Asparagus

Scientific Name(s): Asparagus officinale L. Family: Liliaceae

Common Name(s): Garden asparagus

Clinical Overview

Uses of Asparagus

The stalks commonly are eaten. Roots, seeds, and extracts of these have been used as a treatment for various ills and as a diuretic.

Asparagus Dosing

There is no recent clinical evidence to guide dosage of asparagus products.

Contraindications

Contraindications have not yet been identified.

Pregnancy/Lactation

Generally recognized as safe or used as food. Avoid dosages above those found in food because safety and efficacy are unproven.

Asparagus Interactions

None well documented.

Asparagus Adverse Reactions

None known except for pungent odor in urine of almost half of those who eat it.

Toxicology

There are no reports of serious toxicity from the ingestion of asparagus or its extracts.

Botany

Asparagus is a dioecious perennial herb with scale-like leaves and an erect, much-branched stem that grows to a height of up to 3 meters. Asparagus is native to Europe and Asia and is cultivated widely. The part used as a vegetable consists of the aerial stems, or spears, arising from rhizomes. The fleshy roots and, to a lesser degree, the seeds have been used for medicinal purposes.

History

Asparagus spears are used widely as a vegetable and frequently are blanched before use. Extracts of the seeds and roots have been used in alcoholic beverages, with the maximum levels averaging 16 ppm. The seeds have been used in coffee substitutes, diuretic preparations, laxatives, remedies for neuritis and rheumatism, to relieve toothache, to stimulate hair growth, and as cancer treatments. Chinese medicine has used them to treat parasitic diseases. Extracts are said to have served as contraceptives. Home remedies have employed the topical application of preparations containing the shoots and extracts to cleanse the face and dry acneform lesions.

Chemistry

Asparagus roots contain inulin and at least eight fructo-oligosaccharides. Two glycoside bitter principles, officinalisins I and II, were isolated from dried roots in yields of 0.12% and 0.075%, respectively. Other root components are beta-sitosterol, steroidal glycosides (asparagosides A to I, in order of increasing polarity), and asparagusic acid. The shoots have several sulfur-containing acids (asparagusic, dihydroasparagusic and S-acetyldihydroasparagusic); alpha-amino-dimethyl-gamma-butyrothetin, a glycoside bitter principle different from those in roots; flavonoids (rutin, quercetin and kaempferol); as well as asparagine, arginine, tyrosine, sarsasapogenin, beta-sitosterol, succinic acid, and sugars. Asparagusic acid, and its derivatives, are plant growth inhibitors; they also are nematocidal (imparting resistance to several important plant parasite nematodes). 1

Asparagus seeds contain large quantities of sodium hydroxide-soluble polysaccharides consisting of linear chains of beta-glucose and beta-mannose in a 1:1 ratio, 1 to 4 linked to alpha-galactose as a terminal group. 1 Seeds also contain 3 ribosome-inactivating proteins, in concentrations of 8 to 400 mg/100 g of starting material. These proteins, with molecular weights of approximately 30,000, have alkaline isoelectric points and inhibit protein synthesis by rabbit reticulocyte lysate. 2 Asparagus stalks contain folate and the folate conjugases asparagusate dehydrogenase I and II, as well as lipoyl dehydrogenase. Folate levels can be measured accurately only after inactivation of the conjugases. 3 Stalks also may contain residues of permethrin, an insecticide often applied to protect asparagus during growth. These residues peak approximately 3 days after insecticide treatment and then decline by approximately 85% by the seventh day. 4 Other herbicides applied during the growth of asparagus have been detected in commercial stock. 5

Asparagus Uses and Pharmacology

Asparagus roots have been used in diuretic preparations, but no data are available to substantiate this pharmacologic effect.

Research reveals no animal or clinical data regarding the use of asparagus as a diuretic.

Related species of asparagus have demonstrated antiviral activity in vitro. 6 Asparagus juice has demonstrated in vitro antimutagenic activity 7 and cytotoxic saponins have been found in the plant. 8

Dosage

There is no recent clinical evidence to guide dosage of asparagus products.

Pregnancy/Lactation

Generally recognized as safe or used as food. Avoid dosages above those found in food because safety and efficacy are unproven. 9

Interactions

None well documented.

Adverse Reactions

Ingestion of asparagus spears produces a characteristic pungent odor in the urine of some individuals within a few hours. 10 According to one report, the odor is produced by a combination of 6 sulfur-containing alkyl compounds: Methanethiol, dimethyl sulfide, dimethyl disulfide, bis-(methylthio)methane, dimethyl sulfoxide, and dimethyl sulfone. Possible precursors of these compounds are S-methylmethionine and asparagusic acid. 11 Other researchers attribute the urine odor to S-methylthioacrylate and S-methyl 3-(methylthio)thiopropionate. 12

In one study, 43% of 800 volunteers had urine odor following asparagus ingestion. Production of the odor appears to be an autosomal dominant genetic trait that is evident throughout life. 13 A study of 307 volunteers found that 10% had the ability to smell high dilutions of urine from asparagus-fed individuals, suggesting that the ability to smell asparagus-tainted urine is also a specific trait. 14 A study of 19 volunteers confirmed that only some people have the ability to produce or detect the odor. 15 This may suggest a genetic composition to these traits.

Toxicology

There are no reports of serious toxicity from the ingestion of asparagus or its extracts. There is one report of botulism poisoning following the ingestion of improperly home-preserved asparagus. 16

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