Asparagus has dietary fibre, vitamin A, and C. It is an excellent source of the B vitamin folate. It is a diuretic, and also provides inulin, an excellent prebiotic which will nourish the bacteria of the intestinal flora, improving digestion, and giving you a flat stomach. Choose firm, bright-green stalks. The tips should be purplish and tightly closed. Use fresh. Canned asparagus have less than half the nutrients found in freshly cooked spears.