Thujone is a known poison and the FDA (food and drug adminstration in the U.S) have restricted it’s use, but is this an overreaction?
Tansy, mugwort, wormwood and yarrow have all been used in food and drink for centuries can they really be that poisonous? As with most science the answer is not black and white, but shades in between. Whether or not you decide to use food containing thujone is entirely your choice, but being armed with a little more information might help you make up your mind.
I spoke to Khaled M. Abass, Phd a European Registered Toxicologist from the Research Unit of Biomedicine, University of Oulu, Finland. Who told me that the, “Committee of Herbal Medicinal Products gives two different maximum daily intakes, 3 and 5 mg of thujone/person (70 kg). However, Occurrences of alpha- and beta-thujone in plants depend on plants, batch, seasons, and origins”. This makes it rather difficult to judge how much is a safe level to use when foraging for any plant that contains thujone. So, I asked him what he thought about collecting and eating or drinking wild plants that contain thujone and more specifically in tansy and he said , “It is difficult to estimate thujone in tansy or other mixture unless the content of thujone is shown in batch”. Which isn’t really much help for the forager.
Needless to say there have been some animal studies that might help us come up with an anwser especially as one of them states that humans have, “claimed to be at least as sensitive as experimental animals to the central nervous system (CNS) effects of thujone”. I’m not really sure how many rats and mice were asked, but lets just have a bit of faith in the scientific approach. One study gave stupidly high measured brain concentrations (Hold et al, 2000) and within a few minutes almost all of the animals tested died. I’m never sure about the validity of these studies, they seem a bit pointless really you could go as far as saying feeding mice water can kill them as we got a 200g mouse and gave it one cubic tonne of water. It blew up. It tells us nothing.
Luckily, that wasn’t the only study. Another (Margaria, 1963) gave four groups of 10 female and 10 male rats various doses (0mg, 5mg, 10mg and 20mg) of thujone, (per kg of weight), six times a week for fourteen weeks. There was no observable effect reported in the 10mg does for males and 5mg for females. At the highest does there were convulsions in nine females and six males and in the 10mg group only one female convulsed and this was in day 38. Further, there were three deaths in the female rats and one male death. The take home from both studies is moderation. But again it is hard to know what this moderate level should be.