Popcorn is a feel-good snack strongly associated with relaxing, watching movies and escapism. If you don’t drench the popped kernels in butter or processed toppings, it’s also a fairly low-calorie snack. Popcorn’s glycemic index, which is a measure of how much a food impacts blood sugar levels, can fall on the lower side of the spectrum, depending on the brand and how it’s made.
The glycemic index is a useful tool that rates food based on its ability to increase blood glucose levels, which in turn is an indication of pancreas stimulation and insulin release. Insulin is needed to shuttle glucose from your blood into all your cells, where it’s used to produce energy. The glycemic index is particularly important for diabetics because they either don’t produce enough insulin or are resistant to its actions. As such, low glycemic foods are commonly recommended for diabetics and people who want to lose weight. The glycemic index is a scale that ranges from zero to 100, and foods at or below 55 are considered as having low impact on blood sugar. Foods with an index score higher than 70 are quickly digested into glucose and increase blood sugar, which spikes insulin release.
Popcorn’s glycemic index is actually quite variable. Most popcorn brands range from 55 to 65, although some are as high as 89, depending on the type of corn, added ingredients and the method of cooking. Plain, air-popped popcorn tends to have the lowest glycemic index ratings, whereas the stuff typically sold at movie theaters is significantly higher. It’s mainly the starchy carbohydrates in corn that get converted into glucose and increase blood glucose levels. As a general guideline, you can make popcorn at home that’s a borderline low glycemic snack or you can purchase it pre-made at the theaters, but buyer beware!
The glycemic load is another type of food measurement that takes into account the type and quantity of carbohydrates in the food you eat. Because popcorn expands when cooked and is fairly filling due to the fiber content, the portions normally consumed tend to be relatively small. As such, the glycemic load of popcorn is probably a better indicator of blood glucose impact than its potential glycemic index. For example, prepared popcorn that has a relatively high glycemic index of 70 actually has a fairly low glycemic load of 8 because popcorn is low in carbohydrates per the typical portion size of 1.5 cups. On the other hand, if you eat a mound of popcorn the size Mt. Kilimanjaro, then the glycemic load will dramatically increase.
Although corn is fairly high in starch, about 20 percent of the carbohydrate content in popcorn is fiber. Most dietary fiber is undigested and doesn’t impact blood glucose levels, but it’s very helpful for promoting regular bowel movements and combating constipation. In addition to being fairly filling, plain, air-popped corn is also low fat and very low in calories – it has approximately 40 calories in 1.5 cups. Without butter and salt, popcorn may be a little boring, but staying healthy has its sacrifices. You could add other seasonings such as cinnamon or garlic powder, though.
- American Dietetic Association Complete Food and Nutrition Guide, 3rd Edition; American Dietetic Association
- Contemporary Nutrition: Functional Approach; Gordon M. Wardlaw et al.
- Encyclopedia of Human Nutrition; Benjamin Caballero et al.
Sirah Dubois is currently a PhD student in food science after having completed her master's degree in nutrition at the University of Alberta. She has worked in private practice as a dietitian in Edmonton, Canada and her nutrition-related articles have appeared in The Edmonton Journal newspaper.