Complementary medicines: are they effective?

Published in Medicinewise Living

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complementary medicines

Less is known about the effectiveness, side effects and interactions of complementary medicines. Image: Melinda Fawver /

Complementary medicines are popular in Australia. They can be used to ‘complement’ medicines prescribed by a health professional or, in some cases, may be used as an alternative to conventional treatments.

Vitamins, herbal medicines and mineral supplements are widely available through pharmacies, supermarkets, online retailers, and complementary health practitioners (e.g. naturopaths). 

Some people report benefits from taking these medicines, but are they really effective? And, is there any evidence to show that they actually help you?

There is some research into certain complementary medicines that shows there may be a benefit in using them. However, there is a lack of evidence from good clinical trials to support the effects of many complementary medicines.

Here are a few points to consider when deciding whether to try a complementary medicine.

Complementary medicines are medicines too

Complementary medicines, while often less powerful than prescription medicines are medicines and still need to be used with care.

Like all medicines, they have side effects, interactions and, in the worst case scenario, they can potentially be harmful. This is why it is important that you tell your health professional about all the medicines you or anyone in your care is taking.

When you're sick with cold or flu, it may be tempting to try complementary medicines to help speed-up your recovery. Three medicines that are commonly promoted as helping treat or prevent cold and flu are echinacea, zinc, and vitamin C.

How is the medicine made and what is it made from?

There can be a large variation in how a complementary medicine is made and what it is made from. For example, echinacea  preparations (often used to treat colds and flu):

  • are available in various forms (tablets or liquids)
  • are available in various strengths
  • can be made from different parts of the echinacea plant (e.g. the stems, leaves and/or roots)
  • may be made in different ways (e.g. as the dried herb, extracts of the plant juices in alcohol or fresh juice pressed from the plant)
  • sometimes contain other ingredients (e.g. other types of plant extract).

This means that when buying a complementary medicine, it is difficult to know which form and strength to buy, how much of it to take, and what side effects might you experience.

This is not the same for prescription and pharmacy medicines, which have strict manufacturing, testing and marketing rules and regulations.

Is there evidence that the medicine works?

Prescription and pharmacy medicines sold in Australia have to undergo extensive clinical research and testing.

Complementary medicines do not have to be proven to work in the same way as prescription and pharmacy medicines do. They undergo less testing in general, so less is known about their effectiveness, side effects and interactions.

In other words, a complementary medicine might not do what it is claimed to do and, at worst, it could possibly do you harm.

Here’s the low-down on what the research has shown so far about these complementary medicines for colds and flu.

What is it? Echinacea is a flowering plant that is often used to help treat or prevent colds or flu and is also thought to assist in wound healing.
Will it cure my cold? It is not known whether echinacea really can prevent or treat colds or flu (influenza). This is because most echinacea preparations have not been tested in reliable clinical trials. Therefore, there is no good information on how much echinacea you would need to take, how long you should take it for, or which form is the most effective (dried, fresh juice or extracts in alcohol).
Side effects, interactions and other things you should know Echinacea preparations are highly variable. It is made in various forms and strengths and can be made from different parts of the plant. These variations make its usefulness and side effects very difficult to measure. There’s also limited information about the safety of echinacea preparations. One clinical trial in children with colds found that the children taking echinacea experienced more rashes than children taking a placebo (an inactive substance).
What is it? Zinc is a mineral found naturally in some foods. It is used by the body for a variety of functions, including supporting the immune system and wound healing.
Will it cure my cold? Clinical trials have shown that zinc might shorten the length of your cold if you are generally healthy and you take zinc within 24 hours of your symptoms appearing. But these studies have not established exactly how much zinc you need to take, what form is the most effective (lozenges or syrup), or for how long you should take it.
Side effects, interactions and other things you should know Zinc lozenges can cause side effects like nausea or a bad taste in the mouth. Zinc can interact with some prescription medicines and other minerals. Tetracycline and quinolones (types of antibiotic) may work less effectively if you are also taking zinc. Taking calcium supplements at the same time as zinc can interfere with how your body absorbs the zinc.
Vitamin C
What is it? Vitamin C is found in fresh fruit, especially citrus fruits, and some vegetables. It helps to keep your skin, bones and connective tissue healthy, and is involved in wound healing.
Will it cure my cold? Vitamin C is commonly used to treat or prevent colds, but vitamin C supplements have not been shown to prevent colds or to give reliable effects in treating the symptoms of a cold in clinical trials. It is suggested that vitamin C supplements may help people with pneumonia, but more research is needed to prove this.
Side effects, interactions and other things you should know No clinical trials have yet tested the effect of vitamin C on colds in children.

Tell your health professional about all the medicines you — or anyone in your care — are taking, including prescription, over-the-counter and complementary medicines (herbal or natural medicines and vitamin and mineral supplements).

This is because all medicines, including herbal and natural medicines, can cause side effects and may interact with other medicines. The benefits and risks of herbal and natural medicines may not have been tested.