Salads are often hailed as a health food, in large part due to their base: raw, leafy greens. Leafy greens are packed with nutrients, delicious, and an important part of a healthy diet. This superfood group of vegetables includes a variety of leaves in different colors, shapes and sizes.

At the grocery store, you'll find a wide selection of greens: from soft butter lettuce to spicy arugula, crunchy romaine and tender baby spinach. Which salad greens are the healthiest? We spoke to dietitians about the leafy greens with the most health benefits, which greens are the least nutritious, and how to build a healthier salad. Leafy greens are packed with vitamins, minerals and antioxidants, Amy Kimberlain, registered dietitian and spokesperson for the Academy of Nutrition and Dietetics, tells TODAY.

com. These include vitamins A, C, E and K; calcium; potassium; iron; magnesium; folate; carotenoids; and flavonoids — "all of which have been shown to be of benefit in reducing many chronic health conditions," Kimberlain adds. The health benefits of leafy greens include supporting the immune system, boosting heart and brain health, maintaining strong bones, fighting inflammation, protecting vision and more.

"They are also very low in calories, carbohydrates, fat, provide some protein and are a good source of fiber," Julia Zumpano, registered dietitian at the Cleveland Clinic, tells TODAY.com. Dietary fiber helps to prevent constipation and regulate blood sugar, and aids with weight loss.

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