'Natural' and 'good for you' don't always go together

By Associate Professor Allan Blackman

This article was orignally published in the Otago Daily Times on Monday 8 October 2001.

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To GE or not to GE? That is the question facing New Zealand at the moment. The Royal Commission on Genetic Modification released its findings in July and the Government is due to issue a report on these findings by the end of this month. One of the major concerns of those opposed to genetic modification is that field trials of genetically modified crops may lead to contamination of other species in the environment. Such contamination would threaten New Zealand’s budding organic farming industry, which is currently worth at least $60 million in export earnings.

In this month’s column, I’d like to talk about the concept of “organic” in Chemistry terms. To do this, I need to delve into a bit of Chemistry history. Chemistry as we know it today really started to evolve apace around the 16th century and the term “organic” was originally used at this time solely to describe compounds derived from living sources (e.g. plants and animals). All other compounds were termed, somewhat unimaginatively, “inorganic”. Organic compounds were believed to be imbued with a “vital force” and it was thus thought to be impossible to prepare organic compounds in a laboratory starting from inorganic materials. However, in 1828, Friedrich Wöhler accidentally managed to do just this by synthesising urea, a constituent of urine, from the inorganic compound ammonium cyanate. Once the idea of a “vital force” had been disproved, the term “organic” evolved to refer to compounds composed primarily of carbon and hydrogen, and indeed, this is the currently accepted definition of organic as it applies to Chemistry today. In fact, most compounds derived from living sources are composed primarily of carbon and hydrogen, and so our current definition of organic encompasses the original.

However, I imagine most of you reading this are more familiar with the term “organic” in the context of organic agriculture and horticulture. In this case, organic refers to produce that is grown without the use of fungicides, herbicides, insecticides, growth regulators and other agricultural chemicals, relying instead on “natural” fertilisers such as lime, dolomite and ground phosphate (ironically all three are classified by chemists as inorganic materials) or fertilisers based on fish and seaweed. One of the aims of organic farming is to reduce the amount of “artificial” chemicals in the environment and this is indeed a laudable goal. We have been and are currently guilty of polluting the environment with any number of harmful compounds, both organic and inorganic. But it is also important to recognise that just because something is “natural” doesn’t mean to say that it’s necessarily good for you. In fact, some of the most potent poisons known to mankind are derived from nature. Socrates was put to death by being forced to drink a hemlock extract, and even the leaves of the humble rhubarb plant are poisonous. One of the most toxic substances on planet earth is palytoxin. This is a naturally-occurring organic (in the sense of being composed primarily of carbon and hydrogen) compound obtained from coral, and its toxicity is quite extraordinary – it has been estimated that as little as four micrograms may be enough to kill a human. To give you some idea of what a truly tiny amount this is, a grain of salt weighs about one hundred micrograms. Or to put it another way, one teaspoonful of palytoxin would be enough to wipe out the population of Auckland. Thankfully, the coral from which palytoxin is derived is found only in Hawaii, in a single tidal pool measuring 2 metres by 1 metre.

So when someone tells you that all natural compounds are good for you, take it with a grain of (all natural) salt.

October sees Chemists all over the world polishing up their acceptance speeches for the Nobel Prize in Chemistry. While I can’t say I’m expecting the award this year, in next month’s column, I’ll tell you who won and why.