The short answer is it can be either super healthy or very unhealthy, depending on how you prepare it. 1 cup of pure, unflavored air-popped popcorn has about 30 calories, no fat, no sodium, and about 1 gram of fiber. In terms of impact on blood sugar or carb count, corn has a moderate glycemic load—less than potatoes but more than peas and lentils.
Corn provides B vitamins, zinc, copper, potassium, magnesium, phosphorus, iron, zinc, manganese, and polyphenol antioxidants helpful in reducing heart disease. It’s a more satisfying and filling snack than processed foods like potato chips, because it’s a whole grain and contains fiber. It’s also naturally whole grain, sugar-free, and low in calories (without all the toppings).
The picture starts to change once you get into packaged, microwave, or movie theater popcorn, where added salt, butter and oil, calories, and flavoring additives start to become an issue. Often in microwave bags there is trans fat, which is the type of fat that is most inflammatory and has been deemed truly unhealthy. Also there is concern (although not yet definitive proof) that the Teflon-like coating in microwave bags can get broken down with heat into potentially carcinogenic substances and emit fine particles that may be associated with lung disease.
Portion control with microwave popcorn and movie popcorn can easily go out the window. A typical bag of microwave popcorn contains 10 cups and movie popcorn 9-20 cups. As with most snack foods, moderation is the key.
Those who advocate avoiding the high-heat cooking of oils express concern that popping popcorn at high temperatures can cause the oil to oxidize, increasing its inflammatory properties.
How can you make your popcorn snack be healthy and still delicious? Try air-popping your own popcorn by putting 1/2 cup of kernels in a brown paper bag and popping in the microwave for 1 to 1 1/2 minutes, or when the corn popping slows down. Then dress it up with grated parmesan, chili powder, nutritional yeast (for a vegan cheese flavor), olive oil, garlic or onion powder, and other herbs and spices.
For a sweet snack, mix dark chocolate shavings and some cinnamon. If you want to pop your corn in oil rather than drizzling the oil on after it’s popped, use coconut oil, which is stable at high temperatures.