Health Canada reports there have been three cases in the country of liver damage associated with the use of black cohosh, which resulted in death, and one published case in the US. The federal agency says the advisory is only "precautionary" while it reviews the safety and effectiveness of the herb.
The US, with its post-market regulation of herbals, is notably missing from the growing list of countries which have flagged black cohosh. While the recent warnings in other countries could bring a further slump in sales of the ingredient.
According to a report from market analyst Datamonitor, sales for black cohosh experienced a decline of 42 percent in the United Kingdom between 2003 and 2005, owing to "negative publicity surrounding the functional qualities of the herb" which led manufacturers not to use it.
Health Canada's advisory means manufacturers will have to notify consumers of the potential risk.
"With respect to labelling, in accordance with Part 5 of the Regulations, all labels must list any risks associated with the product's use," Health Canada spokesperson Nathalie Lalonde told NutraIngredients-USA.com in a written statement.
Black cohosh (referred to by Health Canada as actaea racemosa or cimicifuga racemosa)is a member of the buttercup family, and is a perennial plant native to North America.
It has been traditionally used to reduce menopausal symptoms such as hot flashes and has been a popular alternative to hormone replacement therapy (HRT).
In its advisory Health Canada qualifies that "case reports of liver damage are rare and the link between black cohosh and liver toxicity is unclear".
"Consumers should discontinue the use of products containing black cohosh and consult a physician if they have unusual fatigue, weakness, loss of appetite, or if they develop symptoms suggestive of liver injury such as yellowing of the skin or whites of the eyes, dark urine or abdominal pain."
Unlike the recent announcements in the UK and Australia, Health Canada does not require products carrying black cohosh to carry warning labels.
In February, Australia's Therapeutics Goods Administration (TGA) required all over-the-counter and alternative medicines containing black cohosh to carry a warning for the potential risk for the liver. And in July, the United Kingdom's Medicines and Healthcare Products Regulatory Agency (MHRA) announced it will also introduce potential liver damage warning labels for black cohosh products. The announcement coincided with a public safety statement from the European Medicines Agency (EMEA).