Asparagus – using this delicious vegetable as a natural diuretic

by Christina Paulson, Aachen

It's the asparagus season! These popular, tasty shoots are ready to be harvested from the sandy soil. White or green, they are delicious and healthy. According to tradition, the pale stalks were known as «the food of the gods» in Ancient Egypt and reserved for the pharaohs. The oldest known written reference to asparagus in Europe comes from the well known Greek doctor Hippocrates (460 to 370 BC). He mentions, surprisingly, its astringent quality – probably referring to the roots, although its diuretic qualities were also known to him. The thin-stalked lesser asparagus (Asparagus acutifolius) is native to the eastern Mediterranean where it grows on warm, stony, damp ground. It tastes slightly bitter and stronger than the European cultivar Asparagus officinalis. The genus name «asparagus» comes from the Greek word for «young shoot».

Asparagus shoots were esteemed by prosperous Romans even two centuries before Christ as a delicacy and an aphrodisiac. The first instructions for growing asparagus come from Marcus Porcius Cato (234 to 149 BC) in «De Agricultura«. In 1AD, the Roman military doctor Dioscorides praised asparagus as a remedy for bladder, spleen and liver disease in his book «De materia medica«. He recommended wearing an amulet of asparagus as a contraceptive.

It remains unclear exactly who brought asparagus to Europe, the Romans, the Benedictine monks or returning crusaders. In any case, it was being used in Germany as a medicinal herb by the late Middle Ages and grown in monastery gardens.

Written in the first half of the15th century, the «Leipziger Drogenkunde» recommends asparagus for spleen, liver, dysuria including urine retention, stomach and intestine pain. By the end of the 18th century it was used as a remedy for «blood cleansing» and for rheumatic complaints. Only the wealthy would have been able to afford this medicine, however: for an effective daily dose, one pound of asparagus was required and it was expensive even in those days. The low calorie content would have made it unsuitable for anyone doing hard physical work.

The first indications of large-scale asparagus cultivation in Germany come from courts in Germany, England and France. Its use was certainly encouraged by the aphrodisiac effects ascribed to it. The German doctor and botanist Jakobus Theodorus Tabernaemontanus (1520 to 1590) suggested in his herbal of 1588 to take equal amounts of asparagus root and pepper («pfefferkümmel») and pound together and take «darvon eins quintleins schwer» with some fine wine to bring ‘life to the marriage bed'.

Cultivation makes the difference

The drawings and paintings of the beginning of the 17th century suggest that predominately green asparagus was being cultivated. The colour is not indicative of variety however, it is dependent on growing methods. As long as the finger-thick sprouts grow underground they remain white. Asparagus growers harvest the shoots before they break through the surface of the soil. They can judge the right moment when the smoothed surface of the sand banks starts to crack. The anthocyane content is responsible for the violet colour which often appears at the tips. As soon as the tips break the surface, chlorophyll is formed and the stalks turn green. Asparagus which is to be harvested green is therefore grown in flat beds. Asparagus under cultivation needs a light, slightly humus, porous, sandy soil.

Green asparagus is richer in minerals and nutrients and tastes stronger than the white type. It contains magnesium, potassium, vitamin C and folic acid in particular. It is much appreciated by the figure and health conscious due to its low calorie content and high proportion of fibre and water (94%). It is also an invaluable vegetable for diabetics.

Here are some nutritional content figures for white, peeled asparagus:

• Content per 100 g
• Energy: 17 kcal/71 kJ
• Water: 94 g
• Carbohydrate: 1.9 g
• Protein: 1.9 g
• Fat: 0.1 g
• Fibre: 1.8 g
• Vitamin C: 21.0 mg
• Folic acid: 0.1 mg
• Potassium: 207 mg
• Magnesium: 20 mg

Diuretic saponins

The saponins and potassium in the woody rootstock are responsible for the diuretic effect of asparagus. The roots (Asparagi radix, Asparage rhizoma) are harvested, dried and pulverised then added to diuretic teas and medicines such as Asparagus-P^®. It is prescribed for irrigation therapy in treating inflammation of the urinary tract, cystitis and to prevent kidney stones. The daily dose is 45 to 60 gm of dried drug. As this dose is scarcely achievable with teas, the root is mixed with stronger diuretic drugs such as nettle or parsley root. Patients with urinary tract inflammation should drink 2 to 3 litres of water daily as well.

Not for gout patients

The saponins in asparagus can irritate the kidney: patients with inflammatory kidney disease or oedema resulting from heart or kidney disease should not use asparagus preparations. Those with chronic kidney disease should also keep their intake of asparagus to a minimum. The same applies to people with raised uric acid levels, in particular gout patients. In every 100gm of asparagus there is approximately 25 mg of purines which are broken down into uric acid in the body.

Vanillin is partly responsible for the typical taste of asparagus. The somewhat unpleasant odour which the urine aquires after asparagus has been eaten is caused by the volatile sulphur compound methyl mercaptan, a by-product of the sulphur-containing aspartic acid.

The asparagus season finishes on the 24th of June; by then the shoots can have grown up to a meter tall, and are allowed to grow out. They take on the appearance of small trees with fine, thin twigs. The above-ground parts ensure that the rhizomes can store reserves for the new shoots the following year.

The small, single-sex flowers appear in July. They grow up to 7 mm in length, are bell-shaped and whitish-green. In autumn, the female flowers develop brick red berries which contain mildly poisonous steroid saponins. Only the ingestion of very large quantities would lead to sickness and vomiting. Some highly sensitive people do have a contact allergy to asparagus, e.g. while paring it. This is caused by the sulphur compounds. Other allergic reactions besides urticaria can be hay fever and asthma.

The author's address:

Dr. Christina Paulson
Kantstraße 26
52078 Aachen