Rather than prescription or over-the-counter drugs, many of us use herbal medicines to relieve pain or treat illnesses. But a new study published in the journal Fungal Biology claims some herbal medicines are contaminated with toxic molds at levels that pose harm to human health.

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High levels of toxic molds were identified among 30 samples of plants commonly used for herbal medicines. These molds could cause serious illness in humans.

Herbal medicine is described as the use of plants to treat medical conditions. According to the research team, from the University of Peshawar in Pakistan, around 64% of people use herbal medicines.

Study author Samina Ashiq says that because these medicines are natural, there is a “common misconception” that they are safe, but this may not be the case. The plants may be subject to contamination by molds that produce mycotoxins.

At high levels, these mycotoxins can trigger adverse effects in humans. They have been linked to liver cancer, kidney damage, reproductive disorders and immune system suppression.

Despite the risks herbal medicines may pose, however, they are not well regulated. The Food and Drug Administration (FDA) deem herbal medicines as food products, therefore they are not subject to the same testing, manufacturing and labeling standards as prescription and over-the-counter drugs.

This is the same for most countries worldwide, including Pakistan, where the majority of people use herbal medicines. “It’s common to use medicinal plants in our country and to buy from local markets and shops,” says Ashiq.

For their study, the team set out to determine the levels of toxic mold found in 30 samples of commonly used herbal medicines.

They identified mold in 90% of the samples, and in 70% of the samples, the mold levels exceeded acceptable levels.

Next, the team investigated whether the molds found in these samples produced mycotoxins by growing them.

They found that 31% of the molds produced harmful mycotoxins – 19% of which produced aflatoxins (linked to liver cancer) and 12% of which produced ochratoxin A (harmful to the liver and kidneys).

Harmful molds were identified in around 43% of the samples. Aflatoxins were present in around 30% of the samples, while 26% were contaminated with ochratoxin A. Licorice root, opium poppy and Indian rennet were the most highly contaminated plants.

The researchers explain that plants used for herbal medicines can become contaminated during any stage of production, including growth, handling, collection, transportation and storage. These plants are commonly sold on market stalls in many countries, the researchers note, which are not renowned for good hygiene.

According to Ashiq, their findings indicate that stronger regulation needs to be in place for herbal medicines:

There is a real public health concern due to the lack of effective surveillance of the quality, safety and efficacy of these medicinal plants. It’s time for regulators to step in and set limits to protect people who want to use herbal medicines like these.

By setting limits to fungal contamination of these plants, Pakistan and other countries would be better able to export to places that do have controls in place. Hygienic processing and sale of medicinal plants is essential to protect people, and also if the economy is to benefit from the booming herbal medicine industry.”

Earlier this year, Medical News Today reported on a study claiming a Chinese herbal medicine is just as effective as a medication called methotrexate against arthritis.