May 26 2010
In 1952 Martin Gardner, who just passed away this week at the age of 95, wrote about organic farming in his book Fads and Fallacies in the Name of Science. He characterized it as a food fad without scientific justification. Now, 58 years later, the science has not changed much at all.
A recent review of the literature of the last 50 years shows that there is no evidence for health benefits from eating an organic diet. The only exception to this was evidence for a lower risk of eczema in children eating organic dairy products. But with so many potential correlations to look for, this can just be noise in the data.
Another important conclusion of this systematic review is the paucity of good research into organic food – they identified only 12 relevant trials. So while there is a lack of evidence for health benefits from eating an organic diet, we do not have enough high-quality studies to say this question has been definitively answered. It is surprising, given the fact that organic food was controversial in the 1950s, that so little good research has been done over the last half-century.
It should be noted that we only recently had any rules in the US regarding the label “organic”. According to the USDA:
The Organic Foods Production Act (OFPA), enacted under Title 21 of the 1990 Farm Bill, served to establish uniform national standards for the production and handling of foods labeled as “organic.”
The definition of organic entirely relates to the method of production, not the final product. It involves three principles. One is sustainable farming that is optimal for the environment. That question is beyond the scope of this medical blog. Many people do advocate organic farming for this reason alone, and many of the principles of sustainable farming are being incorporated more generally into agriculture and animal husbandry.
The second principle is the establishment of an ecosystem, using cover crops, crop rotation, and other methods. Again – I want to set aside the environmental questions and focus on the nutritional claims: Does organic farming result in produce that is more nutritious? There are different ways we can approach this question. One is addressed by the systematic review above: Can we measure a health advantage to eating an organic diet? The answer to that question at the present time is “no.” This could be due to the fact that there is no health benefit, or that any benefit is smaller than the studies currently available could detect. Long term modest health benefits are very difficult to detect with clinical trials, and it is therefore difficult to rule out such benefits, but at present there is no evidence of health benefits from an organic diet.
The second way to approach this question is to evaluate the food products themselves: Are they more nutritious? The most recent systematic review of the evidence concluded:
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.
There is also a recent study concluding that birds prefer seed that is conventionally produced over seed that is organically produced – likely because conventional production methods result in a 10% higher protein content.
The third issue with organic food is what is not in, or on them – pesticides, hormones and antibiotics. Here, again, we can take the same two approaches as with nutrition: Is there any evidence of a difference between organic and conventional produce, and is there evidence for a health benefit? There seems to be a consensus on the first question. There are lower levels of synthetic pesticides in organic produce and lower levels of hormones and antibiotics in organic meat than in conventionally grown equivalents. But is this safer for health? The review cited above is also relevant to this question, and essentially there is no evidence for greater safety of organic food over conventional food.
With regard to pesticides, it must also be noted that organic farming, while using methods to minimize pests and the need for pesticides, still uses organic, rather than synthetic, pesticides. For example a rotenone-pyrethrin mixture is commonly used. Such pesticides are not as well studied as synthetic pesticides, often require more applications, and may persist longer in the soil. In fact the use of “natural” pesticides is nothing more than an appeal to the naturalistic fallacy – there really is no evidence for superior safety, and they have not been adequately studied.
There is a recent study which has garnered a great deal of press linking organophosphates – a type of synthetic pesticide – to higher prevalence of ADHD. However, this is a preliminary observational study. While interesting, it really can only be used to justify further research, not any conclusions regarding the effects of organophosphates. (I discuss this article in more detail here.)
It does seem reasonable to minimize human exposure to pesticides. This can be accomplished, at least in part, however, by simply washing all produce thoroughly. I could not find any direct comparisons of organic produce to thoroughly washed conventional produce, but what evidence we do have suggests that residue levels are below safety limits and can be lowered further by washing. This is an area that does require continued monitoring and research, however.
Overall there does not appear to be any advantage for health to organic farming (sustainability and environmental effects being a separate issue). However, despite the fact that organic farming has been around for over 50 years, there is a surprisingly small amount of quality research available. The organic farming industry and popularity of organic products is growing. Organic products are more expensive, and questions remain about whether or not such methods would be adequate to supply our food needs. There may also be hidden health risks or unintended consequences to relying upon organic farming. There may also be benefits that have not been adequately documented. Therefore, this is one area where I think it is reasonable to conclude more research is genuinely needed.
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