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Health news - Low GI foods good for your health

25 May 2005 - written by Bupa's Health information team

Adding just one low GI food item to each meal may have a positive effect on your blood sugar levels, according to a study published in the February 2005 edition of the British Journal of Nutrition.1

How was the study carried out?

The researchers recruited nine healthy women and measured their blood sugar levels at the start of the study.1

The women were given advice and written information about key foods with a low glycaemic index (GI). They were asked to incorporate one low GI key food into each meal, while keeping their overall intakes of energy, proteins, fats and carbohydrates the same as normal.1

After a minimum of seven days, the women had their blood sugar levels measured again.1

What did the study show?

The researchers found that after one week on a lower GI diet, eight of the nine women had lower blood sugar levels.1

What is the glycaemic index?

The glycaemic index (GI) is a system that tells you how fast a particular food triggers a rise in your blood sugar levels. A food with a high GI will cause a fast rise in blood sugar while a food with a low GI will bring about a slower rise. The type of carbohydrate in food influences blood sugar levels.2

What does the blood sugar do?

When you eat, sugar (glucose) from the food goes into the blood from the intestines.3

When glucose reaches the various body tissues, such as the muscle cells, it is used for energy. The level of glucose in the blood is automatically regulated so that it doesn't go too high or too low. But it is higher after meals and usually lowest first thing in the morning before you have eaten.1,3

Why are lower blood sugar levels important?

Although it is not very well understood, if someone has high blood sugar, in the long term it can damage small blood vessels. It particularly affects the small blood vessels in the heart, brain, kidneys and eyes, so it increases the risk of diseases in these parts of the body. Keeping blood sugar levels stable can help to decrease the risk of this happening.4

Keeping blood sugar levels steady may also help to prevent or reduce your risk of developing diabetes.

How can eating low GI foods help to control blood sugar levels?

When you eat low GI foods, your body takes longer to absorb the carbohydrate. This helps keep your blood sugar levels steadier between meals.2

What are the other benefits of eating GI foods?

Lower GI diets have been associated with higher levels of 'good' cholesterol and excess weight loss. Eating low GI foods may make you feel fuller for longer after eating, which may help you avoid snacking between meals and eat less overall.2,5

How is the GI for a food worked out?

Glucose (sugar) has been given a GI ranking of 100.2 This is used as the standard reference and other foods are measured against this. The GI values are often categorised into three categories:5

  • low: GI < 36
  • medium: GI 36-50
  • high: GI 51-100

Which foods have a low GI?

Examples of foods that have a low GI include:2,5

  • some fruit (eg apples, oranges, pears)
  • beans, peas, pulses and lentils
  • porridge
  • bran cereals
  • custard (with no added sugar)
  • peanuts

Which foods have a high GI?

Examples of foods that have a high GI include:2,5

  • bread (white and wholemeal)
  • rice (brown and white)
  • cornflakes
  • baked and mashed potatoes

Is it easy to work out the GI value of my meals?

If you use a GI chart, it will give you the GI value of individual foods. But your meal will usually consist of a mixture of foods and the fats and protein in the food tend to slow down the absorption of carbohydrate. The GI may also be affected by cooking, processing, ripeness and variety. It is difficult to interpret the GI of your diet, but if you include some low GI foods with each meal, this will help to lower your blood sugar levels overall.2,5

For the GI values and carbohydrate content of a range of common foods, please see the Bupa article:
GI and carbohydrate table

Should I only eat low GI foods?

No. If you only ate low GI foods, your diet would be unbalanced. Some foods have a low GI but are high in fat and high in salt, which is not healthy. You need to think about the overall balance of your meals, which should include a combination of starchy foods, fat and protein. They should be low in saturated fat, sugar and salt.2,5

Sometimes it's necessary to eat high GI foods. For example, after exercise, when muscle stores of sugar need to be quickly restored, a high GI food is a good choice.5

To maximise the benefit of GI you could include a low GI food with each meal or snack.1,2,5

For more information on healthy eating, please see the Bupa factsheet:
Healthy eating

Bupa information

Further information

References

  1. Brynes AE, Adamson J, Dornhurst A et al. The beneficial effect of a diet with low glycaemic index on 24h glucose profiles in healthy young people as assessed by continuous glucose monitoring. Br J Nutr 2005; 93: 179-182.
  2. Diabetes UK, Glycaemic index.
    www.diabetes.org.uk
  3. Patient UK, Type 2 diabetes.
    www.patient.co.uk
  4. The British Medical Association (BMA). Diabetes mellitus.
    www.bma.org.uk
  5. West Suffolk Diabetes Service. Living with diabetes: the glycaemic index.
    www.diabetesuffolk.com

All websites accessed on 20 May 2005

 

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