Water makes up 93% of asparagus's composition. Asparagus is low in food energy and very low in sodium. It is a good source of vitamin B6, calcium, magnesium, and zinc, and a very good source of dietary fibre, protein, beta-carotene, vitamin C, vitamin E, vitamin K, thiamin, riboflavin, rutin, niacin, folic acid, iron, phosphorus, potassium, copper, manganese, and selenium, as well as chromium, a trace mineral that regulates the ability of insulin to transport glucose from the bloodstream into cells. The amino acid asparagine gets its name from asparagus, as the asparagus plant is relatively rich in this compound.