Green bananas and plantains are high in resistant starch, which promotes a healthy balance of gut bacteria. They are also high in fiber, so they keep your bowels in working order. As both fruits ripen, the starch begins to turn to sugar (via WebMD). While a 100-gram serving of green plantain has 152 calories, 37 grams of carbs, and 2 grams of sugar, a 100-gram yellow plantain has 122 calories, 32 grams of carbs, and 18 grams of sugar. Meanwhile, 100 grams of a slightly ripe banana will have 98 calories, 23 grams of carbohydrates, and 16 grams of sugar.
A banana is known for its potassium, and it offers 326 milligrams of this nutrient that helps your body maintain its fluid balance and regulates your heartbeat. Plantains have slightly more potassium with 487 milligrams and 50% more vitamin C.
Plantains and bananas have relatively low glycemic indices, which means they are good for people with diabetes because they don’t spike your blood sugar. The low GI threshold is below 55, and plantains have a GI of 40 (via WebMD). The glycemic index of bananas depends on their ripeness. While they can range from a low GI of 47 to 53, an extremely ripe banana can peak at 57, which is a medium GI (via Glycemic Index).