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Fast facts: All about low GI

You might have heard that eating low GI food is a good idea. But what foods are actually low GI and what does it mean when food has a low GI? We asked registered dietician Chantelle van der Merwe to tell us all about low GI.

What is GI (Glycemic Index)

GI refers to the ability of a particular food to raise blood glucose levels. It is a very useful tool to use to help optimize blood glucose regulation because it provides a guide for which foods will have a slow and steady affect on blood glucose levels.

The GI scale ranks carbohydrate rich foods on a scale of 1-100 according to their actual effect on blood glucose levels.

Chantelle van der Merwe, Dietitian

Internationally, pure glucose is ranked at 100 since it causes the greatest and most rapid rise in blood glucose levels. All other foods are ranked on the GI list in comparison with glucose. Low GI foods will raise blood glucose levels a lot slower when compared to glucose or other high GI foods.

Why to choose low GI over high GI foods

All carbohydrates are not created equal. This means that the same amount of carbohydrates
consumed from different foods will cause different glycaemic responses or increase blood
glucose at different rates.

Lower GI foods promote a slow, steady increase in blood glucose levels. This can contribute to more stable blood glucose control.

Chantelle van der Merwe, Dietitian


Some of the benefits of well-regulated, stable blood glucose levels include:

  • Having more sustained energy levels throughout the day resulting in better
    concentration levels and performance.
  • Enhanced mood regulation because you don’t feel so sluggish or irritable.
  • Feeling more satisfied throughout the day, which contributes to better appetite control.
  • Reduced insulin resistance which can contribute to healthier weight management.

Examples of low GI foods include:

  • Rolled oats
  • Seeded bread
  • Legumes (beans, peas, lentils, chickpeas)
  • Corn on the cob
  • Sweet potato
  • Citrus fruits and
  • Low carbohydrate vegetables (green beans, cauliflower, spinach, lettuce, kale, cucumber, brussels sprouts, tomatoes, cabbage, broccoli, asparagus, mushrooms)

Examples of high GI foods include:

  • Cereals
  • Regular brown, white and ordinary wholewheat bread (unless it states “low GI”)
  • Potatoes
  • Mieliemeal porridge
  • Watermelon

Eating more low GI foods can reduce the amount of insulin your body needs to produce compared to when high GI foods are consumed. High GI foods raise blood sugar levels more rapidly. Remember, insulin is the hormone our body produces in response to increasing blood glucose levels. Insulin removes glucose from the blood and stores it in our liver and muscles.

How insulin works in the body

Insulin and glucose levels work together. Rapid spikes in blood glucose levels require large amounts of insulin production to keep up with rising blood glucose levels. Large amounts of insulin release can result in blood glucose levels plummeting which triggers a crash in energy levels and exacerbates the feeling of being hungry. If we “feed” this hunger with more high GI foods, the vicious cycle continues resulting in a non-stop roller coaster ride of less stable blood sugar levels.

Energy levels spike as glucose levels rise, followed by a crash in energy levels as large amounts of insulin is produced to drop glucose levels quickly. Depleted energy levels increase cravings for high GI foods, a natural response by the body to try and get quick energy.

For a regularly updated GI list of South African foods visit The Glycemic
Index Foundation of SA website.

Benefits of a low GI diet for people with diabetes

Controlled blood glucose levels mean you don’t only minimize risk for high blood glucose
levels (hyperglycemia) but you also reduce the risk of blood sugar levels falling too low
(hypoglycemia).

The quantity and quality of carbohydrates needs to be considered. Low GI foods still contain carbohydrates and should still be appropriately portioned. As a general guideline, limit carbohydrate containing food portions to about a cup size (250ml) portion or no more than two slices of bread or ½ cup muesli.

Always consult with a dietician to assist you with appropriate portions and additional
personalized guidelines to optimize your individual blood glucose control.

The GI is a guideline. Remember: our body’s response to foods is quite unique and complex.

Chantelle van der Merwe Registered Dietitian

My top 5 principles to remember are:

  1. “Dress your carbs”.
    Try eating a protein and/ or fat containing food with carbohydrate containing foods. Fat and protein slow down the rate at which foods leave the stomach (digestion takes longer), thus absorption rate is slower and subsequently rate of glucose rise is slower. An example would be: a slice of low GI bread (carbohydrate) “dressed” with smashed avocado or peanut butter (as a fat source) or scrambled egg (as a protein).


2. More high fibre foods.
Specifically soluble fibre, another GI lowering component in food. Soluble fibre thickens the stomach contents and thereby slows the rate of movement of food from the stomach to the intestines for absorption of carbohydrates. Examples of foods with soluble fibre include:
– Oat bran
– Minimally processed oats
– Legumes (beans, peas, lentils, chickpeas)
– Citrus fruits and
– Deciduous fruits (such as apples, peaches, pears and plums) and berries.

3. Unprocessed foods.
The more processed the food, the easier it is for the body to digest, which subsequently raises the GI. Milling, liquidising, grinding, mashing and over cooking carbohydrates are ways of increasing the digestibility of food and its potential to raise blood glucose levels faster.
Unprocessed/minimally processed foods include:
– Vegetables
– Grains
– Legumes
– Fruits
– Nuts
– Meats
– Seafood
– Herbs and spices
– Garlic
– Eggs and
– Milk.
– Basically any whole foods that resemble how they’re found in nature.

4. Acidity.
Acids slow down the movement of food from the stomach to the intestines, thereby lowering the GI. For example, pickled beetroot has a lower GI than cooked beetroot, tart fruits such as citrus fruits have a lower GI than sweet fruits, and sourdough bread also has a lower GI. (Read about if sourdough bread is better for diabetes here!)

And lastly:
5.Speed of eating.
Research confirms that blood glucose levels rise slower when eating more slowly.

If you would like to get in touch with dietician Chantelle van der Merwe:

Instagram: @chantellevdm_diabeteshealth
Facebook: Chantelle van der Merwe Registered Dietitian
Website: www.essnutriments.co.za

What to read next?

10 Fast facts about heart disease: Did you know that diabetics are more at risk of developing heart disease? Here are the facts and what you can do about it.

Living the low carb life: When Vickie de Beer’s son Lucca was diagnosed with Type 1 diabetes, she started a journey that ended with her publishing an award-winning cookbook and lifestyle guide: The Low Carb Solution for Diabetics.

A simple way to eat low carb (LCHF): any people feel that low carb (LCHF) is the only way to eat, while others feel that it’s too expensive or that there hasn’t been enough research done. We asked community member Michael Marnewick to share his experience of a simple way to eat low carb.

Photos by TABHISHEK HAJARE and micheile dot com on Unsplash

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  1. […] a quarter of a plate of protein (chicken, fish, eggs, meat, legumes), a quarter of wholegrain, low GI carbohydrates (if you eat carbs) and half a plate of green, leafy […]

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Sweet Life is a registered NPO/PBO (220-984) with a single goal: to improve diabetes in South Africa. We are funded by sponsorships and donations from aligned companies and organisations who believe in our work. We only share information that we believe benefits our community. While some of this information is linked to specific brands, it is not an official endorsement of that brand. We believe in empowering people with diabetes to make the best decisions they can, to live a healthy, happy life with diabetes.