Calculating Glycemic Index

Jessica Rice

Hi, my husband has been recently diagnosed with pre-diabetes. I've done some online research in the short time since that announcement, and I've found out that the glycemic index of foods is super important to maintaining healthy blood sugar levels.

My question is how does one figure out the glycemic index of a food from a nutrition label? I've found lots of information on the glycemic index of whole foods like a banana or a potato. What I would like to figure out is the glycemic index of packaged grocery store foods? Does anyone know of a formula, or even an app that calculates it for you?

Sawyer Paull-Baird

Hey @Jessica Rice.

Due to the medical nature of the question, I think @Bella Diaz would be the best person to answer this question. Tagging her here so she can see it soon.

In the meantime, here is a decent resource on both Glycemic Index, and Glycemic Load (the difference is explained at the link). Here's another with a more extensive list. I know these don't give you exactly what you're looking for regarding a way to go from nutrition label to GI, but I amnot aware of such a tool. Bella may though if one exists? Another option is to have a list of "go-to" carbohydrate options you know are lower GI foods, and try to stick to those items most of the time.

Feeling proud of this forum community that we can in such a short time be a resource for something as important as this.

Confident we can get you and your husband some great tools here.

Hope you had a great Thanksgiving.

Sawyer

Mike Stack

@Jessica Rice, this is a very good question, as glycemic index is a popular tool in managing blood sugar levels. That being said, I don't know if it's the most useful tool practically speaking. Let me explain.

First, we need to have an understanding of what glycemic index (GI) is. The easiest way to think of it is as follows; it's basically the carbohydrate's speed limit for entering the blood stream. The higher the GI number the faster it will enter the blood stream. Now on some level it stands to reason that the higher number, the faster it enters the blood stream, the more your blood sugar levels will rise. This is only partially true. Another factor called glycemic load (GL) comes into play here. This is the AMOUNT of carbohydrate consumed or how dense the food source is with carbs. Fruits, as an example, can have a high to very GI, because fruits are mostly compromised of fructose (fruit sugar), so their speed limit will be high for entering the blood stream. That said, fruits tend to not have a lot of energy associated with them (because they're mostly water and fiber), therefore their GL is relatively low. Lastly, with regard to calculating GI itself, the assumption, clinically speaking is that the food is consumed in isolation (meaning without any other food sources). So you're consuming a piece of bread by itself, an apple by itself, or a cookie by itself. Now while this may be the case sometimes it is not often the case (i.e., you're having two pieces of bread with a sandwich or a potato with a full dinner). So based on what I've said above, I think GI is a good item to look in theory (like in a lab), but I don't know how practical of a measure it really is to look at if you're talking about managing diabetes effectively. I think this is one of those times where the intent of science was good (to provide useful information), but in practice the information is not as helpful as what we hoped it would be.

With all of that said, I'd actually encourage you to NOT jump right to GI as a way to manage diabetes (or in your case pre-diabetes). It seems like an effective and attractive thing because it's just a simple number. However, as you can see from what I've mentioned above it's an over-simplication of a more complicated concept. I think this is why GI has fallen out of favor, practically, with many diabetes management experts. It provides just enough information to seem like it's useful, but in reality not be that effective (which just makes it confusing). Below I've listed some more effective practical management strategies for diabetes. I would suggest focusing on these first before you start to consider GI (or even GL):

1) Physical activity and exercise: If there is one thing we know about managing diabetes and blood sugar levels it's that movement and exercise is king. Moving more drives sugars into the muscles without the aid of insulin (which is what is overtaxed in the case of diabetic). Movement (have it be in the form of just physical activity or more formal exercise) is the best way to regulate to blood sugar levels. This the first-line treatment in the minds of many medical professional. With that said, I would first focus on getting in as close to 10000 steps per day (or at least as close to that number as you can get). Another way to think of this is to get in about 30min of physical activity. Beyond that, adding in formal exercise is also very effective, as these bouts of higher intensity activity help to regulate blood sugar levels in the hours after exercise as well. Side note here, strength training is amazingly effective at long-term blood sugar regulation and diabetes management as it builds important muscle that helps to more effectively store sugar in the body.

2) Focus on consuming whole/unprocessed/minimally processed foods: This kind of gets back to your GI question, except gives you a better construct for thinking about it (at least one that's more practical and easier for you to follow). Whole foods that haven't gone through a lot of processing (such as fruits, vegetables, and whole grains) have a limited impact on raising blood sugar. They simply take longer to digest and absorb in the human body, therefore their energy (sugar) is released into the blood stream at slow rate, which causes a smaller rise in blood sugar. Even fruits that might have a higher GI (like watermelon for example) result in a pretty minimal increase in blood sugar, because there is such a small amount of energy in watermelon (this is the concept of GL which I mentioned above). So in terms of food choices think of things around the outer edges of the grocery store, fresh fruits and vegetables especially. If you're looking for carbs to eat try to stay away from the "snack" type carbs (cookies, crackers, chips, etc.). The more you can focus on whole grain carb sources the better. In summary to this point, basically make healthy food choices. At the risk of over simplifying things myself here, I do think is such a critical step that most people don't take the time to think about. Many people overcomplicated things with GI, GL, looking net carbs and so on then miss the larger point. Eating minimally processed or whole food sources is the best way to control blood sugar and eat a healthier, "diabetic friendly," diet.

3) Limit snacking: One of the best ways to get blood sugars up is to eat frequently. Every time you eat something blood sugar levels rise (no matter what it is that you eat, even protein or fat), so with that said a lot of snacking during the day can drive blood sugar levels up unnecessarily. At one time we used to think that small snacks were a great way to regulate blood sugar. Now, thanks in part to the intermittent fasting research, we realize this not true. The best way to regulate blood sugar and improve insulin sensitivity (an important clinical factor is diabetes management) is to NOT eat often. The old six small meals per day is probably contributing to more diabetic issues than it's helping. I don't think this means you can't snack during the day or eat if you're hungry. I just think this means you need to be smart about it. Don't just eat a bunch of times during the day because you've heard this helps to stabilize blood sugar (or boost metabolism or any other claim that small meals more often is better), because it doesn't. In fact, it does the opposite. When you want to snack during the day (or when it's time to eat) eat a balanced meal/snack with all nutrients, not just carbs.

4) Try to consume protein and fiber every time you eat: Piggybacking on my statement at the end of number three, have it be a snack or a meal, protein and fiber slow digestion and absorption in the human body. So if you're going to have a snack having a cheese stick (protein) and an apple (fiber) is a great way to slow the entry of the carbohydrate into the blood stream, thus causing a small rise in blood sugar. Avoid snacks (and meals) that are carb-only (or even carb heavy) is a great way to improve blood sugar management. Think of dividing your plate into sections, a large section for something fiber-based (vegetables or fruit), a moderate section for protein, and a smaller section for carbs. This is the best way to construct a meal (or a snack) to manage blood sugar levels.

In summary then, I would say this. Don't worry about focusing on GI (or even GL) right now, particularly not in the pre-diabetic stage. Yes, in advances cases of diabetes, where symptoms are much more severe and the consequences of poor regulation are more dire you may need to focus on GI, but not at this point (and hopefully not for a while if you do what I've outlined above). Focusing on getting more physical activity and exercise, eating a diet rich in whole/minimally processed foods, limiting snacking, and always having protein and fiber every time you eat is the best way to effectively manage pre-diabetes (and even early onset diabetes).

I hope you found this helpful. Let me know if you have any other questions on this.

Jessica Rice

This is great information, and written in a way that is easy to understand. Thank you!

Mike Stack

You're welcomed @Jessica Rice! I'm glad it was helpful :)