Carb Counting Series: The Glycaemic Index

The abbreviation GI is not an uncommon term to come across, particularly among the nutrition-conscious. While diet and nutrition experts will often tout “low GI foods” as superior, what is low GI anyway? Is high GI the devil? Here’s what you need to know about the glycaemic index and living with type 1 diabetes.

The Glycaemic Index

The glycaemic index (commonly abbreviated to GI) is a ranking of how quickly food and drink can raise your blood glucose (BG) levels.¹ Low GI foods are those with a rating of 55 or under,¹ while high GI foods are those closer to 100. The lower the GI rating, the slower the glucose from your food is absorbed after being digested.¹ This also relates to the “speed” of carbs contained within these foods and drinks. Faster-acting carbs are rapidly absorbed while slow-acting carbs take longer to make their way to your bloodstream.

There are three general vicinities on the GI scale:

• High GI. These are foods and drinks that can cause your BG levels to rise rapidly as they contain fast-acting carbs. Due to this, high GI foods and drinks are useful for the moments you find yourself in hypoglycaemia.² These tasty snacks may be found in your hypo management kit, such as glucose tablets or beverages. Other examples of fast-acting carbs are full-sugar soft drinks and sweets.
• Medium GI. These foods and drinks fall in the middle of the GI range, causing a moderate rate of increase to your BG. These types of carbs can include bread, pasta, potatoes and yams, and couscous. Such foods and drinks also play a role in helping you manage hypos once you’ve had your high GI carb.²
• Low GI. Not to be mistaken for laziness, these carbs are slowly digested and absorbed by the gut to our great benefit. Low GI foods include beans, lentils, pearl barley, and some vegetables such as pumpkin and parsnips. Unless you’re gulping down huge amounts of low GI carbs, sometimes these foods and drinks don’t need to be matched with as much insulin.¹

Though it can feel overwhelming, having an understanding of the glycaemic index can help you manage your type 1 diabetes.¹ Your diabetes healthcare team can give you some further guidance on how certain carbs affect your unique body. Remember, not all carbs affect people the same way, even those living with type 1 diabetes.³ Whenever trying a new food, you may want to monitor your BG levels closely to see how they react.

Other Considerations As You Harness The Glycaemic Index To Your Advantage

The glycaemic index of an individual food or drink can be a useful indicator of which pace your carbs are moving at. However, it’s not the full picture. Remember that:¹

• Cooking methods can alter GI.
• The ripeness of fruit and some vegetables can also affect the GI.
• The amount of total carbohydrates in your meal or snack has more impact on your BG than just the GI number.
• Fat, protein, and fibre will slow the pace of any carbs in the dish by lowering the GI.
• The glycaemic index applies to food containing 50g of carbs. However, in reality, this may not be the exact amount in your meal.

Final Thoughts

It may be tempting to focus solely on the glycaemic index of your foods and drinks as you optimise your BG management. However, remember that it’s important to have a balanced diet. You may also want to consider using technology such as insulin pump therapy with continuous glucose monitoring to support your BG management. Features such as automated basal rate delivery and correction doses can make it easier to manage foods of different GI. If you’re stuck on how to formulate a healthy, balanced meal for yourself, talk to your diabetes healthcare team.

References

1. Diabetes UK. Glycaemic Index and Diabetes. https://www.diabetes.org.uk/. 2021. Available at: https://www.diabetes.org.uk/guide-to-diabetes/enjoy-food/carbohydrates-and-diabetes/glycaemic-index-and-diabetes. (Accessed July 2022).
2. Fumanelli J, Franceschi R, Bonani M, Orrasch M, Cauvin V. Treatment of hypoglycemia during prolonged physical activity in adolescents with type 1 diabetes mellitus. Acta Biomed. 2020;91(4):e2020103.
3. Diabetes UK. Why Understanding Carbs (and How to Count Them) Matters. https://www.diabetes.org.uk/. 2019. Available at: https://www.diabetes.org.uk/guide-to-diabetes/enjoy-food/carbohydrates-and-diabetes/nuts-and-bolts-of-carb-counting/learn-about-carb-counting/the-basics. (Accessed July 2022).