The Glycaemic Index (GI)

Each time we consume sugary or starchy food or drink , blood glucose levels in our body rises. Some of these foods are quickly digested and cause quick and sharp rises in the blood sugar levels - they are called high-GI foods and drinks. Low-GI foods and drinks, which are more slowly digested, make the blood glucose rise more slowly. These are sometimes called ‘slow-release’ carbohydrates.

Foods with high GI are not necessarily bad foods. For example, crisps have a medium GI but a baked potato has a high GI. Despite this, a baked potato is better for health than crisps, which are higher in fat and salt. Also, all lower GI foods are not necessarily healthy - chocolate and ice cream have a low-to-medium GI rating.

The GI value of a food is tested on the food when eaten on its own, and there are published lists of high, medium and low GI foods. However, it is not helpful to use the GI values in isolation, as we generally eat a combination of foods.

Low GI Foods (55 or Less)

  • Peanuts (14)

  • Cherries (22)

  • Red lentils (26)

  • Milk (27-32)

  • Dried apricots (31)

  • Wholemeal spaghetti (37

  • Apple juice (40)

  • Porridge with water (42)

  • Peas (48)

  • Crisps (54)

Medium GI Foods (56 to 69)

  • Muesli (56)

  • Boiled potatoes (56)

  • Pitta bread (57)

  • Basmati rice (58)

  • Digestive biscuit (59)

  • Ice cream (61)

  • Coca-cola (63)

  • Fresh Pineapple (66)

  • Croissant (67)

  • Mars bar (68)

  • Wholemeal bread (69)

High GI Foods (70 or more)

  • Mashed potato (70)

  • White bread (70)

  • Watermelon (72)

  • Bran flakes (74)

  • Chips (75)

  • Coco pops (77)

  • Jelly beans (80)

  • Rice cakes (82)

  • Jacket potato (85)

  • Baguette (95)

  • White rice (98)

  • Dates (100)

Weight management & G.I.

GI is a well-known weight management tool, however, it can be restrictive as it measures foods per 50 g of carbohydrate provided and not the portion size, so foods like carrots are included in the high-GI list along with other important fruit and vegetables.

Glycaemic load (G.L)

This is a sum which takes into account the GI of a food and the available carbohydrate content in a serving of that food. Like GI, the higher the G.L, the faster the expected rise in blood sugar.

For example, carrots have a high GI but a low G.L. This is because GI is based on the rise caused by consuming 50 g of carbohydrate from any food. To get 50 g of carbohydrate from carrots, around 700 g of carrots (about five) whole carrots would need to be eaten. As the portion of carrots eaten is typically much smaller - at 60 g rather than 700 g - carrots have a low G.L.

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