Australasian Science: Australia's authority on science since 1938

Toxins in Herbal Medicines “Can Harm Our Health”

By Staff

People who take unregulated complementary medicines are at a higher risk of being contaminated by heavy metals such as arsenic, cadmium, mercury and lead, the Cleanup 2015 conference in Melbourne has been told.

“Some of these heavy metals are accumulated by herbal plants as they grow in contaminated soil. Some are added into the medicine directly,” said Dr Shankar Bolan of the Cooperative Research Centre for Contamination Assessment and Remediation of the Environment. “One example is the addition of arsenic, mercury and lead into the Ayurvedic medicine Rasayan Shastra due to a belief that these metals can improve your health or potency.”

While Australia has strict regulations to stop these medicines from being sold, people are still buying them through the internet or from overseas.

Bolan has developed a technique that can quickly determine the levels of heavy metals in these medicines, as well as their bioavailability – the portion available to affect human health. “These complementary medicines we take are not completely broken down by our body,” he said. “The amount that stays and accumulates to affect the body over time is what we need to watch out for.”

After analysing six herbal and six Ayurvedic medicines, Bolan found that the Ayurvedic medicines contained higher levels of arsenic, cadmium, mercury and lead than the herbal ones. “The bioavailability of these heavy metals was also higher in Ayurvedic medicines,” he said. “This suggests that medicines that have heavy metals added to them may be more toxic to humans, compared to those that are made from contaminated plants.”

Bolan also investigated the “worst case scenario” – taking the maximum daily dose as instructed on the packages. “For herbal medicines, the amount of heavy metals absorbed by the body is still within the safe threshold as determined by the World Health Organisation. However, taking the maximum dose for some Ayurvedic medicines is likely to result in levels of mercury, lead and cadmium that exceed the safe threshold.”

Bolan said that these complementary medicines are generally very well regulated in Australia. “It’s those that ‘escape the net’ that we need to be concerned with, and they are easily bought from websites or over the counter overseas.”