrots  

Peas

Apricots  

Mangoes  

Pineapples  

Raisins  

Sultanas  

Melons

Watermelon  

Turnip  

Parsnips

Beans and pulses

Baked beans

Butter beans

Black beans

Kidney beans  

Chick peas  

Lentils  

Nuts

 

Broad beans

Milk and dairy

Milk

Custard

Yoghurt

Ice cream

 

 

The key is to use the GI in the context of balanced eating. A healthy way to use the GI principles is to incorporate a range of lower GI carbohydrates that are also low in fat and calories into your meals.

Useful resources

The following is a source of more useful information about the GI and how it can benefit your diet: 

http://www.the-gi-diet.org/glycemicindexchart/ 

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