Commentary on: British Study on Organic Foods

Very recently, The American Journal of Clinical Nutrition (AJCN) published a study conducted by the Department of Epidemiology and Population Health, London School of Hygiene & Tropical Medicine, UK.  The study was supported by the UK Food Standards Agency, and was entitled, Nutritional quality of organic foods: a systematic review.

The above study was founded on the premise that in spite of the growing consumer demand for organic foods, accurate information regarding the nutritional quality of organic foods is lacking.  The study sought to quantitatively assess the differences in reported nutrient content between organically and conventionally produced foodstuffs.  To accomplish this task, study researchers identified 162 studies (137 crops and 25 livestock products) and deemed 55 of these studies to be of satisfactory quality for actual analysis.  Here are the main results of the study:

1.  Conventionally produced crops had a significantly higher content of nitrogen, and organically produced crops had a significantly higher content of phosphorus and higher titratable acidity, and no evidence of a difference was detected for the remaining 8 of 11 crop nutrient categories analyzed.

2.  Analysis of the more limited database on livestock products found no evidence of a difference in nutrient content between organically and conventionally produced livestock products.

In light of the above results, the conclusion of the study reads as follows:  On the basis of a systematic review of studies of satisfactory quality, there is no evidence of a difference in nutrient quality between organically and conventionally produced foodstuffs.  The small differences in nutrient content detected are biologically plausible and mostly relate to differences in production methods.

The point of this post?  As an epidemiologist and a researcher myself, I am greatly intrigued by the results of this study, and feel that it is necessary to comment on it constructively.  Researchers in this study sought to compare the nutrient content between conventionally and organically grown foods, and essentially concluded that there was no evidence of meaningful nutrient differences between the two; Further, if small differences did exist, they would be because of differences in production methods. 

The point I would like to make here is this:  Production methods are precisely the point of departure, and the key difference between conventionally and organically grown foods, and they do matter.  While I applaud the researchers for doing a nutrient quality comparison between conventionally and organically grown foods, it is important to point out that there are several other endpoints that are relevant to health – which were not part of this study.  And, they do indeed relate to production methods.  Here are just a few of the many questions that still remain unanswered:

1.  Did conventional foods and livestock products have higher amounts of antibiotic, hormone, or pesticide residues?

2.  Did foods produced by conventional methods involve the use of Genetically Modified Organisms (GMO’s)?

3.  Was there a perceptible difference in taste quality between conventionally and organically grown foods? 

While the nutrient quality of foods is of great importance, I believe that there are numerous other “confounding” variables that are perhaps equally, if not more relevant, to our long-term health.  The reality is that the cumulative effects of the regular consumption of foods that may have measurable amounts of antibiotics, hormones, or pesticide residues are largely unknown, and there is sufficient epidemiologic evidence to reasonably conclude that the effects of these agents may be deleterious to our long-term health.  Further, many conventional methods of food production utilize GMO’s – the long term effects of which are also unknown.  Thus, prudence demands that we consider the comparison of these critically important factors as well in future studies.  

One of the key principles in the study of Epidemiology is always to remain acutely aware of what we have “left out” in a study.  The study under discussion successfully met its stated objective of nutrient comparison between organic and conventional foods.  However, if we are to use this study’s conclusion as a guideline to long-term health, we must keep in mind the variables that were either: 1) clearly outside of the purview of this particular study, and/or 2) still remain to be examined in future studies.

I wouldn’t consider an occasional (or regular) splurge on organic tomatoes or peaches a waste yet!  Notwithstanding some of the important reasons outlined above, the generally accepted superior freshness, taste, and flavor of locally and often sustainably produced organic foods are sufficient reasons for us to enjoy them still.

Resources: 

AJCN Study Abstract