By Professor Nigel Brown FRSB, President of the Microbiology Society.
There is a considerable amount of concern about the use of pesticides and herbicides in the environment, and specifically their use on the food we eat. There is no doubt that we need to prevent insects and microbes from damaging our food crops and different forms of agriculture have different ways of dealing with these. Organic food producers have made a number of claims about its benefits and, in spite of it generally being more expensive, organic food consumption increased by 4% in 2014.
Do the arguments about the health benefits of organic food stand up to scientific scrutiny? In spite of studies in 2009 and 2012 showing little or no benefit, a 2014 study from Newcastle University claimed that organic food is more nutritious and therefore healthier. However, this study has been dismissed as flawed. To quote one scientist ‘there are nutritional differences between two peas in the same pod’ so such studies have to be done very carefully. The majority scientific opinion is that organic foods have no added nutritional benefit over other foods.
Do they have benefits in limiting exposure to pesticides and fertilisers? Certainly, the Soil Association, the body which accredits organic food production, limits the number and identity of pesticides and fertilisers that can be used in organic farming. However, the pesticide Bordeaux mixture, composed of copper sulphate and slaked lime, can cause copper toxicity to soil if used too frequently. Another permitted pesticide is the harmless bacterium Bacillus thuringiensis, which is a close relative of the anthrax bacillus – organic farmers rarely advertise that fact! The fatal outbreak of E. coli infection in Germany in 2011 may have arisen from the use of manure in place of chemical fertilisers on organic bean sprouts.
So, is organic farming good for the environment? While there is a reduction in greenhouse gas production (GHG) per hectare due to the ban on chemical fertilisers, more land is required and often more machinery is used, so GHG production is similar to intensive agriculture. As yields of major cereals are low compared with intensive farming, it is estimated that 25% more land is required for organic farming compared with conventional agriculture. Some studies suggest that organic farming increases biodiversity, but this appears to be small compared with the effects of other factors, such as how soil is tilled and weather effects. However, organic farming uses less water and causes lower pollution of rivers than intensive farming.
So should you eat organic foods? The decision is entirely personal, but some of the justifications of health and environmental benefits do not stand up to detailed scrutiny. Costs, food miles and eating preferences are more important in that decision. Many people who eat organic foods are healthier eaters anyway – they eat more fruit and vegetables. Whether or not the food is organic is probably irrelevant.
Professor Brown FRSB is writing an article each month for The Bridge, a local magazine delivered to every home in the villages of Corsley and Chapmanslade in Wiltshire.
The Royal Society of Biology is sponsoring these articles through our regional grant scheme, which supports locally focussed activity.