"Greens are the No. 1 food you can eat regularly to help improve your health," says Jill Nussinow, MS, RD, a culinary educator in Northern California. That's because leafy vegetables are brimming with fiber along with vitamins, minerals, and plant-based substances that may help protect you from heart disease, diabetes, and perhaps even cancer.

Despite the fact that we know we should eat more green veggies, do you?

To encourage you to put more leafy vegetables on your plate, WebMD asked Nussinow to rank the country's most widely-eaten greens from MOST nutritious to LEAST.

Kale: This nutrition powerhouse offers everything you want in a leafy green. It's an excellent source of vitamins A, C, K, and calcium. It also supplies folate and potassium.

Spinach: This superfood is packed with vitamins A, C, E, K, B2, B6, folate, magnesium, manganese, betaine, iron, calcium, potassium, folic acid, copper, protein, phosphorus, zinc, niacin, selenium and omega-3 fatty acids. Because heat reduces the green's oxalate content, freeing up its dietary calcium, "cooked spinach gives you more nutrition than raw," says Nussinow.

Collard greens: Similar in nutrition to kale but they have a heartier and chewier texture and a stronger cabbage-like taste. Collards can be used as a wrapper instead of tortillas or bread and yield only 20 calories per serving.

Turnip greens: "If you buy turnips with the tops on, you get two vegetables in one," Nussinow tells WebMD. Loaded with vitamins A, C, K, and calcium, they're also packed with fiber and lutein, a caretenoid concentrated in the retinas of your eyes and a necessary component of normal vision.

Swiss chard: Has a beet-like taste and soft texture that's perfect for sauteeing. Good source of vitamins A, C, lutein, potassium, and fiber. It is also rich in minerals and protein.

Broccoli: With just 25 calories per serving, broccoli is rich in vitamin C and is also a good source of vitamin A, potassium, and folate.

Romaine Lettuce: A familiar sight in salad bowls, romaine is high in vitamin A and offers some folate.

Cabbage: Although paler in color than other leafy greens, this cruciferous vegetable is a great source of cancer-fighting compounds and vitamin C.

Iceberg Lettuce: This bland-tasting head lettuce is mostly water, but it's the country's most popular leafy green. However, it's last on our list for its health benefits. "It's not devoid of all nutrition, but it's pretty close," Nussinow tells WebMD.

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