Podcast Episode 73 Transcript – Should We Care About Glycaemic Index?

Aidan:

Hello, and welcome to episode 73 of the Ideal Nutrition Podcast. My name is Aidan Muir and I’m here with my cohost Leah Higl. Today, we’re going to be talking about the glycemic index, what it is and whether we should care about it. We’re going to start off by going to what it is. Basically, it is a measure of how quickly and how much blood glucose levels raise in response to a certain amount of carbohydrate-rich food.

Low-GI foods are typically less than 55 on this scale of up to 100, and high-GI foods are above 70. For context, it’s a system based on glucose being at 100, although there is a few other systems of scaling it, but typically glucose is 100 and everything else is compared to that. Yeah, just measuring how much glucose levels raise.

Leah:

Why was it generally designed? It was designed, basically, to identify how much different foods raise blood glucose levels by. But this is going to be particularly relevant for people with diabetes, so people that have issues with managing their blood glucose levels. But it may also be linked to things like PCOS, in terms of it might be something you want to be mindful of in other conditions, but mostly relevant to things like diabetes. It does have links with improving acne in terms of going for lower-GI foods, which I think is always an interesting one to talk about. But at the end of the day, when we’re thinking of blood glucose levels, we’re mainly thinking about diabetes.

Aidan:

Yeah, the acne one’s interesting because it obviously doubles up with PCOS as well.

Aidan:

[inaudible 00:01:51] play a role there as well. The acne thing, I’ve probably spoken about this before on the podcast, but it’s one of those things where it’s like going lower GI, on average, seems to improve acne, but what happens if you go lower GI and you still have acne? That’s a very common outcome that I see a lot of people go through.

It’s like this is just one factor in acne as well. So, it’s like, on average improves it, but that doesn’t mean it’s the solution in every case.

Leah:

No, 100 percent. There’s a lot of different factors at play with acne.

Aidan:

Yeah. The first one, the most interesting one I think, to me, is whether it affects body composition. The average person, I think, probably thinks we should eat lower GI partly because it’ll help us reduce body fat, or partly because it’ll help us avoid weight gain. That links into the whole insulin idea, that it’s like if blood glucose levels spike, theoretically insulin also has to spike to bring blood glucose levels back into range.

We’ve spoken about, previously, how insulin is a bit of a storage hormone and it can help take glucose out of the blood, store it as fat, and amongst other things. But the short answer is, no. The short answer is it doesn’t really affect body composition. I’ll talk through a little bit as to why. Most people would be better off not thinking about it, but I do want to go a bit more nuanced with that. The long answer is that research links it with weight loss in uncontrolled settings.

This is why you’ll often see headlines and stuff like that say lower-GI diets are linked with weight loss, and stuff like that. But part of this is because on average, if you are aiming to consume a lower-GI diet, you’re probably going to end up consuming fewer calories overall, and your diet is probably going to be higher in micronutrients as well, which will carry over to other health benefits.

Part of this is going to be because you will stay fuller for longer. Lower-GI foods are often higher in fiber as well, because fiber slows down the digestion of these carbohydrates, and it takes longer to be converted into glucose in the blood. That raises slower, that makes it lower GI. Where it gets interesting is, we have a lot of research indicating that when total calorie intake is matched, the glycemic index is pretty much irrelevant for body composition.

This is where it gets interesting, because it’s like in uncontrolled settings, you probably want to be aiming for a little bit lower GI, but where it really matters is knowing that because it doesn’t matter, it gives you flexibility. If a large portion of this is because if you eat lower GI, that might mean you are a little bit fuller, but if you get to the end of the day and you’re already relatively satisfied, and you’re faced with the choice of a high-GI fruit versus a low-GI fruit, you can know that it doesn’t matter.

Leah:

There are places where looking at GI does fall apart a little bit. A couple of different factors is, one, there is inter-individual variation, so it’s all based on the average response. When you look at individual scores within the research on this particular topic, there’s a pretty big variation between people’s responses to foods. So, one food might be higher GI for one person and lower for another, and then it could be completely different for another set of foods, which is really interesting to know, that there is this variation just between people.

Aidan:

I think it’s crazy, particularly when you see the numbers, it’ll be like, say, we think of a food as a GI of 70. For one person, it could be like 100, and somebody else is 50. It’s not uncommon to see that in research.

Leah:

… than what you would originally think. Just thinking of giving something a score when you know that there’s that variation between people. There’s also intra-individual variation, in that the same food can have a different effect on you at different times. So, literally the same person, the same food, but potentially other factors going on, like insulin resistance, sickness, stress even, can play a role in the glycemic index of the food, or how quickly your blood glucose levels rise in response to consuming that food.

Which also, again, makes it really complex and interesting. There’s also the other part, talking about fat content. When you have, say, a high-carb food, and then you pair it with something that has a high fat content that’s going to delay digestion and absorption, that is going to affect the glycemic index because it’s delaying the absorption of those nutrients.

So, it’s going to make the blood glucose levels rise at a slower rate, so making the GI lower. There’s all these other aspects of nutrition, so not only fat but also fiber like we talked about, that is going to affect the GI of food. The reason we talk about this is because I feel, like you were saying, there’s this idea that lower GI is better.

But that’s not always going to be the case, because there are foods that are low GI that are high fat, so things maybe like chocolate.

That wouldn’t be considered the most nutrient-dense food to be consuming, but it’s low GI, so we can’t really take it at face value and go, “Low GI equals better always.”

Aidan:

Yeah. I think that’s the most relevant example, because a lot of people do just want to be just focusing on one simple thing, low GI versus high GI. But chocolate’s such a good example.

Because it’s like most people would put that in the quote-unquote ‘bad’ category.

Leah:

100 percent. I think the biggest factor where GI or glycemic index falls apart is it just doesn’t account for total carbohydrate content, which is obviously going to have a huge impact on your blood glucose levels outside of the specific glycemic index of that food. So, the next thing we’ll talk about is something called glycemic load. Basically, glycemic load is the combination of taking glycemic index and total carbohydrates.

It accounts for both of these variables, and it’s basically multiplying the GI score by the total carbs. Technically, you do divide that number by 100, I think just to make it a more simple and nicer number to look at, but at the end of the day it’s talking about the glycemic index but also accounting for total carb intake. Generally, this is going to be a better tool to use when we’re talking about blood glucose levels, because it does take both of those things into account.

Aidan:

Yeah. This is because all forms of carbohydrate break down to glucose in the blood, and glycemic index is a better tool than… sorry, glycemic load is a better tool than the glycemic index, because it becomes interesting when you mix combinations. Like, if you’ve got a high-GI food and a high carbohydrate food, obviously that’s going to raise blood glucose levels a lot.

But what if you get a high-GI food and only a tiny amount of carbohydrate? Everyone could agree if you have a lot of sugar, that’s going to raise your blood glucose levels massively. What if you have a quarter of a teaspoon of sugar? It’s not going to do anything, because it’s just not enough to make a difference. This carries over to other stuff. Using watermelon as an example, technically, watermelon is high GI, but comparatively to a lot of other foods, it’s not super-high carbohydrate.

I think from memory, 100 grams of watermelon has like seven grams of carbs. If you have 100 grams of watermelon, that’s going to raise your blood glucose levels a little bit, but not a lot. If you have more than 100 grams of carbs coming from a low-GI form of rice, this is also where it gets interesting too. Because a lot of people think brown rice is low GI, white rice is high GI. Basmati rice, like white basmati rice-

Leah:

Yeah.

Aidan:

… is lower on average GI than brown rice. Even inside this, it gets complex. If you get a low-GI form of rice and you have a lot of carbs coming from it, that’s going to raise blood glucose levels massively. Because even though it’s low GI and it takes longer to get into the bloodstream and increase… and everything like that, there’s still this massive amount of carbohydrates that has to eventually get in there, and eventually raises it as well.

That’s going to raise it more than a tiny amount of a high-GI food. This is even more relevant for certain conditions. Using diabetes as an example, it could be relevant in that when we’re looking at HbA1c, which is a long-term measure of your blood glucose levels, that’s going to be far, far, far more linked to the total amount of carbohydrate than it is the glycemic index.

If we’re looking at how high your blood glucose levels go as well, that’s once again, glycemia index is going to matter a little bit there or it’s going to matter to a certain great, but total carbohydrates is probably going to matter more. Particularly high glycemic load foods that are high GI and high in carbohydrate.

But also, understanding that gives flexibility as well, in that it means even with diabetes, you can have high-GI foods. It’s not this black-and-white list where it’s like I can only eat low-GI, cannot eat high-GI. You could have a small amount of cake or sugar, or something like that. Just not a lot.

Leah:

Yeah, 100 percent.

Aidan:

You could just have a small amount that doesn’t raise it too much. Both carbohydrate total and glycemic index have their place here.

Leah:

Yeah. So, at the end of the day, most people don’t need to think too much about glycemic index. It’s not something that I would go out of my way to educate every client on, because it’s just not something that most people need. I think, overall, just having a focus on a nutrient-rich diet that’s appropriate in caloric quantity, and macros and micros, is going to matter way more than glycemic index. But for situations where glycemic index does matter, so in cases like diabetes, for example, you are much better focusing on glycemic load instead.

Aidan:

This has been episode 73 of the Ideal Nutrition Podcast. As always, if you could please leave a rating and review, that would be greatly appreciated.