For many decades now, unsaturated pyrrolizidine alkaloids have been known to be potentially harmful, causing specific types of liver and lung damage, and also being carcinogenic. However the question has long been “do the amounts in key medicinal plants warrant concern?”. Many regulatory authorities around the world think so, with some of these plants being restricted for medicinal usage. This research project set out to determine the level of evidence for harm from some of these plants.
The research project was funded by the National Institute of Medical Herbalists in the United Kingdom, as a way of producing an unbiased and evidence-based assessment of the knowledge around the potential of human harm from the medicinal use of Symphytum officinale (Comfrey), Tussilago farfara (Coltsfoot), and Borago officinalis (Borage). As a result they went outside the UK, to Australia, and asked Australian herbalist and researcher Dr Sue Evans to put together a team to try to answer the question.
I was honoured to be approached to be a part of this research team, particularly given that I am still early in my research career, and the rest of the team are all highly experienced. The team consisted of Dr Catharine Avila, Dr Sue Evans, Dr Jason Hawrelak, Dr Ses Salmond, and myself. All of us are experienced herbalists, with different areas of expertise which we have been able to bring to the project. In fact, Cathy Avila was one of my teachers and external clinical supervisors back in 1991-1992, so it was wonderful to be working with her again!
In short, the answer to the question is still not 100% clear. However what was clear was that in many instances the case reports of harm from these plants, upon which many of the regulatory decisions have been based, were lacking in substance. There were many published cases where misidentification or substitution of the herb with other plants appeared to have occurred, where proper botanical identification of the herb was absent, and where rigorous assessment of causality was lacking.
If you’re interested, you can read the full paper here:
Avila, C., Breakspear, I., Hawrelak, J., Salmond, S., & Evans, S. (2020). A systematic review and quality assessment of case reports of adverse events for borage (Borago officinalis), coltsfoot (Tussilago farfara) and comfrey (Symphytum officinale). Fitoterapia, 142, 104519. https://doi.org/10.1016/j.fitote.2020.104519