The study, conducted by Jennifer Di Noia of William Paterson University, looked at 17 important nutrients naturally occuring in food (fiber, protein, potassium, Vitamin A, B12, D) and calculated how much of those nutrients were found in a 100-calorie serving. The results are interesting.
Watercress ranks as the most nutrient-rich vegetable, while other leafy greens like chard, chicory and lettuce rank well. Turnips, sweet potatoes and grapefruits performed worse. That said, any quantity of vegetables is better than the alternative.