What is the glycemic index?
The glycemic index (GI) is a number given to carbohydrate containing foods which ranks them on a scale from 1 to 100 according to their effect on blood sugar levels compared to the standard of pure sugar (glucose), which has the greatest effect on blood sugar = a GI of 100.
Carbohydrate containing foods, which include grains, starchy vegetables, fruit and dairy products are placed into one of 3 GI categories: Low, Moderate and High
Low GI foods have a score of less than or equal to 55. These foods produce only small fluctuations in blood sugar and insulin levels, which assist to keep energy levels balanced and decrease hunger by keeping you feeling full for longer. Consuming a daily diet made up of a significant amount of low GI foods has the potential to help reduce the risk of heart disease and diabetes, along with improved blood cholesterol levels and weight management.
Moderate GI foods have a score of 56 to 69
High GI foods have a score of 70 and above. In the daily diet high GI foods should be consumed in moderation, but while training and racing high GI foods are the focus.
How do GI foods fit into athletics?
Different GI foods can be used at specific times throughout training/racing to enhance performance and aid in recovery. Therefore the GI score can be used to choose the most appropriate foods for pre, during and post training/racing.
In general low GI foods are best consumed pre-training/racing (given that you have at least 2 hours digestion time) since they result in consistent maintenance of blood sugar levels, which spares muscle glycogen utilization during prolonged exercise, leading to the potential for improved performance.
Just prior to the start of an event, a high GI food snack can be consumed within 10-20mins of the start. This will work to provide a boost of energy and dampen hunger without the subsequent transient hypoglycemia that can result if taken > 30 mins from start time.
High GI foods are also perfect for during and immediately after training/racing. During activity high GI foods provide quick and easy energy for working muscles, and post activity they provide immediate replenishment of glycogen stores.
However, it just so happens that many of the foods we consume have a moderate GI. Moderate GI foods can be used in combination with low GI foods for pre-training/racing snacks and meals, which can help to replenish liver glycogen stores used up in the overnight fast. And Moderate GI foods can be used in combination with high GI foods during and post-training/racing to assist in sustaining energy levels during, and providing for greater nutrient density for post-training/racing.
Following are GI tables. The 1st lists common pre-training/racing breakfast foods listed from lowest to highest GI (since our focus is low GI foods for pre-training/racing), and the 2nd lists common during training/racing foods from highest to lowest GI (since our focus is high GI foods for during training/racing).
| Food | GI |
| Common Breakfast Foods | |
| Dried apricots | 32 |
| Orange | 30-48 |
| White/wheat spaghetti | 40-60 |
| Multigrain English muffin | 45 |
| Orange juice | 45-55 |
| Pasta | 45-60 |
| Up & Go beverage cocoa/malt flavor | 46 |
| Banana, ripe | 47-62 |
| Skim milk | 48 |
| Brown rice (slow cooking) | 48 |
| Apple muffin made w/ rolled oats | 48 |
| Muffin | 48-65 |
| Porridge made from rolled oats | 49 |
| Muesli breakfast bar | 50 |
| Raisins | 54-64 |
| Vogel’s honey & oats bread | 55 |
| Alpen original muesli | 55 |
| Rolled oats | 59 |
| Whole grain bread | 60 |
| Crunchy muesli –apricot bar | 61 |
| Scottish oats | 63 |
| Yoghurt | </= 64 |
| Weetabix /Vita-Brits | 69 |
| During Training/Racing Foods | GI |
| Glucose 50g | 100 |
| Clif bar- cookies & cream | 100 |
| Gatorade | 89-100 |
| Dextrose 50g | 96 |
| Baked potato w/out skin | 87-98 |
| Pretzels – traditional | 84 |
| Jelly beans | 76-80 |
| Honey –commercial | 62 |
| Bread with jam | 62 |
| Creamed rice | 59 |
| Chewy granola bar | 58 |
| Clif bar – chocolate brownie | 57 |
| Coca Cola | 53-63 |
| Power bar- performance choc | 53 |
| Fructose 50g | 23 |
How do I know which foods are low GI for my daily diet and high GI for training and recovery?
Vegetables: Low GI = non-starchy vegetables, legumes, peas and beans.
High GI = starchy vegetables: sweet corn, potato, sweet potato, taro & yams.
Fruits: Low GI = Temperate climate fruits: apples, pears, citrus (oranges, grapefruit) and stone fruits (peaches, plums, apricots).
High GI = Tropical fruits: pineapple, paw paw, papaya, rock melon and watermelon
Grains: Low GI = buckwheat, quinoa, brown & basmati rice
Breads: Low = those made from chickpea (besan) or legume based flours and those made with buckwheat, rice bran and psyllium husks. Also sour dough breads and those made with stone ground flour.
High GI = most others: white, wholemeal, and corn products (tortillas)
Cereals: Low GI = wholegrain, high fiber, low sugar cereals. Look for cereals that are based on oats, barley and bran.
High GI = puffed cereals, and those low in fiber and high in sugar
Pasta: Best for low GI = buckwheat (soba) noodles, cellophane noodles (lungkow bean thread) and green bean vermicelli (mung bean flour noodles). Low to Moderate GI = most other spaghetti and pastas
High GI grains: millet, crackers, biscuits, rolls, most breads and cakes, and snack foods such as corn and potato chips, rice cakes, corn thins and rice crackers.
Also Low GI = Nuts (healthy fats) and Low fat diary products
Note: Consuming low GI foods is a healthy way of eating, however; this does not mean that you have to cut out all moderate to high GI foods from your daily diet. All of the various fruits and vegetables have different nutrients and health benefitting compounds, so it is important to consume a wide variety of foods from each food group every day. For athletics concentrating on consuming low GI foods during the daily routine plus pre-training/racing meals, and then focusing on high GI foods during training/racing and in recovery is the key to using GI for enhanced performance.
