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138: Demystifying the Glycemic Index

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138: Demystifying the Glycemic Index

Apr 18, 2023

Confused about the glycemic index and what it means for your diet? You're not alone. Nutritionist Thunder Jalili joins the Who Cares guys to break down the basics of the glycemic index, its impact on your food choices, and why good nutrition goes beyond just a single number. Discover how to make informed decisions about the food you eat and learn how to balance your meals for a healthier lifestyle.

Episode Transcript

This content was originally created for audio. Some elements such as tone, sound effects, and music can be hard to translate to text. As such, the following is a summary of the episode and has been edited for clarity. For the full experience, we encourage you to subscribe and listen— it's more fun that way.

Scot: Today, it's the episode that everybody has been waiting for. Listeners have been clamoring for this episode. It's likely to be one of our most talked about episodes ever. Today's episode is about . . . Did you want to laugh, Mitch? Usually, you laugh.

Mitch: Oh, no. I'm keeping it under control. I'm hearing what you're saying. I'm hearing the razzle-dazzle. I'm here for it. I'm saying "yes, and" today.

Scot: Okay. Today's episode is about the glycemic index. Sounds pretty fun, huh?

Mitch: Yay.

Scot: Troy, are you excited?

Troy: Yeah. I'm pumped. I can already tell this is going to be our number one episode of all time.

Scot: Is the glycemic index something that you had to learn about in medical school, Troy?

Troy: Oh, if I did, I slept through the lecture. I can't say I've given it much thought beyond that, unfortunately.

Scot: All right. Well, a lot of people may have heard of the glycemic index, but not really fully understand what it means or how it can impact your health. And essentially, the glycemic index is a ranking system for carbohydrates based on how they affect your blood sugar levels.

So foods with a high glycemic index can cause these rapid spikes and crashes in blood sugar levels, which can lead to a range of negative health effects. And also, sometimes it could lead to those crashes that we hear about where you're super tired, don't have energy.

So we're going to learn more about the glycemic index, what it is, how it works, and how you can use it to help with your health, or you might learn it's a bunch of malarkey. I don't know.

This is "Who Cares About Men's Health," with information, inspiration, and a different interpretation of men's health. I bring the BS. My name is Scot Singpiel. The MD to my BS, Dr. Troy Madsen.

Troy: Hey, Scot. Excited to learn about the glycemic index, see what I missed out on in med school.

Scot: Always with his unique perspective, Mitch Sears is on the show.

Mitch: Hey. I guess I've never really actually thought about glycemic index, so I'm actually kind of curious.

Scot: All right. And Thunder Jalili, he's a professor of nutrition and integrative physiology in the College of Health at University of Utah. And he told me this is a good topic, so I'm excited about it. Hey, Thunder.

Thunder: Hi. Hi, guys. Hope everyone's doing well.

Scot: So one of the things we try to do on this show is we try to, as much as possible, make health simple because there can be a lot of noise out there telling you, "You need to do this. You need to do that," while also getting into the nuance when it's necessary.

So my first question is, is the glycemic index useful for men when it comes to their health or does it just complicate things? What's your take on the glycemic index? Is it a useful tool?

Thunder: Yeah. So glycemic index can be moderately useful, and I say moderate because I think sometimes people take it to an extreme. And the index itself is a little limiting because what it does is it ranks foods based on the effect it has on blood sugar levels. So things like sugar and white bread make glucose levels go higher quickly, whereas something like nuts wouldn't have as much of an effect.

So it sounds good on the surface, but one of the things that the glycemic index doesn't really consider is the amount of food that you eat or if you mix that food with other things.

So I say moderately helpful because it kind of identifies which foods have potential to raise blood glucose levels, but you have to consider how much you're eating and what else you're eating with that food.

Troy: So, Thunder, you kind of alluded to it there, but like I said, if I had a lecture on this, I didn't pay attention. What is the glycemic index? I need a starting point here. I'm not even sure.

Thunder: Right. Good question. So glycemic index is basically like you give people a food, a particular type of food, like an apple or a piece of white bread or an egg or something, and then you measure their blood glucose response to eating that food. In other words, how high does their blood glucose get? How quickly does it get high? Things like that.

And you give it a score based on that. The score goes from 0, no effect on your blood glucose levels, to 100, which is a kind of dramatic effect on your blood glucose levels.

I wish I had a table in front of me because I can't remember off top my head what's the food with 100 and what foods have 0, but it kind of goes along with your common sense.

Foods that have more fiber in them and are unprocessed, think of your vegetables and legumes, kidney beans or lentils, things like that, these are low glycemic index foods because they're harder to digest. It's harder to get the carb out of it. The fiber slows everything down, so it takes longer for the glucose to get into your blood.

And then on the other end of the spectrum, foods that have a high glycemic index, so closer to that index of 100, say, 75 to 100, somewhere in that range, these are foods that are loaded with carbohydrates, don't really have any appreciable amount of fiber. They digest very quickly and the glucose hits the blood very quickly.

So what are food examples? White rice is an example, Wonder Bread, potatoes, any kind of soda, like Coke, Mountain Dew, things like that. Those are super high glycemic index foods.

And then stuff in the middle is things that have some fiber in there, but also some easily accessible glucose, like raisins. Maybe a whole grain bread as opposed to a white bread kind of more has a medium glycemic index, so you get some of that glucose hitting your bloodstream in a moderate fashion, not super fast like the high glycemic index ones, but not low like broccoli, for example. So corn, bananas, raisins I think I mentioned, whole grain bread.

So does that answer your question, Troy?

Troy: That's super helpful, yeah. And it makes perfect sense now that you say it. I know we've talked about it before, but while you were talking, I just Googled glycemic index chart. And on the left side of the chart, the low end, I'm seeing things like chickpeas, plain yogurt, peanuts. And then on the high end of the chart, I'm seeing marshmallows, donuts.

Thunder: Marshmallows? Say it's not so.

Troy: I know. Hard to believe.

Mitch: That seems personal.

Troy: Exactly. But it makes sense.

Scot: So is the glycemic index something . . . My impression is that it is going to be more useful as somebody that has insulin resistance, diabetes, pre-diabetes, that sort of thing to make sure that they're eating foods that's not going to cause that insulin response. Or can it be useful to people that don't have those conditions?

Thunder: I think it could be useful for everybody because foods that tend to have a low or medium glycemic index tend to be the foods that we talk about a lot on this show, like foods that make up the Mediterranean diet or those foods that are common in a healthy vegetarian diet.

So I think based on that, it can be helpful for anyone, but you just have to remember this is kind of an artificial index and we do not eat foods in isolation, right? We eat foods in combination and we can vary our amounts.

So, for example, let's say I have a cup of cooked broccoli and I eat that.

Scot: Can we talk about a baked potato instead?

Thunder: I'm getting there. I have a cup of cooked broccoli and I eat that, and it's a very low glycemic index food. All right. Let's say I now have one piece of broccoli and I have a cup of potato. So this is probably more of a high glycemic index meal because even though I have the broccoli in there, it's not much, it's a low dose, and the potato, a whole cup, is a higher dose.

So that's some of the nuance you lose when you just look at glycemic index. We don't eat just one food in isolation. We mix it.

One last example. What if I have a banana, kind of a medium glycemic index food? Well, one banana has kind of that medium effect. What if I decide to eat five bananas? Now the load from that medium glycemic index food is going to be pretty high and I'll actually have more of an effect on my blood glucose levels.

So dosage and how you mix, those are two important things. One spoonful of potato, negligible. Fifty-eight spoonfuls of potatoes, big effect.

Scot: Yummy.

Mitch: That's a lot of potatoes.

Scot: That sounds good. So let's say I love baked potatoes, Thunder. All right? This meal is going to be problematic for a lot of reasons, but let's try to focus on the glycemic index part of it.

I'm a ranch kid, so a steak and a potato, a six-ounce steak and a baked potato. That baked potato's glycemic index from what I've seen can be anywhere from 85 to 95, which on that 100-point scale is pretty high, right? That means those carbohydrates are going to get turned into sugar and utilized really quickly. Is that correct?

Thunder: Yeah. The starch gets broken down really quickly in the glucose, and bam, it hits your blood.

Scot: All right. But I like to put lots of butter and sour cream on my potato. Does that slow down, does that change that glycemic index or that glycemic load? Does it slow down the way my body is going to break that down?

Thunder: It could in the sense that when you add that fat to it, it slows gastric emptying. So, in other words, the potato gets released into your small intestine a little slower, which would slow down the digestive process and the glucose release.

And also, you're throwing that steak in there, right?

Scot: Yeah.

Thunder: So, I mean, if you're a ranch kid, I'm stunned if you have a six-ounce steak. I always thought it'd be much bigger.

Scot: Well, I mean, I never claimed to be a manly ranch kid.

This is a side story. It was always the worst going into the steak restaurant because they'd have the queen size, or the king size, or the bull. And I was always getting the princess size because that's all I wanted. That's all I could eat.

Thunder: That's great.

Scot: But it was probably a more reasonable amount, really, if you're thinking about it, right?

Thunder: Yeah. Better than the cardiologist size.

Scot: Yeah.

Thunder: Yeah, but that affects glycemic index. Even the steak you throw in there, it takes a while to digest, to pass that protein in the steak into the small intestine. Again, that slows gastric emptying. So things like that could moderate the potato effect.

Scot: Sure. And like I said, there are probably other dietary problematic issues with that with the amount of butter I probably like in eating that steak, but I think that illustrates the fact that it does change things.

So, for example, if I have dessert after my meal, as opposed to before my meal, that dessert would have an high glycemic index, but because I've had a meal on a full stomach, would that slow down? Would that change things?

Thunder: I don't know, because desserts typically have so much sugar in there. Maybe of a dessert with 30 grams of sugar, 40 grams of sugar, that's already available and ready to hit your bloodstream pretty much. At least the potato has to be broken down. The starch in a potato has to be broken down into smaller units and eventually to glucose. You don't have that with chocolate cake. It just has a ton of sugar.

Scot: Troy, you know what my takeaway from that comment is?

Troy: You should eat more stuff to slow down the high glycemic index stuff.

Scot: Oh, no. No, because that doesn't work. You should eat dessert first. Life is short.

Troy: There you go.

Thunder: Or just have a smaller dessert, right?

Troy:I was going to say . . .

Thunder:Dosage/amount is also important for glycemic index. I can have one bite of chocolate cake. It's not a big deal for anything . . .

Scot: Who does that?

Thunder: . . . because it's so little.

Mitch: That's what I was going to say. Who does that?

Thunder: I know, but just as an example, right? It's such a high glycemic index food, but I have one bite, it doesn't have any impact.

Scot: Yeah. Or a smaller slice perhaps.

Thunder: Yeah. So, like I said, I keep going back to this. That's the one problem with glycemic index. It identifies foods that have the potential to really play this role on your glucose levels, but there's so much nuance, like how much of the food you're eating and how are you mixing it with other stuff. And that's the limitation of glycemic index.

Scot: Here's another problem I have with glycemic index. I'm going to play a little game with you guys. What's going to have a higher glycemic index? A chocolate bar or a baked potato? Troy.

Troy: Since you're asking the question, the answer is going to be baked potato.

Mitch: No. I'm going to do the opposite, chocolate bar.

Scot: All right.

Mitch: Wait. How much cacao? What is the rating? How dark is it?

Scot: So the glycemic index for a milk chocolate bar is 42. If it's dark chocolate, it's 23, which is pretty low. That's shockingly low, right?

Troy: Surprisingly low.

Thunder: Well, that dark chocolate bar has fiber in it too.

Scot: Oh, okay.


Scot:A baked potato is 85 to 95. So are you telling me the glycemic index is saying I should eat those chocolate bars before that baked potato?

Thunder: Well, also if you look back at that, wherever you got that data, Scot, what's the serving size for the dark chocolate? Is it the whole bar? Is it just one square that's, like, five grams or something?

Again, you're talking about how it affects the glucose levels that come into your blood. If you have five dark chocolate bars, then maybe the glycemic load will be much higher than just a couple of squares off of one bar.

Scot: All right. The other one that surprised me here is . . . and you guys are already onto my game, so we don't need to play it, I suppose. A soda or a baked potato? Now, the chart I saw, a soda is 59, but there again, now I'm learning that we don't have a serving size. That might be an ounce, right? And a baked potato is 85 to 95. That just seems really strange.

Thunder: I just see here . . . I Googled a glycemic index chart with serving size. The Coke is a 12-ounce serving size. And then what are the carbohydrates? So there are roughly 40 grams of sugar in a soda, and the glycemic index is 58 for one 12-ounce Coke.

Scot: That makes no sense. I would think that that would be so much more likely to cause a blood sugar spike than a baked potato.

Thunder: Well, let me give you some good news.

Scot: Okay. Please.

Thunder: One 12-ounce beer would have a lower glycemic index than Coke, because I see here if you have 25 ounces of beer, 2 cans, the glycemic index is 66. So if you have one can of beer, it's probably a lower glycemic load and probably a better glycemic index.

Scot: Wow. All right. So we're learning some stuff here. What do I do with that? Does that mean given the choice, I should have a beer over a Coke?

Thunder: Well, I would say yes.

Mitch: And put butter on that beer . . .

Troy: Put butter on it.

Mitch: . . . to make it go faster.

Thunder: Yeah, mix some butter in the beer. But don't lose sight of the big picture. These are foods in isolation. And again, we eat stuff that's mixed together, right?

Scot: So what is your trend?

Thunder: Yeah. What is your trend? So if you have oatmeal with a glycemic index of 58, kind of a moderate glycemic index food, but you're putting nuts in there that have fiber and fat and you have an egg with that oatmeal, now you're talking your whole meal probably has a lower glycemic index. And am I having half a cup of oatmeal or 10 cups of oatmeal? That affects the glycemic load.

So just remember what are you mixing your food with and how much of it are you eating?

Scot: Is the glycemic index useful in another way other than just kind of trying to figure out how fast this meal is going to be converted into sugar and what kind of insulin response I'm going to have, what kind of sugar crash I might have?

Thunder: Yeah, I think one of the things it's useful for us to provide another piece of guidance to tell us what foods are more healthy and what foods are less healthy.

Foods that have a lower glycemic index will have more fiber, they're typically less processed, and so they can be identified by the index score. And foods on the other side of the scale that have high glycemic index, typically they have less fiber. They may be more refined or more processed. So it labels those.

So maybe don't get hung up on the exact number, but you can kind of put foods in groupings, like a low, medium, high. And things that are high, say, "Okay. I'm going to try to not eat as much as those," and just focus on the ones that are low and medium and not worry about the exact number.

Foods in general that we consider healthy, that are on the lower glycemic index, people follow this and it can also help in weight loss. We haven't really talked about that.

You look at the stuff that has high glycemic index foods. I'm looking at a list right now. Fruit Loops, for example, 69. That also has a lot of added sugar. Any kind of dessert . . . You eat less of this stuff, you eat less added sugar, you probably end up losing weight.

For some people, weight loss also is accompanied by a lower blood pressure, right? So you get kind of some added bonuses.

So it can be a guide in that sense. I'm going to try to pick more of these lower GI foods just because I know those are the ones that will help with weight loss and kind of help long-term with overall health. But not to get hung up on, "This food is 50. This food is 54. I cannot eat the 54. I've got to go with the 50." Don't get that hung up with the numbers, but use it as a guide.

Scot: Sure. And it also sounds like if something is low on the glycemic index, I can eat a lot of that. It probably is not going to be a big deal. If it's higher, I probably want to watch my portion size.

Thunder: Very well put.

Scot: Yeah. All right. Hey, Mitch?

Mitch: Yeah.

Scot: So was this the groundbreaking episode that I promised?

Mitch: As someone who has struggled with weight and nutrition in the past, it's comforting, I guess, but also frustrating to hear there is no simple answer.

But at the same time, eating more unprocessed things, making sure that it's balanced, making sure that you're getting enough calories every day, etc., is maybe more important than following every little number that exists out there, whether it be a point system in some weight scale, or the glycemic index, or if it fits your macros. All of those really number-focused things about nutrition, it doesn't necessarily give the whole story.

So there's a bit of comfort in that, being like, "Okay. So this could be a helpful tool, but it is not a commandment of how I'm going to lose weight."

But at the same time, it could be really helpful and it just sounds like we're back to unprocessed foods again.

Scot: Yeah. I think my takeaway is I could get into this game where I'd be like, "Oh, I've got to pick the lowest foods on there to be as healthy as I can." Right?

Mitch: Oh, yeah.

Scot: I totally could get into that game. But I think my takeaway is it's a good thing to take a look at. And try to focus on having a lot in the lower glycemic index than the middle, and try to have fewer calories that are coming from that upper part.

I think it's just another way to kind of tell how are you doing and you don't have to play the points game. It's just kind of a general chart of, "This is going to cause less blood sugar spike. This is going to cause more."

Troy, takeaway?

Troy: Yeah, I've been interested just because looking at these charts, some of the foods did surprise me a little bit that are on the higher end. So maybe I'll think a little bit more about those foods. For example, cheesy crackers. I guess it makes sense that that's on the higher end of the glycemic index, but I might not have thought as much about that before.

So that's probably my takeaway. I may think a little bit more about some of these foods that are on that higher end, but it's not going to be something I spend a ton of time changing my diet for.

Thunder: Cheesy crackers. Thank you for bringing that up.

Troy: Of course.

Thunder: Well, that's a great example because you have a few cheesy crackers, but you have other things in that snack. And so you think about what you mix your high glycemic index foods with, and that lowers the overall meal glycemic index. So we can't lose sight of that. It's okay to have some of these things that are high.

Watermelon has a high glycemic index, right?

Troy: Yeah, that surprised me.

Thunder: But it's water. It's mostly water. So the actual load that your body experiences is quite low because it's mostly water.

So that's why you have to take this glycemic index with a little bit of caution. Just use it as a guide, and if you want, use it to mix your foods together so you know your overall load of the meal is moderate or low. But don't think of it just for that one food by itself.

Troy: So you're saying marshmallows plus watermelon, not a good meal.

Thunder: Yeah, or marshmallows . . .

Scot: Or cheesy crackers, really.

Troy: Cheesy crackers dipped in marshmallow.

Thunder: A marshmallow sandwich with cheesy crackers.

Troy: Not wise.

Scot: Oh, boy. All right. Thunder, you're our expert. I mean, I wouldn't imagine you had any takeaways because you gave us all the information, but any takeaways from this conversation?

Thunder: Yeah. My takeaway is I use glycemic index as a guideline of what foods to eat a little less of and what foods to try to emphasize, but I don't get overly hung up on it. So that's my takeaway.

Scot: Have you ever experienced what we're talking about? Do you have a question about the food you eat? Have you found a diet claim on the internet that just seems too bizarre to be true and you want to know what's really going on? We would love to hear from you and you can reach out to us via email at That's

Thunder, thanks for being on the show.

Thunder: Yeah, it was a pleasure to be on and talk with you all.

Scot: And thanks for caring about men's health.

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