THE POISON GARDEN website      Arum maculatum berries on a Cannabis leaf 


This free script provided by JavaScript Kit

Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Tuesday 8th October 2013

I said, yesterday, that I was working on a piece about what a ‘fatal dose’ really means but another story caught my eye so I’m broadening it to a more general look at some of the things that are wrong but still widely believed.

In part, people seem to cling to discredited beliefs because they want to continue to believe in the subject concerned and are, therefore, dismissive of work that undermines the basis for the belief. But, there is also the question of beliefs that have not been widely discredited because very few people are aware that the basis has been challenged.

I’ll start with e-cigarettes. The active ingredient of plants in the Nicotiana genus, tobacco, is nicotine, widely accepted as a highly addictive substance making quitting very difficult. E-cigarettes have been adopted by people who want to be able to get a nicotine ‘hit’ in places where smoking is not permitted, by people who want to avoid the harms inherent in smoking tobacco but are happy with their nicotine addiction and by those who want to use e-cigarettes as a pathway to breaking their addiction to nicotine completely. There are also claims that previous non-smokers are taking up e-cigarettes.

Nicotiana genus, tobacco

I’ve read some of the many articles about e-cigarettes but I can’t say I’ve reached a settled conclusion about whether they should be encouraged, regulated or banned. But what interested me was that discussions about the desirability, or otherwise, of giving people access to liquids high in nicotine has led to a consideration of what is a lethal dose and how that lethal dose was determined.

The accepted lethal dose of nicotine is said to be 60mg for adults. I’ve always had a problem with that number because lethal doses are measured per kg and 60mg obviously gives very different concentrations per kg for adults whose weight can range from less than 50kg to well over 100kg. I’ve just accepted that ‘small amounts’ can be fatal.

Part of the argument against e-cigs is the small dose of nicotine that could prove fatal. Now, a researcher in Austria, Bernd Mayer, has looked into the origin of the 60mg claim and written an editorial for the journal Archives of Toxicology setting out what he found.

He first looked at the LD50 figures determined in animals and found that these were far higher than the implied LD50 resulting from a 60mg dose for a 75kg adult. Then he looked at a variety of case reports of deaths due to nicotine poisoning and found that they all involved far higher doses. He estimated that the lethal dose might be 20 times higher than the 60mg figure suggests.

Having concluded that the 60mg figure did not stand up, he went looking for its source and found, mostly, that it was one of those numbers that everybody knows, i.e. it had been accepted for so long that it was no longer questioned and cited references to it did not lead to an explanation of its source.

Finally, he found a reference in a book, in German, from 1906 that said that it was difficult to determine the true fatal dose but that it was certainly not more than 60mg. In part this figure was based on some self-experimentation by researchers who, obviously, took a non-lethal dose and recorded the experience. It was those non-lethal doses that led to the estimation of the fatal dose.

Actaea spicata, baneberry

This is similar to the work done by Mrs Alice E. Bacon, in 1903, on the effects of eating Actaea spicata rubra, red baneberry. Mrs Bacon tried ‘a small dose, followed by ‘double the dose’ and then a further doubling of the dose. From the escalation of the seriousness of the poisoning she experienced, she concluded that another doubling, to 12 berries, would be fatal. The Actaea spicata very rarely produces poisonings so there is nothing surprising about the fact that no-one has undertaken modern experimentation to check that claim. Nicotine, however, is a much more widely available poison so it is surprising that almost no work has been done to examine the veracity of the 60mg claim.

It is too early to know if Mayer’s editorial will lead to a widespread re-assessment of the toxic effects of nicotine but it certainly hasn’t had an immediate impact. This morning the BBC report on today’s vote in the EU Parliament on what to do about e-cigarettes spoke about nicotine being a fatal poison in very small amounts so it hasn’t immediately entered the mainstream.

The other accepted claim that was in my mind resulted from the pre-publicity for a new TV programme ‘Trust Me I’m a Doctor’ This programme is, apparently, going to look at some of the things people believe about health that are not supported by evidence. The notion that drinking 2l of water a day is essential is going to the one of the topics. (It isn’t, in case you didn’t know.)

That made me wonder if the series will look at the related subject of caffeine being a diuretic. Many of those who espouse the false idea that you should drink 2l of water a day will tell you that it must be water because drinks with caffeine, like coffee and tea, are diuretics and you will end up more dehydrated that you started.

Here’s what I wrote in October 2011 on this subject.

‘…many people will tell you, as indisputable fact, that coffee is a diuretic. Even doctors, when suggesting an increase of fluid intake, will often say not alcohol and not coffee or tea because caffeine is a diuretic.

‘But, that perception of caffeine comes from a 1928 study involving three subjects whose urination patterns were studied, for a few hours only, before and after drinking coffee. There were no controls i.e. no-one was asked to drink the same amount of liquid with no caffeine present so concluding that the need to wee after drinking a quantity of coffee was due to the caffeine is about as unscientific as it gets.’

There are other examples of dubious information achieving wide acceptance. I’ve written before about Mrs Grieve’s claim that Atropa belladonna, deadly nightshade, berries are ‘insanely sweet’ and how that gets repeated when it is simply untrue.

Rather than blindly accepting ‘facts’ about poisons, it is always useful to consider how those facts arose and if later work has confirmed or debunked the information.

Submit a Comment

You can send comments via the contact page but please be sure to say what blog entry you are commenting on.

Follow @thepoisongarden on Twitter

Full Entries


Tuesday 25th October 2016 Saturday 20th August 2016 Sunday 6th March 2016 Wednesday 3rd February 2016


Saturday 28th November 2015 Friday 27th November 2015 Monday 17th August 2015 Wednesday 15th July 2015 Friday 26th June 2015 Thursday 25th June 2015 Thursday 30th April 2015 Wednesday 29th April 2015 Wednesday 11th March 2015 Tuesday 3rd March 2015 Saturday 28th February 2015 Sunday 22nd February 2015

November 2014


Monday 24th November 2014 Saturday 8th November 2014

October 2014

September 2014

Wednesday 24th September 2014 Monday 1st September 2014

August 2014

Tuesday 26th August 2014 Saturday 16th August 2014 Tuesday 5th August 2014 Friday 1st August 2014

July 2014

Sunday 27th July 2014 Wednesday 23rd July 2014 Sunday 13th July 2014 Sunday 6th July 2014 Tuesday 1st July 2014

June 2014

Wednesday 25th June 2014 Tuesday 24th June 2014 Sunday 22nd June 2014 Monday 9th June 2014 Wednesday 4th June 2014

May 2014

Monday 26th May 2014 Sunday 18th May 2014 Wednesday 14th May 2014

April 2014

Sunday 13th April 2014 Saturday 5th April 2014 Thursday 3rd April 2014 Tuesday 1st April 2014

March 2014

Monday 31st March 2014 Tuesday 25th March 2014 Friday 21st March 2014 Monday 17th March 2014 Sunday 16th March 2014 Tuesday 11th March 2014 Thursday 6th March 2014 Wednesday 5th March 2014 Saturday 1st March 2014

February 2014

Thursday 27th February 2014 Monday 24th February 2014 Wednesday 19th February 2014 Monday 17th February 2014 Thursday 13th February 2014 Monday 4th February 2014 Monday 3rd February 2014 Saturday 1st February 2014

January 2014

Thursday 28th January 2014 Thursday 23rd January 2014 Friday 17th January 2014 Wednesday 15th January 2014 Monday 13th January 2014 Thursday 9th January 2014 Tuesday 7th January 2014 Wednesday 1st January 2014

December 2013

Monday 23rd December 2013 Friday 20th December 2013 Tuesday 17th December 2013 Friday 14th December 2013 Thursday 12th December 2013 Sunday 8th December 2013 Wednesday 4th December 2013 Sunday 1st December 2013

November 2013

Friday 29th November 2013 Wednesday 27th November 2013 Tuesday 26th November 2013 Friday 22nd November 2013 Monday 18th November 2013 Friday 15th November 2013 Thursday 14th November 2013 Sunday 10th November 2013 Thursday 7th November 2013 Wednesday 6th November 2013 Friday 1st November 2013

October 2013

Thursday 31st October 2013 Sunday 27th October 2013 Wednesday 23rd October 2013 Monday 21st October 2013 Friday 18th October 2013 Friday 11th October 2013 Wednesday 9th October 2013 Tuesday 8th October 2013 Monday 7th October 2013 Tuesday 1st October 2013

September 2013

Monday 30th September 2013 Saturday 28th September 2013 Friday 27th September 2013 Monday 23rd September 2013 Sunday 15th September 2013 Monday 9th September 2013 Sunday 8th September 2013 Tuesday 3rd September 2013 Sunday 1st September 2013

August 2013

Tuesday 27th August 2013 Sunday 25th August 2013 Monday 19th August 2013 Friday 16th August 2013 Tuesday 13th August 2013 Friday 9th August 2013 Friday 2nd August 2013 Thursday 1st August 2013

July 2013

Saturday 27th July 2013 Sunday 21st July 2013 Wednesday 17th July 2013 Monday 15th July 2013 Saturday 13th July 2013 Friday 12th July 2013 Thursday 11th July 2013 Wednesday 10th July 2013 Tuesday 9th July 2013 Saturday 6th July 2013

June 2013

Friday 28th June 2013 Tuesday 25th June 2013 Friday 21st June 2013 Thursday 20th June 2013 Wednesday 19th June 2013 Saturday 15th June 2013 Sunday 9th June 2013 Saturday 8th June 2013 Saturday 1st June 2013

May 2013April 2013 March 2013 February 2013 January 2013 December 2012 November 2012 October 2012 September 2012 August 2012 July 2012 blog June 2012 blog May 2012 blog April 2012 blog March 2012 blog February 2012 blog January 2012 blog December 2011 blog November 2011 blog October 2011 blog September 2011 blog August 2011 blog July 2011 blog June 2011 blog


The POISON GARDEN website is not connected with Alnwick Garden Enterprises Ltd and/or The Alnwick Garden Trust.