Glycaemic index: Dr Joe Kosterich

Video transcript

We hear a lot these days about the glycaemic index and most people know it’s something to do with food but like a lot of medical and nutritional terms can be a little bit confusing as to what it really means to me.
Glycaemic index in most simple terms is a measure of how quickly any sort of food gets absorbed into your body. Now, the higher the glycaemic index the more quickly the food is absorbed into your blood stream, that means the faster the sugars reach your blood stream. A lower glycaemic index means the food gets absorbed more slowly and it means your body has more time to deal with it.
Once upon a time this didn’t really matter because virtually none of our food was processed. Our ancestors ate what they gathered or could catch and even 50 years ago we didn’t eat a lot of foods that came out of manufacturing plants. Today things are a little bit different.
The significance of all this is our bodies are designed to process foods at a certain rate and if somebody or something has done a lot of the work for us then that means the body gets hold of the sugars more quickly. It then has to respond so I’ll tell you what happens. Say you eat something; it’s inside the stomach and intestine, it starts to get broken down. As it gets broken down it gets absorbed into your blood stream. As the sugar level in your blood stream rises, the body releases insulin from the pancreas gland. Now the role of that insulin is to make sure that sugar reaches the body’s cells. Glucose in the blood stream is a bit like petrol in a car, every single cell in your body needs glucose to function. Obviously it needs oxygen and other things too but glucose is the body’s petrol so it needs it. But the body wants to have your blood glucose within a certain range and the role of insulin is to drop it down if it gets to high so after you eat you get a bit of a spike in your blood glucose level as you’d expect, then you get a bit of a spike in your insulin level and then down comes the sugar level and down comes the insulin level and everything should revert to normal in about 2 hours.
If the food gets absorbed more quickly it puts pressure on the system to put out more insulin and this eventually, over many years, leads to what we call insulin resistance because to be honest the body’s cells get a little sick of being flogged by all this insulin. Why does that happen? Because your body is trying desperately to keep your sugars in a normal range. So, let’s think of a practical example. If I eat an apple the body has to break down that apple, I will have to chew it, then swallow it and then more will get digested in the stomach, the stomach will release some acid, that will break down more of the apple and eventually some of it will get absorbed into my body. Now some of the apple won’t get absorbed and that’s the fibre part and we know about that.
If I drink a glass of apple juice, I don’t have to chew it, it’s much easier to swallow, the stomach doesn’t have to work as hard so it will get absorbed much more quickly. What does that mean? It means that my sugar level will rise faster. A glass of apple juice usually gets made from about four apples. It’s fairly unlikely I would sit and eat four apples all at once and if I did I’d be fairly full and probably wouldn’t want to eat for a while. But I can drink a glass of apple juice and it’s not going to fill me up. So a glass of apple juice will have a much higher glycaemic index than an apple. There are lots of other examples and there’s plenty of other books and information you can find out about different foods and glycaemic index. Don’t get too carried away with it and don’t make life harder than it needs to be but be aware that the more work that has been done to any sort of food before it enters you, generally speaking, the faster that food is going to be absorbed. Different fruits have different glycaemic indexes, even different types of rice can have different GIs. Be aware of these things but it’s not a university research project, don’t get carried away.
So what are the key messages? Be aware of the glycaemic index and this is not just for people with diabetes, it’s good for everybody and just think about it in simple terms. The more processed or altered any foods have been the more quickly those foods will be absorbed into your body and the higher the glycaemic index. Can you have a little bit of these foods? Of course you can. Should that be the mainstay of your diet? Probably not. Follow the basic principles. Be aware of the glycaemic index and mainly focus on those foods that have a lower, rather than a higher, GI.