A study just published in the Annals of Internal Medicine indicates that, by and large, organic food is neither more nutritious nor any less prone to bacterial contamination than corresponding, conventionally grown foods. Perhaps more importantly, the new study--a systematic review of prior research that pooled the findings from over 200 papers--found no evidence of a health benefit attached to organic foods.
But that doesn't mean organic food isn't better. You only get answers to questions you ask, and even then, only if the information is available. Absence of evidence is not the same as evidence of absence! We'll return to that notion before we're done.
To some extent, this is an important reality check. There has long been the tendency to conflate "organic" with "nutritious," both by individuals who are passionate advocates for organic farming and eating, and by those corporate entities that profit from the halo effect this confers. The motives of the individuals are pure and laudable, if at times overly enthusiastic. I am not so sure about the motives of all of the corporate entities, which shall remain nameless.
Organic does not mean "nutritious," and never did. Spinach may be grown conventionally, rather than organically, but will still have the nutritional profile of spinach, which is, of course, outstanding. Gummy bears--and sugar, for that matter--may be organic, and add nothing but empty calories to your diet.
The new study in the Annals reported that consumption of organic fruits and vegetables did reduce exposure to pesticide residues by roughly 30 percent overall. For whatever it's worth, pesticide levels were generally within the allowable limits for safety for the conventionally grown foods.
In the case of pure foods--such as produce--the meaning of organic is clear (grown without chemical fertilizers, herbicides, or pesticides) even if the health benefits are debatable. But when foods are assembled in recipes and packaged, then even the definitions can get murky.
According to the U.S. Department of Agriculture, any food wearing "organic" on its label must be "produced by farmers who emphasize the use of renewable resources and the conservation of soil and water to enhance environmental quality for future generations." Organic meat, poultry, eggs, and dairy products "come from animals that are given no antibiotics or growth hormones. Organic food is produced without using most conventional pesticides, fertilizers made with synthetic ingredients or sewage sludge [a comfort, to be sure], bioengineering, or ionizing radiation."
There is, of course, fine print with which to contend. A label that says "organic" is noteworthy for not saying "100 percent organic." Ninety-five percent of the ingredients in such a product must be organic, but the rest can be ... otherwise. In products "made with organic ingredients" up to 30 percent of the content need not be. We may get the truth on a food label, but rarely the whole truth.
The industry has done much to propagate the view that organic and nutritious are synonymous. Standard offerings in retail stores specializing in "natural and organic" may include, for instance, whipped cream and pepperoni pizza. In any other supermarket, shoppers would recognize these as dubious choices for health promotion--but under the halo effect of "natural and organic," shoppers may feel they can't go wrong nutritionally. I beg to differ.
Some studies have suggested that organic produce is, in general, more concentrated in nutrients than conventionally grown produce. The new study did not find evidence to support that as a general conclusion, but did find examples of it. There was some evidence of higher antioxidant levels in organic produce, and higher omega-3 levels in organic poultry and dairy. But no clear health benefits were discernible in connection to these. That lack of recognizable health benefit has been noted before. A prior systematic review in the American Journal of Clinical Nutrition, published in May of 2010, reported the same.
But as noted above, failure to find a health benefit may be more about absence of such evidence, than true evidence for the absence of such an influence. Let's consider what it would take to prove that organic foods confer a health benefit.
Imagine a clinical trial in which 1,000 people are assigned to strictly organic foods, and another 1,000 to conventionally grown foods, for 10 years--the two groups being just alike in all other ways. Such a trial would be enormously costly, cumbersome, and logistically demanding--if feasible at all. Some chemical contaminants would almost certainly get into the diets of the "organic" group despite the very best preventive efforts, and these would also contaminate the study, because they would narrow the intended difference between treatment groups.
Nonetheless, imagine there were three fewer cases of cancer, and/or of attention deficit hyperactivity disorder (ADHD), and/or perhaps several other maladies, in the organic group. Just "three fewer cases" over 10 years would be too few to distinguish from a statistical fluke in a sample of a thousand people. And, realistically, there might be even less than three fewer cases of cancer, because many cancers develop over a period of more than 10 years; a 10-year study might just not be long enough.
But let's imagine there were, indeed, three fewer cases of cancer, three fewer cases of ADHD, three fewer neurological ailments, and so on, in the organic group over a 10-year period. While none of this would be statistically distinguishable from random variation, it could matter a lot to public health. Three extra cases of cancer per 10 years in 1,000 people caused by pesticide residues would mean 3,000 extra cancers every 10 years per million people! In a population of 300 million, it means 300,000 extra cancers every decade!
So, a considerable health benefit of eating organic remains possible--but consigned to the world of statistical invisibility. These are very hard dots to connect, and we may need to make do with a relative "absence of evidence" for the foreseeable future.
Not a complete absence of evidence, however. A 2010 paper in Pediatrics, for instance, found higher levels of pesticide metabolites in the urine of children with ADHD. Pesticide residues may or may not "cause" ADHD, but they are at least implicated by association.
There are reasons not directly related to personal health why organic food may be "better" overall. In general, its production is kinder and gentler to the planet, and our fellow species. I am a strong proponent of organic food more on this basis than because of any clearly established health effects. If forced to choose between "nutritious" or "organic" for personal health, I would choose nutritious.
But we are not obligated to make that choice. Some of my favorite branded foods--such as Nature's Path cereals--get everything right, combining the benefits of organic with the benefits of great nutrition. When you have that option, I certainly endorse it. We also know that differences in contaminant levels between organic and conventional foods are much greater in some categories than others. The best guide I've seen on this topic was published by Consumer Reports in February 2006, and is entitled "When it Pays to Buy Organic." It matters far more for some fruits and vegetables than others, and matters as well for meat, poultry, and dairy--but not fish or seafood.
While we don't have, and are unlikely to get, definitive proof of personal health benefits of eating organic, it might be more reasonable for the burden of proof to go the other way: Since organic food is better for the planet and is likely to be better for health, we should accept it as such ... unless someone can prove it isn't. In the interim, recall that organic and nutritious do not mean the same thing, and beware marketing messages to the contrary.
Nutritious food is better for our health. Organic food may be as well, and it's better for the planet. So what may be best of all, systematic reviews notwithstanding, is to combine the two, whenever possible.
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David L. Katz, MD, MPH, FACPM, FACP, is a specialist in internal medicine and preventive medicine, with particular expertise in nutrition, weight management, and chronic-disease prevention. He is the founding director of Yale University's Prevention Research Center, and principal inventor of the NuVal nutrition guidance system. Katz was named editor-in-chief of Childhood Obesity in 2011, and is president-elect of the American College of Lifestyle Medicine.