How to use the glycaemic index


The glycaemic index (GI) is a useful a tool for controlling blood-sugar levels in diabetics, people with hypoglycaemia as well as in sportsmen and women.

Here's what it means in practice:

Tips to lower the GI of meals

To lower the GI of a meal, you can do the following:

  • Add vegetables to a starchy meal to reduce the GI, for example eat roasted vegetables with potato to lower the high GI of the potato.
  • By cooking starches and cooling them down, you can lower their GIs, for example cold maize meal porridge has a lower GI than hot porridge, and cold potato salad has a lower GI than hot boiled potatoes.
  • Select foods that are less ripe, for example a firm, yellow banana has a lower GI than a soft, ripe, mushy banana (75 vs 90).
  • Add organic acids like vinegar to a high starch meal, for example serve salad with a bit of oil and vinegar to lower the GI of the starch in the meal.
  • Use what we call the "second-meal effect" to lower the GI of your diet. By eating foods with a low GI at breakfast (All Bran cereal, milk and orange juice) the effect carries over to lunch (bread, lettuce, ham, apple).
  • Add legumes to meals to lower the GI. Dry beans, peas and lentils, tinned beans, bean soup, and textured vegetable protein (Toppers) will all lower the GI of a meal (e.g. eat baked beans with toast, three-bean salad with rice, or add a tin of butter beans or Toppers to stews served with mashed potato).

Replacement foods

Here's a list of foods that can be substituted for high-GI foods to lower blood-glucose and insulin levels:

Brown and white bread: replace with low-GI bread (a great variety is available on South African shop shelves).

Processed breakfast cereals: replace with high-fibre bran, maize meal which has been cooked, cooled and heated up again, oat porridge or Maltabella.

Plain biscuits and crackers: replace with biscuits or rusks that contain dried fruit, whole grains, bran and nuts (start baking again!).

Tropical fruits: replace with fruits that grow in a cool climate like apples, peaches, pears and citrus.

Potatoes: replace with pasta, legumes, samp, long-grain or Basmati rice.

White rice: replace with cooked, crushed wheat.

Cooked maize meal (mielie pap): replace with cooked, cooled and reheated maize-meal porridge.

Tips for sportsmen and women

While you're training, you need to eat foods with a low GI to give you sustained energy release, e.g. dried fruit, fruits such as apples, pears, bananas that aren't too ripe, oats, pasta, low-GI bread etc.

However, when you need an instant, short, sharp burst of energy or when you're feeling really exhausted after training, select foods with a high GI to restore your blood-glucose levels, e.g. jelly beans, Lucozade, mashed potato, refined cereals etc.

Tip for slimmers

Remember that you can combine foods with different GIs and that this is particularly useful if you're trying to lose weight and don’t want those horrid hunger pangs and dizzy spells caused by low blood-sugar levels.

- (Dr IV van Heerden, DietDoc, updated October 2008)

Any questions? Ask DietDoc

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