Nearly three quarters of us use some form of complementary medicines, including vitamins, minerals, herbs, aromatherapy and homeopathic products. But are these as safe as we think?

The word ‘natural’ is advertised across packages of food, supplements, herbs and even detergents. That’s because when we read ‘natural’ we tend to think pure, unadulterated, and harmless. But this may not always be the case.

Reviews of studies on widely available complementary medicines have found that while some have been well-studied and found to be effective, many have not and evidence for their effectiveness is often lacking or of poor quality.

Health risks

Like pharmaceutical drugs, complementary medicines can cause harm, even if they are used correctly. The risks include:

Indirect harm: relying on complementary therapies alone could delay your diagnosis and medical treatment. In the case of serious illnesses, such as cancer, a delay can lead to serious complications or death.

Side effects: some supplements and herbs can cause unwanted and potentially dangerous side effects. For example, the herb feverfew can cause uterine contractions and possible miscarriage in pregnant women.

Drug interactions: some complementary medicines can interact with over-the-counter or prescription drugs. These include evening primose oil, ginkgo, glucosamine, hawthorn, and St John’s wort.

When you’re prescribed a medication, or start taking a complementary medicine when you’re on other medication, it’s wise to let your doctor and pharmacist know everything else you are taking. This is particularly important if you are undergoing surgery, as certain herbal medicines and supplements can interfere with anaesthesia and other medication, as well as with blood clotting and blood pressure.

Risky ingredients: some complementary medicines may not contain what they claim. Last year a major research project lead by researchers from the University of Adelaide and Western Australia’s Murdoch University and Curtin University found many supplements and herbal medicines available to consumers were not exactly what they claimed to be.

More than two thirds of the products tested either had ingredients missing or contained foreign material, including DNA traces of frog, shrew, reindeer, goat and dog. In a small number of cases, herbal supplements contained levels of lead, arsenic, cadmium or mercury that exceeded the safe maximum dose, while others contained undeclared drugs, including an anti-inflammatory pharmaceutical.

While the traces of heavy metals and pharmaceutical drugs are concerning and potentially dangerous, the researchers suggested contamination from commonly domesticated animals could be inadvertent and due to manufacturing deficiencies or transportation.