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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Monday 18th July 2011

At this time of year our garden is full of birds. Actually, I should have said that our garden is always full of birds. We put food out all year round and have plenty of large shrubs to give them shelter. I sometimes think I spend more on food for the birds than for us but I’ve never dared check in case that’s true.

Today, I saw another of those discussions about how to get birds into the garden and, as usual, someone said that you shouldn’t give birds whole peanuts in the spring because they will give them to their young and choke them. I can understand people saying this when the RSPB says it on its website but I can’t help wondering if anyone has ever thought it through.

First of all, it’s not just new-borns who would choke if they tried to eat a whole peanut. I doubt if any of the birds seen in UK gardens could swallow a whole peanut without harming themselves. So, if peanuts are dangerous then they are dangerous all year round. We put our peanuts into wire mesh feeders. That means the birds can only get a small piece at a time but we do it because it means the birds stay on the feeder longer where the sight of them can be enjoyed rather than dashing in, grabbing a whole nut and taking it away to chew pieces off. But, I don’t get paranoid if I happen to drop a couple on the ground.

Just how stupid do people think birds are? I’ve never heard anyone suggest that the local butcher’s shop should be closed because someone in the area has given birth and she might try and feed steak to her infant. Birds know perfectly well what food to give their young and, most sources say, it isn’t anything they get from feeders. Young birds get fed on insects, primarily, so the adults feed on the feeders to have the energy to search out enough insects for their young.

I don’t know of any scientific studies that show that adult birds will try and give inappropriate food to their offspring but this idea of not feeding peanuts or only giving them in mesh feeders or already crushed persists. It’s something ‘everybody knows’.

But why, you are entitled to ask, am I writing about feeding birds on a blog about plants poisons. Well, one of the other things that ‘everybody knows’ is that caffeine is a diuretic and you shouldn’t drink tea or coffee if you are thirsty. Caffeine occurs, naturally, in coffee beans from plants in the Coffea genus and in tea obtained from Camellia sinensis. It is often said that tea contains more caffeine than coffee which is half true. Pound for pound tea has more caffeine than coffee beans but a typical cup of each beverage will show more caffeine in the coffee than in the tea. It’s a bit like saying that cannabis is stronger these days because Cannabis sativa is grown to produce higher concentrations of the psychoactive components without taking account of the fact that non-problem users will moderate their intake to allow for this.

So, we have two questions. Is a cup of tea or coffee diuretic? Is caffeine diuretic? The idea that a cup of coffee is a diuretic has been around for over 75 years and is said to have been scientifically proven. The study that produced this conclusion took place in 1928. It involved only three subjects and lasted only a few hours. The subjects were given coffee to drink but there was no control group given water. So, when the subjects wanted to pee after drinking coffee there was no proof that someone drinking the same quantity of water would not have responded in the same way.

Since 1928, there have been a number of studies, still mostly involving just a small number of subjects. Of 23 such studies, 17 found no effect at all and the other 6 found incomplete indication of an effect. So, drinking tea or coffee gives you fluid in exactly the same way that drinking just water would.

The second of my two questions does seem to be true. There are studies that have found caffeine to be diuretic but only at doses way about what a normal tea or coffee drinker would have in a day.

When people on the Internet are not talking about feeding peanuts to birds they are talking about drinking 2l of water a day. Many of them will say that it has to be water because other drinks are diuretic. There is a mass of scientific evidence that, on balance, you are more likely to do yourself harm than good if you force-feed yourself with water just to reach your daily ‘quota’.

There are some bizarre arguments put forward. I’ve read a claim that, because two thirds of the coffee you drink becomes urine, drinking coffee increases dehydration. That would mean that coffee was made with some sort of magical negative water. Incidentally, it is not even true that two-thirds of what you drink is peed, irrespective of anything else. The body has a very sophisticated automatic system for regulating fluid content and how much you urinate will depend on your body’s fluid needs at the time.

But, all the evidence in the world counts for nothing when people, especially young people, are far more likely to respond to ‘my mate says’ than ‘the scientific evidence says’. So, it’s not about tea and coffee versus water and it’s not about feeding peanuts to birds. It’s about the huge effort put into ‘drug education’ without taking account of the fact that ‘my mate says’ will trump any amount of formal information campaigns, unless, those campaigns actually accept that what ‘my mate says’ about a substance may be quite close to the truth.  


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