Glycaemic Index

Following training and competition, an athlete's glycogen stores are depleted. In order to replenish them the athlete needs to consider the speed at which carbohydrate is converted into blood glucose and transported to the muscles. The rapid replenishment of glycogen stores is important for the track athlete who has a number of races in a meeting. The rise in blood glucose levels is indicated by foods Glycaemic Index (GI) and the faster and higher the blood glucose rises the higher the GI. Studies have shown that consuming high GI carbohydrates (approximately 1grm per kg body) within 2 hours after exercise speeds up the replenishment of glycogen stores and therefore speeds up recovery time.

The six elements to determine the GI of a food

1. Does it contain carbohydrate?

Pure protein foods such as meat, fish, poultry and eggs, and pure fats such as oils, butter and margarine, contain no carbohydrate. As a result, the effect they have on glucose production is negligible. These foods are therefore low Gl.

2. How much starch does it contain, and in what form?

The easiest ingredient for our body to convert into glucose is starch. When foods are raw, this starch is generally found in hard, compact particles that the body finds hard to break down. However, if something disturbs these starch particles (e.g. milling into flour), the body finds it much easier to digest them and they turn into glucose faster.

3. How much fibre does it contain?

Fibre slows the time it takes the body to break down a food. This is one reason why beans and pulses (which are wrapped in a fibrous shell) have such a low Gl.

4. What kind of sugar does it contain?

There are four main types of sugar, and they raise blood sugar levels at different rates. Foods with a high concentration of glucose (such as sports drinks) need no conversion, so they raise blood sugar rapidly. Fructose (the sugar in fruit), however, converts slowly; as does lactose which is the main sugar in dairy products. This gives the majority of foods containing either fructose or lactose a low Gl. The fourth sugar, sucrose, has a medium Gl.

5. Does it contain fat?

As well as having no effect on glucose itself, fat slows the speed at which food leaves the stomach and reaches the liver, slowing glucose production. This is the reason why potato crisps have a lower Gl than most other types of potato.

6. How acidic it?

Foods can contain acid ingredients - citrus fruits like oranges or lemons are a good example of this. The tang they create on your tongue comes from the citric acid they contain. Other acidic ingredients include lactic acid in milk products, and added ingredients, such as vinegars, in pickled products, just like fat, acidity slows a food's progress through the system, and therefore slows the rate at which it converts into glucose.

High Glycaemic Index (>85)

Breads, breakfast cereals and cerealsBaguettes         Crunchy nut cornflakes      Puffed wheat        White bread

Bagels   Dark rye bread     Rice crackers        White rice

Bread stuffing      Gluten-free bread                Rice krispies         Wholemeal bread

Coco pops            Gluten-free maize Pasta    Shredded wheat 

Corn pops             Gluten-free rice    Sultana bran Tapioca        

Crackers                Jasmine white rice                              

Vegetables and pulsesBroad beans               Mashed potato     Pumpkins

Jacket potatoes    Parsnips                Swede

FruitsDates           Tinned lychees    Watermelon

Snack foodsCorn cakes     Glucose tablets    Plain scones         Glucose-based drinks, e.g. sports drinks

Doughnuts            Honey    Popcorn Tofu desserts

French fries          Jelly beans           Pretzels Wafer biscuits

Fruit bars               Morning coffee biscuits      Rice cakes            Waffles

Moderate Glycaemic Index (>60)

Breads, breakfast cereals and cerealsArborio rice      Chapati  Gnocchi Pitta bread

Arrowroot biscuits                Couscous              Hamburger buns Rice noodles

Basmati rice         Croissants             Melba toast           Rye crispbreads

Brown rice             Crumpets              Pancakes              Wholemeal rye bread

Vegetables and pulsesBeetroot       Carrots   Potatoes, peeled and boiled

FruitsDried figs    Pineapple             Tinned fruit cocktail

Melon     Tinned apricots    Tinned peaches

Snack foodsBean soup      Ice cream              Oatmeal biscuits  Potato crisps

Digestive biscuits                Muesli bars           Pea soup               Raisins

Flans      Muffins  Plain cake            

Low Glycaemic Index (<60)

Breads, breakfast cereals and cerealsAll-bran             Grain breads        Pumpernickel       Soya and linseed bread

Barley    Oat bran                Rice noodles        Spelt wheat bread

Buckwheat            Oats        Seeded breads    Toasted muesli

Bulgur wheat        Pasta of all types Sourdough rye     Turkish wholewheat bread

Vegetables and pulsesBaked beans              Chickpeas             Lentils    Soya beans

Black-eye beans  Haricot beans       Lima beans          Sweet potatoes

Butter beans         Kidney beans       Peas       Sweetcorn

FruitsApples         Dried apricots       Mangoes               Plums

Bananas                Grapefruit and its juice       Oranges                Prunes

Cherries                Grapes   Peaches                Strawberries

Dried apples         Kiwi fruit                Pears    

Snack foodsApple juice     Hot chocolate       Low-fat yogurt      Skimmed milk

Cashew nuts        Grainy fruit loaf    Malted milk           Tomato soup

Corn chips            Low-fat chocolate mousse                Minestrone soup  Tortillas (corn and wheat)

Cranberry juice    Low-fat custard    Peanuts