Don't be fooled by its size with its large bulb and long leaves. The leek is flavorful but not overpowering, and is considered the mildest of all the onions. A traditional ingredient in French cuisine, the leek adds not only onion flavor to your food, but also a hint of garlic. Like other vegetables, leeks are low in calories and chock full of nutrients you need for good health.
One leek, which weighs 89 grams, contains just 50 calories. With 0.6 calories per gram, the leek is a very low-energy-dense food, and is a good way to add flavor to foods such as soups, stews, grain dishes and omelets without adding a lot of calories. In general, most people eat about the same weight in food regardless of calories. Low-energy-dense foods have fewer calories per gram and can help you feel full on fewer calories, and assist with weight loss.
Carbs, Fiber and Sugar
Carbohydrates provide most of the calories in the leek, and as a sweet onion, some of the carbohydrates are in the form of sugar. One leek contains 13 grams of carbohydrates, 3 grams of sugar and 2 grams of fiber. While you might be concerned about the sugar in the leek, its other natural benefits -- such as the fiber -- outweigh any harm. The fiber in the leek is a non-digestible carbohydrate that keeps you feeling full and helps prevent constipation. Getting more fiber in your diet may lower your risk of heart disease, Type 2 diabetes and obesity.
Protein and Fat
The leek is fat-free and contains a small amount of protein; 1 gram in one leek. While you might think Americans are lacking in protein, most get more than enough in their diet, according to the Centers for Disease Control and Prevention. Women need 46 grams of protein a day, and men 56 grams. While vegetables like leeks are a source of protein in your diet, they are not a complete source of protein because they do not provide all of the essential amino acids.
Vitamins and Minerals
Leeks may be low in calories and protein, but they are an excellent source of vitamins A and C, a good source of iron and even contain a small amount of calcium. Vitamin A is essential for vision, helping you see colors and at night. Both vitamins A and C also help keep your immune system strong and help you fight off infections. Iron and calcium are both essential minerals you need for good health. Iron carries oxygen to all the organs, muscles and tissues in your body, while calcium helps keep your bones and teeth healthy and strong.