Asparagus are dioecious perennial low-growing plants with narrow needle-like leaves and tuberous roots. Dioecious means male and female flowers are borne separately on each plant, and thus need cross-pollination.
Originating in the Eastern Mediterranean region, and cultivated for over 2,000 years, it spread to Egypt, and Northern Africa and North America. Today, commercial asparagus is grown in the U.S., Mexico, Peru, France, Spain, and other Mediterranean countries.
The purplish green, white, or purple spears are actually shoots from underground crowns. It takes about 2-3 years for the plants to yield harvestable shoots, but once they do they can live for 20 years or longer. Male plants yield more shoots and live longer than female plants. Frost tolerant and a cool season crop, they need temperature ranges of 16-24 degrees Celcius in the growing season for spear production, and lower temperatures at dormancy. The green and purple varieties are more nutritious than the white cultivar because of chlorophyll and anthocyanins that gives the shoots a "fruitier" flavor and a higher antioxidant content. Only about 20 species of asparagus are edible, but about 300 cultivars have been identified.
Health Benefits
Asparagus contains: 19 antioxidants, 10 cardioprotective compounds, 1 anti-platelet, 1 anti-thrombogenic, and 17 hypocholesterolemic agents making it a powerful heart healthy vegetable. Rutin prevents platelets from clumping together,and supports healthy capillaries. Chromium and Zinc lower triglyceride levels, while antioxidant vitamins, minerals, and phytosterols prevent oxidation of blood fats, adhesion of oxidized materials in arterial walls, and improve cholesterol ratio.
Folate reduce serum homocysteine levels. Homocysteine weakens blood vessel walls and interferes with collagen synthesis. About 20% -40% of people with heart disease have elevated serum homocysteine levels.
Folate also prevents neural tube defects. As part of coenzymes (tetrahydrofolate and dihydrofolate) which are critical in DNA synthesis; cells do not divide and multiply properly. During pregnancy, folate deficiency has been associated with spina bifida. Folate comes from the Latin word "folium" meaning "foliage" because it abounds in leafy green vegetables. Folate deficiency is one of the most common vitamin deficiencies worldwide.
Inulin in asparagus supports Lactobacillus and Bifidobacteria - gut friendly microorganisms. Humans cannot digest inulin - a polysaccharide - but these bacteria can. In return, they prevent harmful bacteria from establishing themselves in our intestinal tract.
Nutrition Information and Preparation
Asparagus is an excellent source of vitamin K, folate, and vitamins C and A. It is a very good source of tryptophan (an amino acid), vitamins B1, B2, B3, and B6, magnesium, dietary fiber, copper, phosphorus, protein, and potassium. It is also a good source of glutathione, a protein antioxidant and detoxifying agent.
Glutathione binds fat-soluble poisons and transforms them into water-soluble substances that can be excreted in urine.
Delicious steamed, lightly boiled, sauteed, stir-fried, and cooked with other vegetables or by itself, asparagus is an epicurean delight. Steaming or using small amounts of cooking liquid is the best cooking method as it preserves asparagus' delicate flavour and prevents water-soluble vitamins from leaching out.
References
Gopalakarishnantr, TR "Perenial Crops" Vegetable Crops New India Publishing 2007; p.323
"What is Glutathione?" Ontario Asparagus Growing Association Newsletter May 1, 2004
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