Asparagus

The fleshy green spears of asparagus are both succulent and tender and have been considered a delicacy since ancient times. This highly prized vegetable arrives with the coming of spring. In California the first crops are picked as early as February, however, their season generally is considered to run from April through May. The growing season in the Midwest and East extends through July.

Asparagus is a perennial, an almost leafless member of the lily family. The spears we buy in the store are actually the shoots from an underground crown. It takes up to 3 years for crowns to develop enough to begin producing shoots, but once they do, they can produce for up to 20 years.

This chart graphically details the %DV that a serving of Asparagus provides for each of the nutrients of which it is a good, very good, or excellent source according to our Food Rating System. Additional information about the amount of these nutrients provided by Asparagus can be found in the Food Rating System Chart. A link that takes you to the In-Depth Nutritional Profile for Asparagus, featuring information over 80 nutrients, can be found under the Food Rating System Chart.

• Health Benefits
• Description
• History
• How to Select and Store
• How to Enjoy
• Individual Concerns
• Nutritional Profile
• References

Health Benefits

Heart Health

Folate is essential for a healthy cardiovascular system. Folate is involved in the methylation cycle, a biochemical event in which a methyl group--one atom of carbon and three atoms of hydrogen--is transferred from one molecule to another. Methylation reactions are the body's biochemical "spark plugs" in a wide variety of very important reactions. For example, methylation is crucial for the proper transcription of DNA, and transforms norepinephrine into adrenaline, and serotonin into melatonin. When the methylation cycle flows smoothly, the amino acid methionine is transformed into homocysteine, which is quickly converted into cysteine, and then back into methionine. Folate (along with vitamins B6 and B12) is necessary for the conversion of homocysteine into cysteine. When folate levels are low, blood levels of homocysteine rise, a situation that significantly increases the risk for heart disease. Homocysteine promotes atherosclerosis by reducing the integrity of blood vessel walls and by interfering with the formation of collagen (the main protein in connective tissue). Elevations in homocysteine are found in approximately 20-40% of patients with heart disease, and it is estimated that consumption of 400 mcg of folate daily would reduce the number of heart attacks suffered by Americans each year by 10%. Just one serving of asparagus supplies almost 66% of the daily recommended intake of folate.

A Natural Diuretic

Asparagus is a very good source of potassium (288 mg per cup) and quite low in sodium (19.8 mg per cup. Its mineral profile, combined with an active amino acid in asparagus, asparagine, gives asparagus a diuretic effect. Although some popular articles on asparagine link this amino acid to the distinct urinary odor that can follow along after consumption of asparagus, research studies suggest that this odor stems from a variety of sulfur-containing compounds (discussed in detail under the Individual Concerns section below). Historically, asparagus has been used to treat problems involving swelling, such as arthritis and rheumatism, and may also be useful for PMS-related water retention.

Food for Healthy Gut Flora

Asparagus contains a special kind of carbohydrate called inulin that we don't digest, but the health-promoting friendly bacteria in our large intestine, such as Bifidobacteria and Lactobacilli, do. When our diet contains good amounts of inulin, the growth and activity of these friendly bacteria increase. And when populations of health-promoting bacteria are large, it is much more difficult for unfriendly bacteria to gain a foothold in our intestinal tract.

A Birth Defect Fighter

Especially if you're thinking about becoming pregnant or are in the early stages of pregnancy, make asparagus a frequent addition to your meals. A cup of asparagus supplies approximately 263 mcg of folate, a B-vitamin essential for proper cellular division because it is necessary in DNA synthesis. Without folate, the fetus' nervous system cells do not divide properly. Inadequate folate during pregnancy has been linked to several birth defects, including neural tube defects like spina bifida. Despite folate's wide availability in food (it's name comes from the Latin word folium, meaning "foliage," because it's found in green leafy vegetables), folate deficiency is the most common vitamin deficiency in the world.

Description

Asparagus is a perennial garden plant belonging to the Lily family (Liliaceae). While approximately 300 varieties of asparagus have been noted, only 20 are edible.

Asparagus, its fleshy spears topped with bud-like compact heads, is often thought of as a luxury vegetable, prized for its succulent taste and tender texture. It is harvested in the spring when it is 6 to 8 inches tall. While the most common variety of asparagus is green in color, two other edible varieties are available. White asparagus, with its more delicate flavor and tender texture, is grown underground to inhibit its development of chlorophyll content, therefore creating its distinctive white coloring. It is generally found canned, although you may find it fresh in some select gourmet shops, and it is generally more expensive than the green variety since its production is more labor intensive. The other edible variety of asparagus is purple in color. It is much smaller than the green or white variety (usually just 2 to 3 inches tall) and features a fruitier flavor. It also provides benefits from phytonutrients called anthocyanins that give it its purple color. With prolonged cooking, the purple color may disappear.

History

Asparagus has been prized as an epicurean delight and for its medicinal properties for almost 2000 years. Originating in the eastern Mediterrean region, it has become naturalized throughout much of the world. It was thought to be cultivated in ancient Egypt with varieties discovered in northern and southern Africa. Falling into relative obscurity in the Middle Ages, asparagus was "rediscovered" and popularized in the 18th century by Louis XIV. Today, asparagus is cultivated in most subtropical and temperate parts of the world with the majority of commercially available asparagus grown in United States, Mexico, Peru, France, Spain and other Mediterranean countries.

How to Select and Store

Asparagus stalks should be rounded, and neither fat nor twisted. Look for firm, thin stems with deep green or purplish closed tips. The cut ends should not be too woody, although a little woodiness at the base prevents the stalk from drying out. Once trimmed and cooked, asparagus loses about half its total weight. Occasionally, white asparagus that has a milder flavor than green asparagus is available. White asparagus is buried under soil to block chlorophyll production, thus resulting in a white plant. Some markets also offer purple asparagus, which has a fruitier flavor than green or white asparagus.

Use asparagus within a day or two after purchasing for best flavor. Store in the refrigerator with the ends wrapped in a damp paper towel, and be sure to place the asparagus in the back of the refrigerator away from any light, since folate is destroyed by exposure to air, heat or light.

How to Enjoy

For some of our favorite recipes, click Recipes.

Tips for Preparing Asparagus:

Asparagus

Tips for Preparing Asparagus:

Asparagus can be served hot or cold. While it is not necessary to peel asparagus, you should cut off the fibrous base before cooking. Wash it under cold water to remove any sand or soil residues.

You can tie asparagus stalks in a bundle to steam them, as this will make it easier to remove the stalks once cooked. If you find you enjoy this unusual vegetable so much that you become a true aficiando, you might consider purchasing one of the special tall, narrow steamers available that allow asparagus to be cooked to perfection-the tips are steamed while the thick stalks are cooked thoroughly in the boiling water. Avoid cooking asparagus in iron pots as the tannins in the asparagus can react with the iron and cause the stalks to become discolored. If your recipe calls for cold asparagus, plunge the stalks into cold water immediately after cooking, then remove them quickly; letting them soak too long can cause them to become soggy.

A Few Quick Serving Ideas:

For a delectable hors d'oeuvre, roast asparagus along with other vegetables such as pattypan squash, Portobello mushrooms, and beets.

Steamed asparagus served with light lemon vinaigrette makes a delightfully refreshing salad.

Toss freshly cooked pasta with asparagus, olive oil and your favorite pasta spices. We especially enjoy thyme, tarragon and rosemary.

Chopped asparagus make a flavorful and colorful addition to omelets.

Healthy sauté asparagus with garlic, shiitake mushrooms and tofu or chicken.

Individual Concerns

Contrary to popular belief, persons who experience a strong odor coming from their urine after eating asparagus are not in any danger from eating this vegetable. A variety of different chemicals-all breakdown products of asparagus-can be found in the urine in connection with the "asparagus smell". These chemicals generally fall within a chemical category called mercaptans (or to use a more modern term, thiols). They include dimethyl sulfide, dimethyl disulfide, dimethyl sulfoxide, bis-(methylthio)methane, S-methyl thioacrylate, S-methyl-3-(metyhylthio)thiopropionate and dimethyl sulphone. Different people form different amounts of these compounds after eating asparagus, and many people cannot smell the odor, even when they produce the compounds.

Asparagus and Purines

Asparagus contains naturally-occurring substances called purines. Purines are commonly found in plants, animals, and humans. In some individuals who are susceptible to purine-related problems, excessive intake of these substances can cause health problems. Since purines can be broken down to form uric acid, excess accumulation of purines in the body can lead to excess accumulation of uric acid. The health condition called "gout" and the formation of kidney stones from uric acid are two examples of uric acid-related problems that can be related to excessive intake of purine-containing foods. For this reason, individuals with kidney problems or gout may want to limit or avoid intake of purine-containing foods such as asparagus. For more on this subject, please see "What are purines and in which foods are they found?"

Nutritional Profile

Asparagus is an excellent source of vitamin K, the B vitamin folate, vitamin C, vitamin A. Asparagus is a very good source of numerous B vitamins - including vitamin B1, B2, B3 and B6 - as well as dietary fiber, manganese, copper, phosphorus, potassium and protein.

For an in-depth nutritional profile click here: Asparagus.

In-Depth Nutritional Profile

In addition to the nutrients highlighted in our ratings chart, an in-depth nutritional profile for Asparagus is also available. This profile includes information on a full array of nutrients, including carbohydrates, sugar, soluble and insoluble fiber, sodium, vitamins, minerals, fatty acids, amino acids and more.

Introduction to Food Rating System Chart

In order to better help you identify foods that feature a high concentration of nutrients for the calories they contain, we created a Food Rating System. This system allows us to highlight the foods that are especially rich in particular nutrients. The following chart shows the nutrients for which this food is either an excellent, very good, or good source (below the chart you will find a table that explains these qualifications). If a nutrient is not listed in the chart, it does not necessarily mean that the food doesn't contain it. It simply means that the nutrient is not provided in a sufficient amount or concentration to meet our rating criteria. (To view this food's in-depth nutritional profile that includes values for dozens of nutrients - not just the ones rated as excellent, very good, or good - please use the link below the chart.) To read this chart accurately, you'll need to glance up in the top left corner where you will find the name of the food and the serving size we used to calculate the food's nutrient composition. This serving size will tell you how much of the food you need to eat to obtain the amount of nutrients found in the chart. Now, returning to the chart itself, you can look next to the nutrient name in order to find the nutrient amount it offers, the percent Daily Value (DV%) that this amount represents, the nutrient density that we calculated for this food and nutrient, and the rating we established in our rating system. For most of our nutrient ratings, we adopted the government standards for food labeling that are found in the U.S. Food and Drug Administration's "Reference Values for Nutrition Labeling." Read more background information and details of our rating system.

Asparagus, boiled 1.00 cup 180.00 grams 43.20 calories Nutrient Amount DV (%) Nutrient Density World's Healthiest Foods Rating vitamin K 91.80 mcg 114.8 47.8 excellent folate 262.80 mcg 65.7 27.4 excellent vitamin C 19.44 mg 32.4 13.5 excellent vitamin A 970.20 IU 19.4 8.1 excellent tryptophan 0.05 g 15.6 6.5 very good vitamin B1 (thiamin) 0.22 mg 14.7 6.1 very good vitamin B2 (riboflavin) 0.23 mg 13.5 5.6 very good manganese 0.27 mg 13.5 5.6 very good dietary fiber 2.88 g 11.5 4.8 very good vitamin B6 (pyridoxine) 0.22 mg 11.0 4.6 very good copper 0.20 mg 10.0 4.2 very good vitamin B3 (niacin) 1.95 mg 9.8 4.1 very good phosphorus 97.20 mg 9.7 4.1 very good protein 4.66 g 9.3 3.9 very good potassium 288.00 mg 8.2 3.4 very good iron 1.31 mg 7.3 3.0 good zinc 0.76 mg 5.1 2.1 good magnesium 18.00 mg 4.5 1.9 good selenium 3.06 mcg 4.4 1.8 good calcium 36.00 mg 3.6 1.5 good World's Healthiest Foods Rating Rule excellent DV>=75% OR Density>=7.6 AND DV>=10% very good DV>=50% OR Density>=3.4 AND DV>=5% good DV>=25% OR Density>=1.5 AND DV>=2.5%

In-Depth Nutritional Profile for Asparagus

References

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• FDA News. Folic acid to fortify US food products to prevent birth defects. FDA News. Feb 29 1996 1996.
• Glueck, CJ, et al. Evidence that homocysteine is an independent risk factor. Am J Cardiology(1995):132-6 1995.
• Margen S and the Editor, Univ of California at Berkley Wellness Letter. The Wellness Encyclopedia of food and nutrition. New York: Health Letter Associates 1992 1992.
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• National Food Safety Database. National Food Safety Database. http://www.foodsafety.ufl.edu.
• Rieder M. Prevention of neural tube defects with periconceptional folic acid. Clin Perinatol, 21: 483-502 1994 1994.
• Suitor CW. Food folate vs. synthetic folic acid: a comparison. J Am Diet Assoc 1999;99:285 1999.
• Wood, Rebecca. The Whole Foods Encyclopedia. New York, NY: Prentice-Hall Press; 1988 1988. PMID:15220.
• Yaeger S and the Editors of Prevention Health Books. The Doctor's Book of Food Remedies. St. Martin's Press 1998 1998.

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