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Glycaemic Index and Glycaemic Load

Glycaemic Index and Glycaemic Load

Glycaemic Index

The glycaemic index is essentially a numeric value assigned to a wide range of carbohydrate sources to indicate their ability to influence blood glucose level after being ingested. Carbohydrates are scored on a scale of 0-100 with 100 causing the greatest spike in blood glucose level in the shortest amount of time (7.8mmol/L under 15-30 minutes post-prandial) after a meal.

Spikes in blood glucose concentrations after a meal are normally mitigated by insulin which is secreted by the pancreas. In normal individuals, the pancreas secretes adequate insulin to remove the excess blood glucose from the blood stream, returning to normal levels. In diabetics however, they either have insufficient insulin (type 1 diabetes) or their insulin receptors are not responsive (insulin resistance). In their case, constant levels of raised blood glucose which goes uncorrected is the cause of many complications such as neuropathy, retinopathy and cataracts as well as heart diseases. Therefore the GI comes in handy to keep them informed about the various types of carbohydrates they should stick to and avoid.

In normal individuals, the sudden spike and dip in blood glucose after eating refined carbohydrates can result in a ‘food coma’ as the carbohydrate transits the gut relatively quickly. This could also lead to a feeling of hunger shortly after consuming our food, potentially making you eat more than you have to, leading to weight gain in the long run.

Table 1 gives an example of foods and their associated GI ranges.

Table 1. Foods and their associated GIs (Diabetic Society of Singapore, 2011)

Glycaemic Index

Food sources

Low (≤55)

Rice and alternatives

  • Rolled oats
  • Multi grain bread
  • Spaghetti
  • Semolina

Vegetables

  • Sweet Corn

Dairy Products

  • Yoghurt
  • Milk

Medium (56-69)

Rice and alternatives

  • Natural muesli
  • Wholemeal bread
  • Dried rice noodles
  • Basmati rice, wild rice, brown rice

Vegetables

  • Sweet potato

High (≥70)

Rice and alternatives

  • Cereals
  • White bread
  • English muffin
  • Jasmine rice
  • Tapioca

Vegetables

  • Most potatoes

 

Typically, we would want to choose carbohydrate sources low in GI because these foods usually come with the vitamins, minerals and fibre which we require for general health and weight management.

Factors affecting GI

Unknown to many, the GI of a carbohydrate can be influenced by a multitude of factors such as: 

  1. Increasing the amount of  fibre present by adding green, leafy vegetables to our meals can decrease GI
  2. Increasing the amount of protein or fat present in our foods by choosing dishes with lean meat or adding legumes can decrease GI 
  3. The amount of amylose present in the starch - a lower amylose content typically results in a lower GI (potatoes & corn starch) 
  4. Acidity of food - the addition of an acid such as balsamic vinegar to your carbohydrate source may lower its GI 
  5. Degree of cooking - undercooked pasta/rice tends to have a lower GI as compared to those cooked to a greater degree

 

With these in mind, you now have a good idea what to do when eating out and faced with endless healthy carbohydrate options!

Glycaemic load

Another measure to take into consideration when choosing your food carbohydrate source is glycaemic load (GL),which is derived by the equation below:

GI tells us how quick the particular carbohydrate raises our blood glucose whereas GL indicates how elevated your blood glucose will be after food consumption, which is primarily determined by the amount of carbohydrate ingested. For example, a serving of Gatorade (250mL when diluted)that contains 14g of carbohydrates has a GI of 89 (very high) but has a GL of only 13 (medium) (Refer to table 2).

Table 2. Glycaemic load tiers and corresponding values

Glycaemic Load

Low

≤10

Medium

10.1-19.9

High

≥20

 

GL thus gives you a fuller, more accurate picture of the effects which sugars from food can have on your blood stream.

Why should I incorporate low GI foods into my diet?

Research has shown that consumption of low GI foods have an association with weight management and improvement of general health. Therefore it may be prudent to gradually increase our intake of whole grains to better able experience the health effects of low GI carbohydrates as well as manipulating the other factors to lower the GI of your meal.

These changes do not have to be a complete overhaul of your diet because that would not be sustainable. Sustainability is the key to a successful diet! Here are a few tricks you can use to lower the GI of your meal:

  • Choose brown/ basmati/wild rice over white rice, or substitute a portion of white rice for aforementioned variety
  • Add some green, leafy vegetables and/ or lean protein such as meat, chicken or fish into your meal if you’re having white rice/beehoon to lower the GI of your meal
  • Choose wholemeal or multigrain bread over white breads.
  • Choose oats topped with moderate amount of fruit over sugar laden packaged cereals

 

Follow these guidelines and you’ll be on your way to a trimmer, healthier you!

Fitness 101
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Glycaemic Index and Glycaemic Load