Recently, reports of the toxic effects
of pyrrolizidine alkaloids in comfrey have led some herbalists to be wary of using it internally.
It is shown repeatedly that the general public is largely unaware of important consumer health protection topics, such as
pyrrolizidine alkaloids in teas and honey, or wrongly classifies them as being of no concern, such as food hygiene in private households.
In contrast, only around 13 percent of respondents have heard of the natural
contaminants pyrrolizidine alkaloids (PAs) in honey or tea — and only roughly one in three of those who have heard of PAs believe these substances pose a significant health risk.
The main concern with butterbur however is that if not prepared properly, it can be contaminated
with pyrrolizidine alkaloids, which are carcinogenic; they can also cause liver and kidney damage.
The raw herb as well as teas, extracts, and capsules made from the raw herb should not be used because they contain substances
called pyrrolizidine alkaloids that can be toxic to the liver and kidneys and have been linked to cancer.
In contrast,
pyrrolizidine alkaloids (PAs) in tea or honey (13 %) and arsenic in rice and rice products (26 %) as relatively new consumer protection topics are only known to a minority of respondents.
«With regards to the warnings that comfrey can cause cancer and liver disease, most herbal practitioners point out that those results were from studies that isolated
the pyrrolizidine alkaloids and fed or injected them into animal subjects in doses far higher than any typical usage of comfrey leaf, and that comfrey leaf has been regularly ingested by thousands of people around the world without reported ill effects.»
Contraindications: The plant (but not the oil) contains small amounts of
pyrrolizidine alkaloids that may cause toxicity in the liver, and Borage should never be taken in large doses (many times the recommended amount) or for a long period of time.
It is possible to remove
the pyrrolizidine alkaloids from butterbur products.