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Detected plant toxins in herbal tea


Photo: Erling Fløistad

NIBIO is performing an annual monitoring programme of plant toxins in food commissioned by the Norwegian Food Safety Authority. In 2021, certain plant toxins were detected in 13 herbal tea products. To reduce the possible health risk, the Norwegian Food Safety Authority recommends limiting your intake of herbal tea.

Many plants produce plant toxins which are a natural protection against insects and other herbivores. The natural toxin content in plants used for food is generally low, but certain weeds can contain many strong toxins. If weeds are included in the harvesting of food plants, the harmful plant toxins can end up in our food. In 2021 NIBIO analysed 30 samples to survey selected plant toxins on behalf of the Norwegian Food Safety Authority.

20 different types of herbal tea were analysed for a group of plant toxins called pyrrolizidine alkaloids. These can be harmful to the liver and carcinogenic when ingested over time. Varying levels of pyrrolizidine alkaloids were detected in 13 of the products of nursing tea, rooibos tea, chamomile tea and peppermint tea.

To reduce the potential health risk, the Norwegian Food Safety Authority recommend limiting the consumption of these types of teas and varying between different products. This applies particularly to pregnant and breastfeeding women.

The results from the Norwegian Food Safety Authority’s monitoring programme are used to assess the risk to human health from ingesting food. Updated data is important to be able to manage this risk through regulation, warnings and information for consumers.

“Further monitoring is important to see whether the new maximum levels of the plant toxins lead to fewer detections and lower levels of such plant toxins in food products,” explains researcher Marit Almvik at NIBIO. Tea grown and harvested in accordance with good agricultural practice and constituted from certified herbs with high purity could help reduce contamination with plant toxins from weeds.