Bladder wrack
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| Fucus vesiculosus L. |
Bladder wrack (Fucus vesiculosus L.) is a seaweed found on the coasts of the North Sea, the western Baltic Sea, and the Atlantic and Pacific Oceans. It was the original source of iodine, discovered in 1811, and was used extensively to treat goitre, a swelling of the thyroid gland related to iodine deficiency. In the 1860s, it was claimed that bladder wrack, as a thyroid stimulant, could counter obesity by increasing the metabolic rate and, since then, it has been featured in numerous weight-loss remedies.
Bladder wrack (sometimes spelled bladderwrack) is also known by the names black tang, rockweed, bladder Fucus, seawrack, sea oak, black tany, cut weed, and rock wrack.
[edit] Description
Fucus vesiculosus is a very variable alga. It can grow to 100 cm or more and is easily recognised by the small nitrogen gas filled vesicles which occur in pairs on either side of a central midrib running along the centre of the strap-like frond. Ascophyllum nodosum also has air vesicles, however they are not in pairs but in series along a frond which is not flattened and without a midrib. Both are common species on most shores of the British Isles.
[edit] Medical and nutritional uses
A common food in Japan, it is used as an additive and flavoring in various food products in Europe. Bladder wrack is commonly found as a component of kelp tablets or powders used as nutritional supplements. It is sometimes loosely called kelp, but that term technically refers to a different seaweed.
Primary chemical constituents of this plant include mucilage, algin, mannitol, beta-carotene, zeaxanthin, iodine, bromine, potassium, volatile oils, and many other minerals. The main use of bladder wrack (and other types of seaweed) in herbal medicine is as a source of iodine, an essential nutrient for the thyroid gland. Bladder wrack has proved most useful in the treatment of underactive thyroid glands (hypothyroidism) and goitre. Through the regulation of thyroid function, there is an improvement in all the associated symptoms. Where obesity is associated with thyroid trouble, this herb may be very helpful in reducing the excess weight. It has a reputation in helping the relief of rheumatism and rheumatoid arthritis, both used internally and as an external application upon inflamed joints. A chemical constituent of bladder wrack called alginic acid swells upon contact with water; when taken orally, it forms a type of "seal" at the top of the stomach, and for this reason is used in several over-the-counter preparations for heartburn. The same constituent gives bladder wrack laxative properties as well. Other proposed uses of bladder wrack include treating atherosclerosis and strengthening immunity, although there is no scientific evidence at present that it works for these purposes.
Bladder wrack should not be used in cases of hyperthyroidism or cardiac problems, or during pregnancy and lactation. Excessive dosage (many times the recommended dosage) may lead to hyperthyroidism, tremor, increased pulse rate and elevated blood pressure.
