Corn is a surprisingly nutrient-dense grain, packing B vitamins, eye-protective antioxidants, and a solid dose of fiber into every ear. A 100-gram serving of boiled yellow sweet corn (roughly one medium ear) contains 96 calories, 21 grams of carbohydrates, 3.4 grams of protein, 2.4 grams of fiber, and 1.5 grams of fat.
Carbohydrates, Protein, and Fat
Most of corn’s calories come from carbohydrates, primarily starch with a smaller amount of natural sugars. Sweet corn has a glycemic index of 52, which places it in the low-to-moderate range. A medium ear carries a glycemic load of about 15. That means it raises blood sugar more gradually than white bread or white rice, partly because its fiber and starch structure slow digestion.
The 3.4 grams of protein per 100 grams is modest compared to beans or meat, but respectable for a grain. Corn protein is lower in certain essential amino acids (particularly lysine and tryptophan), which is why traditional diets pair it with beans. The fat content is minimal at 1.5 grams, mostly unsaturated.
B Vitamins: Thiamin, Folate, and Niacin
Corn is a strong source of several B vitamins. A single large ear of raw sweet corn provides about 0.29 mg of thiamin (B1), covering roughly a quarter of most adults’ daily needs. Thiamin helps your body convert food into energy and plays a role in nerve function. The same ear delivers around 66 micrograms of folate (B9), which supports cell division and is especially important during pregnancy.
Corn also contains niacin (B3), but here’s the catch: in raw or simply boiled corn, much of the niacin is chemically bound in a form your body can’t absorb. This is why populations that historically relied on corn as a staple sometimes developed pellagra, a niacin deficiency disease. The workaround, discovered centuries ago in Mesoamerica, is nixtamalization: cooking corn kernels in an alkaline solution (water with calcium hydroxide, or lime). This process frees the niacin and makes it available for absorption, while also boosting calcium content. A 100-gram serving of a corn tortilla made this way contains about 93 mg of calcium, compared to negligible amounts in plain boiled corn.
Key Minerals
Corn delivers meaningful amounts of several minerals. Per large ear of sweet corn, you get approximately 53 mg of magnesium (about 13% of the daily value) and 127 mg of phosphorus (around 18% of the daily value). Magnesium supports muscle and nerve function, while phosphorus is essential for building bone and generating energy at the cellular level.
Lime-processed corn products go further. A 100-gram serving of traditional corn tortillas provides roughly 2.5 mg of iron, 2.5 mg of zinc, and 70 mg of magnesium. The alkaline processing not only frees up niacin but also changes the mineral profile, particularly by adding calcium from the lime itself.
Antioxidants That Protect Your Eyes
Yellow corn is one of the richest vegetable sources of two carotenoids called lutein and zeaxanthin. Fresh golden whole-kernel corn contains about 330 micrograms of lutein and 209 micrograms of zeaxanthin per 100 grams. These are the only two carotenoids found in the macula, the central part of your retina responsible for sharp vision. They act as a natural filter against blue light and neutralize free radicals in the eye. Higher dietary intake of both is linked to lower risk of cataracts and age-related macular degeneration, the leading cause of blindness in older adults.
White sweet corn, by comparison, contains dramatically less: only about 5.5 micrograms of lutein and 28.5 micrograms of zeaxanthin per 100 grams. If eye health is a priority, the deeper yellow the corn, the better.
Fiber: Mostly the Insoluble Kind
Corn’s 2.4 grams of fiber per 100-gram serving is predominantly insoluble. USDA measurements of yellow corn on the cob show roughly 4 grams of insoluble fiber for every 0.1 to 0.25 grams of soluble fiber, depending on the variety. Insoluble fiber is the type that adds bulk to stool and helps food move through your digestive tract. It’s also the reason corn kernels often appear intact in stool: the outer hull (pericarp) is made of cellulose that human enzymes can’t break down, though the nutrients inside the kernel are still absorbed.
Resistant Starch and Gut Health
Corn contains resistant starch, a type of carbohydrate that passes through your small intestine undigested and feeds beneficial bacteria in your colon. When gut bacteria ferment resistant starch, they produce short-chain fatty acids, particularly butyrate. Butyrate increases blood flow to the colon, lowers its pH, and has shown protective effects against colorectal cancer in research settings.
How you prepare corn affects resistant starch levels. Cooking and then cooling corn (or corn-based foods) increases the amount of resistant starch that forms as the starch molecules reorganize during cooling. Frying corn-based patties at high temperatures also increased resistant starch content from 4.3% to 5.4% in one study. On the other hand, extrusion processing (the kind used to make many puffed corn snacks) tends to decrease resistant starch. If you want to maximize this benefit, eating leftover cooled corn or chilled corn salad is a simple strategy.
Purple and Blue Corn Varieties
Not all corn is yellow. Purple corn, grown primarily in Peru, Mexico, and parts of Asia, contains anthocyanins, the same class of pigments found in blueberries and red cabbage. The concentrations are striking: purple corn kernels can contain anywhere from 56 to 1,970 mg of anthocyanins per 100 grams of dry weight, depending on the variety and growing region. The cobs themselves are even more concentrated, with Peruvian varieties reaching 2,600 to 3,800 mg per 100 grams.
Anthocyanins are potent antioxidants with anti-inflammatory properties. Purple corn is traditionally used in drinks like chicha morada in Peru and is increasingly available as a powder or flour. While it shares the same basic macronutrient profile as yellow corn, the anthocyanin content sets it apart as a nutritionally distinct food.
What Processing Changes
The way corn is processed significantly alters its nutrient profile. Nixtamalization, as mentioned, unlocks niacin and adds calcium, but it comes with trade-offs: B-vitamin losses during lime cooking range from 30% to 70%, with about half of thiamin lost during the cooking and steeping steps alone. Canning corn reduces carotenoid levels compared to fresh. Freezing tends to preserve nutrients better than canning.
For the most complete nutrient package from standard yellow corn, eating it fresh and close to harvest gives you the highest levels of carotenoids and B vitamins. For niacin availability and calcium, nixtamalized products like traditional tortillas and masa are the better choice. No single preparation method wins on every front, which is one reason corn appears in so many forms across world cuisines.