Just 21 calories' worth of asparagus (about six medium spears) supplies 5 percent or more of the recommended intake of 25 nutrients (nine vitamins, nine minerals, and seven essential amino acids). Asparagus contains nearly as much insoluble fiber as celery, promoting healthy gastrointestinal function, and four times as much soluble fiber, the kind that lowers cholesterol. Asparagus is also the most abundant dietary source of glutathione, the main antioxidant in human cells. In addition, a University of Florida study endorsed asparagus as an excellent source of folate, a B vitamin that reduces blood levels of the amino acid homocysteine, helping to prevent heart disease. Serve fresh asparagus the day you buy it, or wrap the stalk bottoms in a damp paper towel and refrigerate the spears until you're ready to cook.