A medium ear of fresh corn contains about 243 mg of potassium, which is roughly 5% of the recommended daily intake of 4,700 mg. That places corn in the moderate range for potassium, not especially high or low compared to other vegetables. The exact amount shifts depending on whether you’re eating it fresh, frozen, or canned.
Potassium by Serving Size and Form
How you buy and prepare corn changes its potassium content more than you might expect. Here’s how the most common forms compare:
- Fresh corn on the cob (1 medium ear): 243 mg potassium
- Frozen corn kernels (½ cup): 195 mg potassium
- Canned corn (½ cup): 108 mg potassium
- Air-popped popcorn (3 cups): about 79 mg potassium
Fresh corn naturally has the most potassium per serving. Frozen kernels retain a good portion of it since they’re flash-frozen shortly after harvest. Canned corn loses some potassium to the liquid it sits in, and draining that liquid removes even more. Interestingly, one University of California study found that vacuum-packed canned corn sometimes tested slightly higher in potassium than fresh or frozen samples, likely due to variability in growing conditions and testing methods. In practice, though, the USDA data and most nutrition databases show canned corn on the lower end.
How Corn Compares to Other Vegetables
At around 243 mg per ear, corn sits in the middle of the pack. A medium banana, the go-to potassium reference, has about 422 mg. A medium baked potato delivers roughly 926 mg. On the other end, a half cup of green beans has around 90 mg. So corn gives you a decent potassium boost without being one of the heavy hitters.
For context, most adults need 4,700 mg of potassium per day. One ear of corn gets you about 5% of the way there. You’d need to eat corn alongside other potassium-rich foods throughout the day to hit that target, which is true of most individual vegetables.
Fresh Corn Is Naturally Low in Sodium
One thing worth noting: fresh corn has very little sodium. A medium ear contains just 13.5 mg, giving it a favorable potassium-to-sodium ratio of roughly 18 to 1. That ratio changes significantly with canned corn, which often has salt added during processing. If sodium is a concern for you, rinsing canned corn under water before eating it can reduce the sodium content by about a third while keeping most of the potassium intact. Frozen corn, which typically has no added salt, is a better option if you want something close to fresh.
Corn and Kidney-Friendly Diets
People managing kidney disease often need to track potassium carefully. The American Kidney Fund includes corn in its potassium food guide, listing canned corn at 108 mg per half cup and frozen kernels at 195 mg per half cup. Neither of those amounts is considered high potassium by most renal diet standards, where “high” typically means over 200 mg per serving.
Canned corn, in particular, tends to be one of the more kidney-friendly vegetable options because the canning process leaches potassium into the liquid. Draining and rinsing reduces the potassium content further. Frozen corn is still reasonable but lands closer to that 200 mg threshold, so portion size matters more. Fresh corn on the cob, at 243 mg per ear, crosses into moderate territory and may need to be limited depending on your individual potassium target.
Popcorn as a Low-Potassium Snack
Popcorn is technically corn, but it behaves very differently nutritionally. A full 3-cup serving of air-popped popcorn contains only about 79 mg of potassium. That’s less than half of what you’d get from a half cup of frozen kernels. The reason is simple: popcorn is dried corn with most of its water removed, and a 3-cup portion of popped kernels weighs very little, roughly 24 grams. You’re eating far less actual corn by weight than you would with a cob or a scoop of kernels. If you’re looking for a snack that won’t add much potassium to your daily total, plain air-popped popcorn is a solid choice. Adding butter or flavored toppings won’t change the potassium much, though it will affect sodium and calories.