mint leaves are similar to other leafy greens. A cup of fresh spearmint leaves, for example, has just 40 calories. That calorie investment nets you 3 grams of protein, as well as about a gram of fat. Mint leaves also contain some carbs – 8 grams in total. However, 6 of those grams come from dietary fiber, which fights off constipation, promotes healthy blood cholesterol levels and keeps you feeling full. The fiber in a 1-cup serving of spearmint leaves covers between 16 and 24 percent of your daily needs, depending on your sex and age.