Tim's Blog

Following on from yesterdays news about the nutritional quality of organic food, I have now had time to read the article in the American Journal of Clinical Nutrition (July 2009) and quickly scanned the source report Comparison of putative health effects of organically and conventionally produced foodstuffs: a systematic review from the Nutrition and Public Health Intervention Research Unit, London School of Hygiene & Tropical Medicine.

It also emerges from email correspondence that the British Food Standards Agency is known for its pro-GM and anti-organic stance.

On reading the studies I was fascinated to note that only 3 studies, of 11 (a very small number given the very broad time frame- from 1958) were considered relevant and met the satisfactory quality criteria for consideration.

There is no way this can be claimed as a meta-analysis of the literature, therefore, as the sample is way too small, and it also puts in doubt whether this is intended to be a fair systematic review, as the exclusion criteria have been skewed for a particular bias.

The study is further flawed as conclusions are drawn from all eleven studies considered (not the 3 deemed of rigorous quality), even though 8/11 were considered sub-standard.

The final conclusion that because of the lack of sufficiently rigorous studies (not evidence, and the difference is very important) considered in this paper that there is no evidence of the benefit of organic food is extraordinary, and really smacks of a vested interest in the reporting of the results to undermine arguments for organic practices and systems.

On the contrary, the correct conclusion from these data is that it is not possible to comment at all, as the limitations of the study make it "so small as to be unanalysable".

The authors should be suggesting that further studies need to be conducted and that alternative ways of looking at both existing and potentially new data need to be considered if this question is to be answered through the science.

Choice of organic foods is usually based on much broader issues such as sustainability, which was not considered. Comparisons between organic and non-organic should consider both nutritional qualities and residues (anti-nutritional factors) in the same samples.

Given these problems, I am highly sceptical that all relevant studies have been included, and we can be pretty certain the methodological selection frame is seriously flawed.

Visit our Forum on "Nutrional Quality of Organic Food" to discuss this further with other members.