This piece has also been published by the Genetic Literacy Project and the Fitness Reloaded blog.
I spent over a decade of buying little else than organic food. During that whole time, I never justified my choice by claiming that non-organic vegetables were less nutritious or somehow less healthful. (I just thought that the environment was better off with organic farming. That is another story: Natural assumptions and On farming, animals, and the environment.)
It was first a couple of years ago that I became aware of people claiming that organic produce would somehow possess a superior wholesomeness. I was confused, and when I learned of an extensive meta-analysis (‘The Stanford Study’) which had concluded there was no nutritional difference between conventionally and organically farmed food, I wasn’t fazed. Why would there be a difference?
For a discussion on that The Stanford Study, you can see this article News in Standford medicine – Little evidence of health benefits from organic foods:
“The most comprehensive meta-analysis to date of existing studies comparing organic and conventional foods.”
or you can also find here a direct link to the paper – behind paywall.
Still I kept running into arguments insisting that the jury was still out there, or that, indeed, that organic food was most certainly superior. If any evidence is provided, it may often be in the form of an anecdote – that people can taste the difference. This is a poor way to truly determine nutrition or truly, even taste perception, as being told the food is organic makes people rate it higher.
I have heard people argue that organic food would be more nutritious than conventionally grown food. Usually, as evidence of this view, they have presented this meta-study, titled: “Higher antioxidant and lower cadmium concentrations and lower incidence of pesticide residues in organically grown crops: a systematic literature review and meta-analyses.” I will call it the High Antioxidant study. I’ve written about this topic earlier as a case study of bias – Am I biased? Are you? – but to cut to the chase, I will include only the summarised review of the science here.
Shortly, should we start buying organic food to reap health benefits? No. Several comprehensive reviews support the view that there are no nutritional or health benefits from organic products. I will lay them out for you below.
To know more about the robustness of the conclusion reached in the High Antioxidant study, I searched for critical evaluations on it. The next logical step after that was to compare it to other similarly extensive sources – other reviews and meta-analyses.
First I found a source, Science 2.0, criticising the High Antioxidant study for being too inclusive, for not dismissing studies with flawed methodology. From Science 2.0:
They used a lot of papers, that is a good thing if there is actually a large body of knowledge and it is rigorous, but in even the most controversial toxicological issue, the EPA will end up disqualifying all but about a dozen papers due to lack of underlying data being included or methodological concern. In a review, they look at no data, of course, and 343 papers becomes the problem rather than the solution when the methodology is flawed.
Meta-analysis, as everyone with statistics knowledge knows, can boost the strength of systematic reviews when done properly but easily suffers from bias unless the researchers are truly interested in controlling eligibility criteria and methodological quality. Without controlled eligibility, it’s easy to find any pattern you want. With Web of Knowledge search terms like ‘organic’ and ‘biodynamic’, it’s really easy to skew the inclusion. Then they synthesized their dramatically different studies using a random effects model.
There was also criticism of the study’s claims that antioxidants reduce risk of chronic illness, both by Science Media Centre, Nutritional content of organic and conventional foods, and pharmacologist Ian Musgrave over at The Conversation, Organic food is still not more nutritious than conventional food:
While consumption of antioxidant containing fruit and vegetables have been associated with better health outcomes, the antioxidants themselves do not appear to have any role in this effect (see also here, here and here), despite the number of television advertisements that exhort us to buy antioxidant enriched food. Indeed, the major finding is that high concentrations of fat soluble antioxidant vitamins are associated with detrimental effects.
Ian Musgrave points out the lack of significance in the difference of vitamin and antioxidant levels – carotenoid in fruits was 50% higher, for instance, but then, fruits are a poor source of carotenoid all in all, and our intake mainly comes from vegetables, which have much more carotenoids, and the vegetables showed no difference between organic and conventional. Organic apples had 6% more vitamin C. For recommended daily intake you’d need 5.3 organic vs 5.6 conventional apples. Pesticide and cadmium levels were likewise low for both, with no demonstrable harm from residue of either (the food we have in the western world is the safest humans have ever eaten, and pesticides are one of the least of our worries, see more here and here).
Ian Musgrave continues with the context of natural variability:
the nutritional value of foods is very variable, influenced strongly by local regional factors, variations in growing seasons and rainfall, ripeness of food when harvested and time of harvest. I’m writing this is South Australia, possibly the wine capital of Australia, where we know that having vines on the different sides of a hill will affect sugar and flavor of the grapes. Even different cultivars of the same crop may vary significantly in composition due to the factors above. Nutritional values of crops can vary from between 100% to nearly 200% (which should be kept in mind when the differences reported between conventional crops and organic crops run from 6-69%).
So perhaps the High Antioxidant study didn’t reach such a strong conclusion for benefits of organic produce after all. I had earlier read a report of a study that came to a different conclusion. Being a non-expert with limited time and resources, I was not actually sitting down to read through to understand in detail the studies’ merits myself. My bias might let me take the word of one, and falsely ignore the points of the other. How could I avoid that? My best approach would be to see what wisdom yet other reviews would bring to the table.
The Conversation mentioned two other reviews concluding no difference. I found that a medical science blogger, Steven Novella MD, had made a summary of the existing meta-analyses on the topic. He had looked at the High Antioxidant study and laid it out with four other reviews on the topic. He begins with a great principle of how to approach a scientific question.
Whenever I am trying to quickly grasp the bottom line of any scientific question, I look for a consensus among several independent systematic reviews. If multiple reviewers are looking at the same body of research and coming to the same conclusion, that conclusion is likely reliable.
In this case, there are three [he later added a fourth, see below] other recent large systematic reviews and meta-analyses of the same research on the nutritional content and safety of organic vs conventional produce. The other three studies all came to the opposite conclusion as the current [High Antioxidant] study.
Here are the studies, a 2009 review by Dangour et. al. 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.
A 2010 review also by Dangour found:
From a systematic review of the currently available published literature, evidence is lacking for nutrition-related health effects that result from the consumption of organically produced foodstuffs.
And a 2012 review by Smith-Spangler et. al., which I had read about earlier (the ‘Stanford study’) found:
After analyzing the data, the researchers found little significant difference in health benefits between organic and conventional foods. No consistent differences were seen in the vitamin content of organic products, and only one nutrient — phosphorus — was significantly higher in organic versus conventionally grown produce (and the researchers note that because few people have phosphorous deficiency, this has little clinical significance).
Novella adds another 2002 review which also finds no nutritional difference.
At this point I am satisfied with my conclusion. It must be reasonable to assume, that should there be a stable measurable difference in the nutritional content of organic food, other reviews would be able to arrive at that conclusion independently of each other. Instead, we have four reviews on similar lines – finding no nutritional or health benefits of organic food. Then we have one study stating a different conclusion, but at a closer look demonstrating very little differences for a few nutrients, likely at a level of no consequence for our health or nutrient intake.
Could the four of them be deeply flawed and the High Antioxidant one be the best of the bunch? Could future studies show a much greater difference in nutrient content? That is possible, but based on the evidence at the time, it does not seem likely.
I am reorganizing a few of my posts (changing them from pages to posts for logistic reasons), but I didn’t want to lose the comment left before by Morelambchops. Here it is, as well as my reply:
March 27, 2015 at 3:25 pm
Not only does organic still use pesticides, it also uses more of them. It uses more cultivation and wasted fuel emissions. More manure which leads to e. Coli and easier contamination, illnesses. A much higher carbon footprint. Tearing up the soil through organic cultivation harms the environment by washing away the soil and polluting waterways. It requires more land for less food. If everyone wanted organic we would need an extra 140+ million acres of land….so which forest shall we cut down first? We are a non-organic farm family who’s been in this business 159 years. 100% of farmers I’ve met who switched to organic did so because they knew they could sell a nutritionally equivalent product for 3x the money…. But were surprised by the higher carbon footprint. It’s sad when people buy in to the marketing scam “organic” which is counterproductive to their environmentally-“friendly” agenda.
Liked by you
March 27, 2015 at 3:34 pm
I used to be big on organic, but have been learning more abut agriculture the past couple of years and, sadly, it all reflects just what you say. You might be interested in these posts, which look at the science of environmental effects of different farming methods:
On farming, animals, and the environment https://thoughtscapism.com/2015/02/24/on-farming-animals-and-the-environment/
GMOs and the environment https://thoughtscapism.com/2015/03/22/gmos-and-the-environment/
Reblogged this on TSFWON: the small fuzzy world of nothing and commented:
Our friends over at thoughtscapism have a wonderful blog entry worth a look if you missed out. I spent a lot of time buying only organic foods before beginning to look critically at the science behind the dollars I was spending. It’s interesting to read about other people going through the same thought processes…
This meta study “Higher antioxidant and lower cadmium concentrations and lower incidence of pesticide residues in organically grown crops: a systematic literature review and meta-analyses.” show somethings a bit different http://www.ncbi.nlm.nih.gov/pubmed/24968103
“The concentrations of a range of antioxidants such as polyphenolics were found to be substantially higher in organic crops/crop-based foods, with those of phenolic acids, flavanones, stilbenes, flavones, flavonols and anthocyanins being an estimated 19 (95 % CI 5, 33) %, 69 (95 % CI 13, 125) %, 28 (95 % CI 12, 44) %, 26 (95 % CI 3, 48) %, 50 (95 % CI 28, 72) % and 51 (95 % CI 17, 86) % higher, respectively. Many of these compounds have previously been linked to a reduced risk of chronic diseases, including CVD and neurodegenerative diseases and certain cancers, in dietary intervention and epidemiological studies. Additionally, the frequency of occurrence of pesticide residues was found to be four times higher in conventional crops, which also contained significantly higher concentrations of the toxic metal Cd. Significant differences were also detected for some other (e.g. minerals and vitamins) compounds. There is evidence that higher antioxidant concentrations and lower Cd concentrations are linked to specific agronomic practices (e.g. non-use of mineral N and P fertilisers, respectively) prescribed in organic farming systems. In conclusion, organic crops, on average, have higher concentrations of antioxidants, lower concentrations of Cd and a lower incidence of pesticide residues than the non-organic comparators across regions and production seasons.”
I actually use a large part of the piece above discussing this study. It is the only one to claim they find a difference, but the differences they find are so small as to be quite insignificant from a consumer health point of view (and natural variation from weather, location, etc are also great). Even a large percentage difference is not meaningful in vegetables/fruit that are very low on said antioxidant to begin with – also for many antioxidants, there is actually lack of evidence for health effects for consuming extra, and in some cases there are drawbacks . At the same time, no other review has come to the same conclusion of even a slight significant difference, making this one the odd one out. Many links to further discussions also included in the piece above. Hope you find the analyses informative.
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I really like your articles. They’re packed with information, but accessible and not condescending. With the meta studies available it really does look like organic farming doesn’t have much going for it.
Do you know much about organic livestock farming though? I’m assuming they’re working on the same terrible appeal to nature principles, but do they possibly at least treat the animals better? Since part of their appeal is naturalness which is associated with goodness, wouldn’t it be important for them to be seen as animal loving?
thanks a lot for letting me know! Much appreciated.
I touched on the questions of organic lifestock farming more in this piece:
The short answer is that it very much depends. Choosing an organic label across the board doesn’t guarantee better/more accommodating animal handling. In some cases they can provide more access to outdoors, or a percentage of feed that must be gras for cows, etc. It’s a bit of a troublesome case of the consumer needing to really dig to find the specs of what applies to where they are buying from.
Unfortunately the ‘naturalness’ of it often requires non-GMO feed and ‘natural’ medicine too – which has a potential to lead to prolonged suffering of sick animals.
There is a research paper calling out exactly what you mention – that this the animal handling aspect is what many organic customers want and for that, they should get some wider common requirements in place.
There are other labels that actually focus more on the animal welfare bit, and I use these nowadays in Switzerland, for instance.
Thanks for stopping by and dropping a line!