Organic Crops Do Not Really Offer More Health Benefits

The believers in the organic
religion had a
heyday earlier this week when a bunch of organic farming
researchers published an article in the British Journal of
Nutrition (BJN) that found, (gasp), that organic crops are

more nutritious than conventional crops. Specifically, the
researchers put together an meta-analysis of 343 studies that in
some way related to the nutritional aspects of organically and
conventionally produced crops. They found…

…organic crops, on average, have higher concentrations of
antioxidants, lower concentrations of Cd [cadmium] and a lower
incidence of pesticide residues than the non-organic comparators
across regions and production seasons.

Based on these results should you rush out to Whole Foods right
now? Probably not.

This meta-analysis was doubtlessly undertaken to counter two
earlier meta-analyses that found no signficant nutritional
differences between organic and conventional crops. The first was
published in 2009 in the American Journal of Clinical
Nutrition which
reported:

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 food-stuffs. The
small differences in nutrient content detected are biologically
plausible and mostly relate to differences in production
methods.

A larger study published in the Annals of Internal
Medicine in 2012 found:

The published literature lacks strong evidence that organic
foods are significantly more nutritious than conventional foods.
Consumption of organic foods may reduce exposure to pesticide
residues and antibiotic-resistant bacteria.

So did the new study find anything of consequence with regard to
how consuming organic foods affects human health? Not really.

It is possible (probable even) to quibble with how any
meta-analysis is put together. For example, the organic researchers
in the new BJN study assert:

The main reason for the inability of previous studies to detect
composition differences was probably the  highly limited
number of studies/data sets available or included in analyses by
these authors, which would have decreased the statistical power of
the meta-analyses.

Well, maybe. Alan Dangour, a researcher associated with the
earlier meta-analyses that found no signficant nutritional
differences returns the
favor of criticism:

The authors of this new systematic review that primarily aims to
identify differences in nutrient content between organically and
conventionally produced foods have brought together a large number
of studies published over a 20 year period.  The quality of
the available data varies greatly and it is therefore very
surprising that, in their analysis, the authors decided to include
all the data that they found, irrespective of their
quality.  In fact the study authors themselves note that
there are significant concerns with the consistency and reliability
of some of their findings.  Mixing good quality data with bad
quality data in this way is highly problematic and significantly
weakens confidence in the findings of the current analysis. 
It is a shame that greater care was not taken in trying to ensure
that the analyses were based only on reliable and scientifically
robust data from satisfactory quality studies.

So it goes.

Interestingly, many head-to-head comparisons in which organic
crops are grown next to conventional ones find no important
differences in nutrition. For example, a 2009 study comparing many
of the same anti-oxidant compounds in the BJN study between organic
and conventional wheat found “no statistically
significant differences between the two farming systems.” A
2011 study on tomatoes reported that “organically grown tomato is

no more nutritious than conventionally grown tomato when soil
fertility is well managed.” On the other hand, a same farm study in
2010 did find that “organic management and fertilization have a
positive
effect on the accumulation of certain beneficial minerals and
phenolic compounds in eggplant.”

Given these sorts of contradictory findings, it is possible to
cherry-pick your way to the results you want. Not that anybody
would ever do that.

But let’s assume the results are real. Do they have any
appreciable health consequences for people? Consider, for example,
a 2014 prospective study comparing women who regularly eat organic
foods with those who don’t that concluded:

In this large prospective study there was little or no decrease
in the incidence of cancer associated with consumption of organic
food, except possibly for non-Hodgkin lymphoma.

A 2011 study of the risks posed
by pesticide residues on conventional crops concluded
that…

…(1) exposures to the most commonly detected pesticides …
pose negligible risks to consumers, (2) substitution of organic
forms of the twelve commodities for conventional forms does not
result in any appreciable reduction of consumer risks….

What about the higher levels of toxic cadmium in conventional
crops? Those levels tend to depend on the soils in which crops are
grown, not the method of cultivation. The study does not appear to
have controlled for such variations. In any case, a 2007 Belgian
study found that organic crops can contain
higher levels of cadmium than conventional ones.

Finally, the findings on anti-oxidant levels were the chief
reason the study got the attention of the media. Do they matter
with regard to human health? Charles Benbrook, one of the
researchers in the BJN study
acknowledges:

Our team, and indeed all four reviews, acknowledges that many
questions remain about the bioavailability of plant-based
antioxidants, how necessary they are at different life stages, and
how inadequate intakes shift the burden of disease. But our view is
that the weight of evidence supports linkages between higher
antioxidant intakes and improved health outcomes, despite inability
to quantity such linkages or predict fully which factors drive
them.

Actually, the weight of the evidence strongly indicates that
eating
5 to 9 servings of fruits and vegetables every day – either
grown conventionally or organically – provides significant health
benefits, including those associated with the consumption of
plant-derived anti-oxidant compounds. Interestingly, the BJN study
found…

…significantly higher concentrations of total carbohydrates
and significantly lower concentrations of proteins, amino acids and
fibre in organic crops/crop-based compound foods.

Somewhat amusingly, the authors observe:

The nutritional significance/relevance of slightly lower protein
and amino acid concentrations in organic crops to human health is
likely to be low, as European and North American diets typically
provide sufficient or even excessive amounts of proteins and
essential amino acids.

Of course, exactly the same thing can be said with regard to
plant anti-oxidants among those Europeans and North Americans who
eat their recommended daily servings of fruits and vegetables
however grown.

Let’s conclude with some
sage advice from Richard Mithen, research leader of the Food
and Health Programme at the Institute of Food Research in Britain:

“The additional cost of organic vegetables to the consumer and
the likely reduced consumption would easily offset any marginal
increase in nutritional properties, even if they did occur, which I
doubt.  To improve public health we need to encourage people
to eat more fruit and vegetables, regardless of how they are
produced.”

Big tip of the hat to
Brad Plumer over at Vox whose links I shamelessly
mined.