Cliona Ni Mhurchu and Andrew Jull: Clinical trials essential for all health remedies

COMMENT

The important issue surrounding therapeutic products is not whether a product falls into the category of complementary or mainstream, but whether there is good evidence to support its safe and effective use.

While as individuals we all have the right to use whatever remedies we wish within the law, we are also entitled to know whether therapeutic products can safely achieve what they claim.

Unfortunately, the debate has become polarised, but the evidence suggests that, as a whole, complementary products are the same as mainstream products - some are harmful, some have no effect and some are beneficial.

A uniform, independent process to sort out which is which and to protect the public is the main rationale for a joint New Zealand-Australian therapeutic products regulatory agency.

It does not follow that vitamins and herbs are safe products simply because they are natural. In fact, some have been proved to have serious side-effects. Beta-carotene, a form of vitamin A, has been shown in several large clinical trials to increase the risk of cancer in smokers.

The Food and Drug Administration in the United States has proposed warning labels on all products containing the dietary aid ma huang (ephedra) as a result of evidence that it has caused at least a dozen deaths.

Other commonly consumed supplements such as st john's wort and ginkgo have been shown to have serious interactions with life-saving medications such as aspirin.

K4, a supplement sold as a treatment for prostate problems, may be another example, given the 13 cases of liver damage associated with use of the product reported to the New Zealand Centre for Adverse Reactions Monitoring.

With conventional medicines, good-quality data is collected on their safety and side-effects. Research in women taking the third-generation contraceptive pill showed a slight increase in the risk of blood clots, but the level of risk was so small that data were required from many thousands of women to detect it.

With dietary supplements the lack of regulation means that side-effects from these products are less likely to be monitored and reported. Therefore, the true number of people who have had side-effects from dietary supplements is simply not available.

A related safety issue is that without regulations the composition and quality of dietary supplements is uncertain. In several instances, herbal products, when tested, have been found to contain prescription medicines or toxic substances.

There have been several examples lately of alternative health products marketed (implicitly or explicitly) for health conditions, ranging from depression to cold prevention, that have been shown to have no efficacy, but have side-effects.

Vitamin C supplements are commonly taken to prevent or treat colds, but research shows that vitamin C does not prevent colds, and might reduce symptoms for only about half a day. Echinacea and evening primrose oil are other examples of products that rigorous clinical trials have now shown to have little or no benefits.

Conversely, there are some natural health products that should be used much more widely because the evidence of their efficacy is good. Omega-3 fatty acids (fish oils) are a good example of a natural dietary supplement that has been shown to reduce risk of heart disease.

The evidence is also promising for products such as ginger (in the treatment of nausea) and st john's wort (in the treatment of mild to moderate depression). Clinical trials also offer convincing evidence that therapies such as hypnosis and relaxation techniques can alleviate anxiety, panic disorders and insomnia, while tai chi can help the elderly to overcome their fear of falls.

Contrary to many opinions, it is usually impossible for individuals to determine the benefits or side-effects of therapeutic products unless their effects are substantial and immediate.

Most of our health problems are long term; they wax and wane because of a wide variety of factors, and the health products we consume are just one of these factors. Sorting out what works, therefore, needs evidence, not anecdote.

That is why there must be clinical trials - a group of people should have the treatment and their response compared to a group that does not have the treatment. This evidence, in turn, should be reviewed and summarised by an independent body.

Globally, 10,000 researchers are involved voluntarily in the Cochrane Collaboration, a worldwide initiative to summarise the evidence for different treatments, both complementary and mainstream . People wanting to know whether a treatment works can start their search at its website Informed Health Online.

* Cliona Ni Mhurchu and Andrew Jull are research fellows in Auckland University's clinical trials research unit. They are responding to Ron Law's view that there is no evidence of dietary supplements having caused serious illness and death.