Dark green leafy vegetables benefit your body by purifying your blood, preventing cancer, improving circulation, strengthening your immune system, promoting healthy intestinal flora, improving liver, gall bladder and kidney function, and clearing congestion in the lungs according to Institute for Integrative (IIN) Nutrition. Leafy green vegetables include broccoli, bok choy, napa cabbage, kale, collards, watercress, mustard greens, arugula, lettuce, mesclun, spinach, Swiss chard and beet greens. The easiest way to increase leafy veggies is to eat a salad every day, just include this with one of your meals or in place of one of your meals. You can also steam, saute, or boil greens. Boiling these vegetables helps them plump up but make sure you only boil them for a minute, otherwise the greens lose valuable nutrients.