Most of us like to think that our assessment of the world and the decisions we make are based on evidence, rationality and logic. However, we are emotional beings, full of prejudice and ego, with the added complication of media manipulation thrown in. Evidence-based decision making seems laudable, yet removing subjectivity from the evidence selection process itself is near impossible. Science makes valiant efforts to exclude emotional bias and self-interest through systematic testing and peer review before its conclusions are presented to the wider world as proof. It's the best show in town, but is far from perfect as scientists are emotional beings too, and often see their work 'sexed up' and selectively published (or not published at all) to meet commercial and political interests.
In 2009 the UK Food Standards Agency published a report, based on a study of 46 papers on the subject, suggesting there were no significant health benefits to be had from eating organic food. Their director, Professor Krebs, concluded that eating organic food was a "lifestyle choice", ie. that I as an organic farmer am a quack, and my customers are mugs. His words were leapt upon by the media, and undoubtedly contributed to a four year 25% decline in the UK organic market.
I was a little sceptical at the time; my instinct and common sense, based on 26 years of growing and eating organic food, is that the farming methods used in its production make a huge difference to how organic fruit and vegetables look, feel and taste. I find it unbelievable that these observable differences would not be reflected in the nutritional content too. Broadly speaking, the slow, steady soil-based growth typical of organic crops produces enhanced flavour, texture and, I would bet my house, more nutrition. So strong is my conviction (from common sense or prejudice perhaps?) that I would say if science fails to reveal this, it is the science that is at fault and not my vegetables.
Today, five years on, a new and much larger peer reviewed meta-study has been published in the highly respected British Journal of Nutrition. An international panel have looked at the data from 343 peer-reviewed, published studies in every possible way, and concluded that there are very significant nutritional benefits to be had from eating organic food. They found 18 to 69% more anti-oxidants (linked to reduced risk of many chronic diseases including neurodegenerative and cardiovascular diseases and cancers), far lower levels of pesticides (no surprise) and lower levels of toxic heavy metals like cadmium. I am even tempted to extrapolate to the conclusion that per unit of nutritional value, organic veg might even be cheaper.
Read more about the research at http://www.riverford.co.uk/why-organic-food.
How to explain the difference between the two studies? Perhaps science is not quite as objective as we are led to believe. The organic fraternity has alienated large parts of the scientific community through their resistance to GM and I can't help suspecting that, consciously or not, this might have influenced the weight given to individual studies in the analysis. Scientists tend to have a narrow focus in their view of the world; it is what makes them good at what they do. However I also suspect it makes them blinkered when considering their own fallibility in two areas; namely that they are subject to emotional bias like everyone else, and they perhaps have a tendency to undervalue what they don't know.
In the long run, science will reach a consensus on the nutritional benefit of organic food, as it has on smoking and cancer, and almost on anthropogenic climate change. That consensus will almost certainly be right, but for now common sense holds the casting vote for me and that means not spraying our vegetables with nerve toxins, accepting that they grow more slowly and that we occasionally must share them with a few bugs. They will often cost a little more as a result but that doesn't make my customers mugs or me a quack, just people who like good food and are making logical decisions.