You've probably seen headlines the past few days saying, essentially, that organic food is worthless. The headline on a Reuters report is typical. It says that a study finds "Organic food not healthier." The headline suggests that a study found that there are no health benefits to growing and eating organic food on any level. It suggests we are wasting our money by paying more for it.
But did the study really reach that result? And if it did has it proved what the news stories suggest?
Here's a closer look at the details.
First, here is the sort of news story you will have seen.
Organic food not healthier, study finds
LONDON (Reuters) – Organic food has no nutritional or health benefits over conventionally produced food, according to a major study published on Wednesday.
. . .
Researchers from the London School of Hygiene & Tropical Medicine said consumers paid higher prices for organic food in part because of its perceived health benefits, creating a global organic market worth an estimated $48 billion in 2007.A systematic review of 162 scientific papers published in the scientific literature over the last 50 years, however, found there was no significant difference.
"A small number of differences in nutrient content were found to exist between organically and conventionally produced foodstuffs, but these are unlikely to be of any public health relevance," said Alan Dangour, one of the report's authors.
"Our review indicates that there is currently no evidence to support the selection of organically over conventionally produced foods on the basis of nutritional superiority."
. . .
So, to summarize, the news story makes a BIG claim about the global value of organic food - that this study proves that organic food is absolutely no better that conventionally grown food and thus a waste of dollars.
That story also included a criticism of the study’s methodology and conclusions. Here is what it says.
Peter Melchett, policy director of Britain's Soil Association, which promotes organic farming, said he was disappointed by the conclusions reached by the study's authors.
He criticized the methodology of the study, which he said had led researchers to reject some clear nutritional benefits as "not important."
Melchett also pointed out there was not sufficient research to assess the long-term effects of pesticides on human health.
The criticism is that the study was poorly done and the claims made not supported, because it looked only at a small picture - i.e. nutrients in food - and it failed to consider the impact of pesticide use on health. I would add that it also failed to consider the use of conventional fertilizers and other chemicals on food.
It should also be noted that the study is a meta-study. It examined the results of a large number of studies. Such a study can have powerful effects and be quite useful, but one has to be careful about how the data from diverse sources are treated.
Here is more detail about the study itself.
First, here is a bit about the London School of Hygiene & Tropical Medicine in its Mission Statement
To contribute to the improvement of health worldwide through the pursuit of excellence in research, postgraduate teaching and advanced training in national and international public health and tropical medicine, and through informing policy and practice in these areas.
I am puzzled about the tropical health focus and what that means about these researchers. The hygiene part also seems off the mark for the subject, but the first author, for example, has a track record of research into nutrition, if not organic versus conventional foods.
Given more time, it would be interesting to track down the records of each of the authors. But not today.
Here is the LSHT's summary of the study methodology and results. It states that this is solely a study of nutritional content and not of any other aspect of the food production methods under consideration.
Researchers from the London School of Hygiene & Tropical Medicine have now completed the most extensive systematic review of the available published literature on nutrient content of organic food ever conducted. The review focussed on nutritional content and did not include a review of the content of contaminants or chemical residues in foods from different agricultural production regimens.
. . .
Alan Dangour, of the London School of Hygiene & Tropical Medicine’s Nutrition and Public Health Intervention Research Unit, and one of the report’s authors, comments: ‘A small number of differences in nutrient content were found to exist between organically and conventionally produced foodstuffs, but these are unlikely to be of any public health relevance. Our review indicates that there is currently no evidence to support the selection of organically over conventionally produced foods on the basis of nutritional superiority. Research in this area would benefit from greater scientific rigour and a better understanding of the various factors that determine the nutrient content of foodstuffs’.
The statement is a fair statement of the study as set out in the study abstract:
Background: Despite growing consumer demand for organically produced foods, information based on a systematic review of their nutritional quality is lacking.
Objective: We sought to quantitatively assess the differences in reported nutrient content between organically and conventionally produced foodstuffs.
Design: We systematically searched PubMed, Web of Science, and CAB Abstracts for a period of 50 y from 1 January 1958 to 29 February 2008, contacted subject experts, and hand-searched bibliographies. We included peer-reviewed articles with English abstracts in the analysis if they reported nutrient content comparisons between organic and conventional foodstuffs. Two reviewers extracted study characteristics, quality, and data. The analyses were restricted to the most commonly reported nutrients.
Results: From a total of 52,471 articles, we identified 162 studies (137 crops and 25 livestock products); 55 were of satisfactory quality. In an analysis that included only satisfactory quality studies, 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. No evidence of a difference was detected for the remaining 8 of 11 crop nutrient categories analyzed. 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.
Conclusions: 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.
Here are my criticisms of the study and of the way the news has "reported" it.
It sounds impressive to do a meta-study of >50,000 articles. However, there are problems.
1. A study of research stretching over 50 years, i.e. 1958 - 2008 is problematic. There have been huge changes in agricultural practices during those periods and the content of chemicals used and organic practices developed. It seems likely that a conventional farmer in 1958 might have farmed more like an organic farmer today than a conventional farmer today. In fact, to arrive at the conclusion here, they might have been better off simply doing their own controlled study or studies.
2. They were looking for only a handful of nutrients, while food contains many more nutrients, and nitrogen and phosphorus may not be the most important of the nutrients. We have learned that phytochemicals in foods and many other elements play important roles.
3. They do not examine chemical residues from pesticides and fertilizers.
4. By treating all these studies as if they took place at one time and measured one constant, they ignore important variables. Time and different agricultural practices are two already mentioned. Soil quality and content is another. There are many other complex issues not included.
So, not to fault the researchers, it is WAAAAYYYY too big a stretch for the news stories to make the screaming headline claims they do.
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