Important warning: please note that all medicines, including herbal medicines, should be taken only on the advice of a qualified practioner. Many beneficial treatements do not work in particular circumstances and may be antagonistic. For all medicines a particular dose and course of treatment must be observed; it should be noted that more of a good treatment is not necessarily better. You should not treat yourself on the basis of any information given here.

In Europe and North America, many claims have been made for the effectiveness of seaweeds on human health. It has been suggested, amongst other things, that seaweeds have curative powers for tuberculosis, arthritis, colds and influenza, worm infestations, and may even improve one's attractiveness to the opposite sex. Digenea (Ceramiales; Rhodophycota) produces an effective vermifugal agent (kainic acid). Recently, aqueous extracts from two red algae belonging to the family Dumontiaceae have been found to inhibit the herpes simplex virus but no tests have been carried out on humans. Carrageenans have been patented as anti-viral agents. Many of the reported medicinal effects of marine algae have not been substantiated. Corallina is being used used in bone-replacement therapy. Stein & Borden (1984) provide a more extensive review.

Some kelps may have polysaccharides that apparently reduce the incidence of breast cancer.

Four seaweeds are commonly used in Chinese medicine:

• Saccharina japonica and Ecklonia kurome as sources of kunbu (Saccharina- formerly Laminaria is sometimes called haidai, to distinguish it from Ecklonia and other sources)
• Sargassum, a brown algae, as the source of haizao; Sargassum is a large genus and several species seem to be in use.
• Porphyra, a red algae, as the source of zicai

Saccharina and Sargassum have been used in China for the treatment of cancer. Inhibition of cancerous tumours in animals seems to be caused by long-chained polysaccharides. Dry Saccharina stipes have long been used in obstetrics to dilate the cervix and were known as "Laminaria tents" (Stein & Borden, 1984); the dry stipe slowly takes up water and expands; such stipes are also used in China for the insertion of intrauterine devices.

According to Chinese medicine, seaweeds have a salty taste that is an indication that the material can disperse phlegm accumulation, particularly as it forms soft masses, include goitre, the thyroid swelling that indicates severe iodine deficiency. The following are descriptions of seaweeds from Oriental Materia Medica:

Kunbu (Saccharina and Ecklonia) (Kombu in Japan)

• Essence and Flavor: Salty, Cold
• Channel Entered: Liver, Stomach, Kidney
• Actions: Softens hardness, disperses accumulation, resolves phlegm, cleanses heat
• Applications: Scrofula, goiter, tumor, edema, accumulation, testicular pain and swelling
  
  

Haizao (Sargassum)

(Hiziki in Japan; generally Sargassum fusiforme, but other sargassi are used in China)

• Essence and Flavor: Bitter, Salty, Cold
• Channel Entered: Liver, Stomach, Kidney
• Actions: Disperses accumulated phlegm, disperses goiter and tumor, delivers water, cleanses heat
• Applications: Scrofula, goitre, tumor, edema, testicular pain and swelling
  
  

Zicai (Porphyra) (Nori in Japan)

• Essence and Flavor: Sweet, Salty, Cold
• Channel Entered: Lung
• Actions: Resolves phlegm, softens hardness, dispels heat, promotes diuresis
• Applications: Goiter, beriberi (leg swelling), edema, urinary infection, sore throat

The descriptions for kunbu and haizao are quite similar. Yang Yifan wrote about the differences between these commonly used seaweeds: Haizao and Kunbu are salty and cold, and enter the liver, lung, and kidney meridians. Both can clear heat, transform phlegm, soften hardness, and dissipate nodules. They can also promote urination and reduce edema. In clinical practice, they are often used together to treat nodules such as goiter and scrofula. There are some differences between the two seaweeds. Haizao is stronger in transforming phlegm and dissipating nodules, and it is more suitable for treating goiter and scrofula. Kunbu is stronger in softening hardness and reducing congealed blood; it is more suitable for treating liver-spleen enlargement, liver cirrhosis, and tumors. One of the best known formulas with the seaweeds is Haizao Yuhu Tang, or the Sargassum Decoction for the Jade Flask. This formula of 12 ingredients includes Sargassum, Ecklonia, and Saccharina. It was used to treat a condition of goitre which was so severe it made the throat look like a large flask. However, these seaweeds have been adopted into formulas for treating other soft swellings, including ovarian cysts, breast lumps, lymph node swellings, lipomas, and fat accumulation from simple obesity (modified from http://www.itmonline.org/arts/seaweed.htm).