I recently read a commentary by Dominic Lawson, in the Times of London Sunday edition, entitled “Organic Food is Just a Tax on the Gullible.He was referring to a couple of systematic reviews (health benefits and nutritional content) that suggest there are no measurable health benefits an no meaningful nutritional superiority associated with organically produced food . The studies and the commentary add some useful detail to my previous comments about nutrition myths, and they illustrate nicely the seldom-appreciated complexity of making sound decisions about producing food, whether for animals or humans.
Now I’ll admit to a certain sympathy with organic food production, particularly as it seems likely to be less harmful to the environment than conventional industrial agriculture. And I have no doubt that the economic incentives of the agriculture industry lead to just as much malfeasance as those in the pharmaceutical game, or really any other area of economic activity. I believe we now produce more food, of better quality, more efficiently in terms of calories per acre that ever before, and that is itself a good thing, at least for our health as individuals and as a species. However, this increased production comes at a cost, and the use of fossil fuels and pesticides has consequences we must be mindful of.
Nevertheless, I believe in applying the same standards of evidence to all scientific claims, including those I personally find appealing. And I have been skeptical in the past of the nutritional and health claims of organic food proponents, which seem to be based more of the naturalistic fallacy than on any evidence I’m aware of. A reader here suggested I had missed this evidence: “there are increasing numbers of studies documenting that (certified) organic food is more nutritious than conventional (non-certified organic food). They find significantly more minerals, vitamins, antioxidants in most all foods researcher look at.” Unfortunately, the person never responded to my subsequent request for details on these studies.
The first of the reviews Lawson comments on examined the literature from 1958-2008 and found only 11 studies that addressed the question of health benefits from organically produced foods or specific food ingredients. Of these, only 3 studies met the a priori defined criteria for methodological quality. The authors concluded, ” because of the limited and highly variable data available, and concerns over the reliability of some reported findings, there is currently no evidence of a health benefit from consuming organic compared to conventionally produced foodstuffs.” Clearly, this study does not definitively show that there are no health benefits to organically produced foods. But it does show that there is no high quality evidence for such benefits in the literature, which leaves the burden of proof squarely on those who make claims for the health benefits of eating organic foods.
The second study reviewed the literature for the same period, and did slightly better in terms of finding high quality studies. Of over 3000 studies examined, 55 met the quality standards. Based on these, the authors concluded:
“No evidence of a difference in content of nutrients and other substances between organically and conventionally produced crops and livestock products was detected for the majority of nutrients assessed in this review suggesting that organically and conventionally produced crops and livestock products are broadly comparable in their nutrient content. The differences detected in content of nutrients and other substances between organically and conventionally produced crops and livestock products are biologically plausible and most likely relate to differences in crop or animal management, and soil quality. It should be noted that these conclusions relate to the evidence base currently available, which contains limitations in the design and in the comparability of studies. There is no good evidence that increased dietary intake, of the nutrients identified in this review to be present in larger amounts in organically than in conventionally produced crops and livestock products, would be of benefit to individuals consuming a normal varied diet, and it is therefore unlikely that these differences in nutrient content are relevant to consumer health.”
These two reviews have been criticized, not surprisingly, by organic food producers, primarily for their exclusion of studies which support the producers’ claims. Ben Goldacre has already responded to the substance of these criticisms. Clearly, these two reviews cannot not be the final word on the subject. They strongly suggest that when the scientific literature does not support the claims that organically produced food is healthier or more nutritious than conventionally produced foods, but they also show that the evidence is sparse and of poor quality, so we must keep an open mind on the subject. And, of course, none of this bears on the other potential benefits of organic agriculture, including decreased environmental harm and subjective benefits such as better tasting food. These are themselves issues which ought to be investigated in a rigorous way.
Finally, Lawson’s commentary made what I thought was a critical point, nicely illustrate by an anecdote that is humorous, rather than tragic, only because it ended happily. I’ll let him tell it:
“A few years ago my wife decided we should have an entirely organic vegetable garden. To this end she refused all man-made fertilisers [sic] and ordered a truckload of pigeon droppings. What could be more natural? Neither was there anything unnatural in the germs I inhaled through the spores of our organic manure, thereby contracting psittacosis. This developed into “atypical” pneumonia, which was of course resistant to all standard antibiotics. Had a hospital doctor not guessed the cause and put me on a drip with the appropriate drugs – ooh, chemicals! – I could have become a fatal casualty of the organic movement. Obviously my wife might have ordered cow manure rather than pigeon poo[p]; then I could have been felled by E coli instead.”
This is a powerful illustration of a concept promoters of CAM often ignore; every choice has an array of costs and benefits that have to be evaluated and balanced. Vaccines do sometimes cause harm, but to a far lesser degree than the harm of not using them appropriately. And there may be benefits to reducing the use of chemical fertilizers, but one cannot just blithely follow the naturalistic fallacy and assume that organic fertilizers are always better. This sort of cost benefit analysis is always difficult, tedious, and fraught with uncertainty, and it lacks the appeal of simplicity, but it is a crucial part of making the best decisions about medicine, agriculture, or any other complex endeavor.