Herbs have been accepted as part of traditional Asian medicines for thousands of years and interest in herbal remedies has grown in western countries as research into this area identifies active components in herbs. Figures in Asia are lacking however a NBC News/Prevention magazine poll in the United States found that as many as 16 million Americans use herbal products. A study conducted in Singapore last year by Temasek Polytechnic School of Business found that more than half of those surveyed claimed to purchase dietary supplements including herbal products.

Just how effective are these products and how do we know they are safe to take? Food Facts Asia takes a look at what the science says about some of the more popular herbal remedies. In most cases, the jury is still out and no firm conclusions or recommendations can be drawn.

Often taken as a tea, chamomile may aid digestion. This herb is a member of the daisy family so people who are allergic to other members of this family including ragweed, asters or chrysanthemums need to be careful.

This is a popular remedy in those hoping to boost their immune systems and fight off a cold. Some studies have reported that Echinacea may help in fighting upper respiratory tract infections however the studies are not conclusive and further research is needed. Echinacea is usually sold as an extract or in tablet form. It is not recommended during pregnancy or for people with tuberculosis or an autoimmune disease such as lupus or multiple sclerosis.

The seeds and fruits of the Gingko tree have been used as medicines in China since 2800 B.C. Some studies suggest that gingko biloba may improve circulation, memory and mental functioning, especially in older people. It has also been studied for use as an anti-depressant. A 52-week, multi-centre study of 309 men and women diagnosed with uncomplicated dementia (memory loss) found that gingko biloba improved cognitive performance and social functioning in some patients. (The Journal
of the American Medical Association, 278:1327,1997). The study has been criticised however due to high a drop-out rate and a worsening of the dementia in one third of the patients. More data is needed before any conclusions can be made.

St. John's Wort has been used for over a thousand years in the treatment of several conditions including kidney and lung disorders. It has been widely used for treating anxiety, depression and sleep disorders. An analysis of 23 clinical studies published in the British Medical Journal last year concluded that St. Johns Wort extracts may provide some benefit in people suffering from depression. The reviewers cautioned however that further studies are needed and data on the most effective dosage and long-term safety is required. Recent studies show that St. John's Wort can reduce blood levels, and therefore the effectiveness, of other medications taken at the same time.

Herbal products are neither food nor drugs and in many cases they are loosely regulated or even unregulated. Many countries lack quality controls for herbal products and dietary supplements and products can be marketed with no proof of their effectiveness or safety.

In the United States, herbal products are regulated under the Dietary Supplement and Health Act. This Act allows manufacturers to make unproven claims about the product provided they do not state that it cures or treats a disease. Vague claims such as "improves immunity" or "slows aging" are allowed without the need for scientific evidence to support the claims.

When using herbal products, consumers need to take care to judge products on the data available and the quality of that data. Many people are misled into believing that if a product is "natural" it is safe. Yet these products contain active ingredients that have similar effects to drugs and medicines and similar levels of care need to be taken when consuming them.

As with other forms of self-medication, herbal remedies may hide a serious underlying medical condition. For example, depression can be caused by a number of serious illnesses including heart disease and thyroid disorders. For this reason, it is recommended that people wishing to take herbal supplements seek the advice of their medical practitioner and always notify their doctors if they are taking herbal preparations.

Herbs to avoid