Safe by perception, risky in practice? What vitamin B6 and turmeric teach us about complementary medicines

Complementary medicines – vitamins, minerals, probiotics, and herbal products – are widely used in everyday self-care. They are readily available over the counter, which can create a false sense of safety. But many people take them daily, for months or years, sometimes alongside prescription medicines. The assumption that “natural means safe”, combined with limited discussion with health professionals, can make potential side effects easy to miss, sometimes until they become serious.

Take vitamin B6, for example. Vitamin B6 is an essential nutrient, but sustained high intake can damage peripheral nerves. Early symptoms include tingling, burning, or numbness in the hands or feet, which can eventually progress to balance or walking problems.

Overdosing is easier than one might expect. Individuals may, often unknowingly, take multiple vitamin B6–containing products. One Australian report found vitamin B6 in more than 1,500 over-the-counter products, and around 80% contain amounts well above the recommended daily intake. Labels may also list vitamin B6 under different chemical names, making it easy for consumers to stack doses without recognising that it is the same ingredient.

Adverse-event reporting is an even bigger issue: In our study, 12% reported experiencing side effects, yet none had submitted an official report. Many only considered reporting serious reactions and were unsure how to do so. This is a common problem in pharmacovigilance – warning signals emerge slowly when people do not recognise a reaction as product-related, and when reporting pathways are unclear or inconvenient.

Herbal products can be risky too. For example, culinary turmeric is generally safe, but concentrated turmeric supplements, often marketed for inflammation or joint pain, have been linked to rare, sometimes severe liver injury. In 2023, the TGA issued a safety alert after receiving 18 reports of turmeric-related liver problems. Some cases were severe, and one case resulted in death. Similar concerns appear in clinical reports. In Italy, a regional safety review of seven cases linked liver injury to concentrated turmeric supplements. In the United States, the Drug-Induced Liver Injury Network documented 10 well-investigated turmeric-linked cases between 2011 and 2022, including one death, and new clinical reports continue to emerge.

The key message is not that complementary medicines are dangerous, but that dose and formulation matter. A spoonful of spice in food is not the same exposure as multiple high-dose capsules taken daily, sometimes paired with ingredients intended to increase absorption. When those differences are not obvious, people can shift from “food” to “medicine-like dosing” without realising that the risk profile may change too.

What can help? Clearer labelling and consistent naming can reduce accidental stacking. Routine conversations between consumers and healthcare providers are critical. Reading labels carefully, stopping products that seem linked to new symptoms, and reporting suspected side effects can transform individual experiences into early warning signals that prevent harm for others.

This article was written with contributions from Renly Lim (Adelaide University), Barbora de Courten (RMIT University), Ayman Allahham (RMIT University), and Wejdan Shahin (RMIT University).