Sep 07 2010

Organic Food Quality

In my perfect world major societal decisions would be based upon logic and evidence, not ideology. But humans are ideological creatures – we develop belief systems that we jealously defend, and are subject to confirmation bias so that we falsely believe the evidence supports our ideology.

For example, I have never been a fan of organic farming. I have nothing specific against it, however it seems to me that the increasing popularity of organic farming is based largely on ideology (a naturalistic fallacy) than on evidence. I have no dog in that hunt, as they say – no vested interest in organic vs conventional farming at all. I really cannot think of a reason why I would care one way or the other – I simply want what works. Whatever farming methods are the most efficient and sustainable, producing the highest quality and cost-effective food – that’s what I support.

Organic farming is an odd mix of beliefs that are historically based upon the vague notion that “natural” is better. That does not mean that some good ideas have not emerged from the culture of organic farming, and I think if it has anything to offer it is a strong advocacy of sustainable farming. But when I listen to advocates, either personally or in a public forum, they seem to focus on a few specific claims that are rather dubious. I hear a lot about the evils of “big agro” and how organic farming supports small local farmers. However, if you buy organic at your supermarket you are likely buying from a “big agro” company that likes the higher profit margins of organic produce.

But the most common justification I hear for the higher price of organic food is that they are more nutritious. This is perhaps the one aspect of organic food that has the most evidence available to judge. The simple fact is there is no advantage to organic food vs convention food with regard to nutrition. One recent systematic review of published literature looking at nutrient content 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.

Another recent systematic review, looking at health effects (rather than nutrient content) concluded:

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.

So the best evidence we have to date indicates that organic food is neither more nutritious nor more healthful than conventionally grown food. Some people may support organic farming for other reasons, but the evidence does not support claims for nutritional or health superiority. I think the jury is still out regarding effects on the environment, and there is even evidence to suggest that organic farming may be worse for the environment.

But back to food quality – there is a recent study comparing organically grown to conventionally grown strawberries. This is a nice direct comparison. In the abstract the authors conclude:

Our findings show that the organic strawberry farms produced higher quality fruit and that their higher quality soils may have greater microbial functional capability and resilience to stress. These findings justify additional investigations aimed at detecting and quantifying such effects and their interactions.

The second claim seems non-controversial – organic farming methods cultivate a soil microbial system more than conventional methods. This finding is therefore no surprise, although it’s implications are unclear.

But I was struck by the first conclusion – that organic strawberries are “higher quality fruit”. Perhaps for some produce certain organic methods do have advantages – again, I will go wherever the evidence leads. But when I read the actual study I found that the data do not support the authors conclusions. You can look through the tables and decide for yourself how you would summarize the data, but in the body of the paper they report:

Leaf P (phosphorous) and fruit P and K (potassium) concentrations were significantly higher in conventionally grown strawberry plants than in organically grown plants; leaf Mg and fruit N (nitrogen) were also notably higher (P<0.10) in conventionally grown strawberry plants. All other strawberry and leaf nutrient concentrations were similar.

And elsewhere they note:

Organic strawberries had significantly higher total antioxidant activity (8.5% more), ascorbic acid (9.7% more), and total phenolics (10.5% more) than conventional berries, but significantly less phosphorus (13.6% less) and potassium (9.1% less).

So – the conventionally grown strawberries had some advantages, while organic strawberries had others, and otherwise the nutrient content was the same. How does that make organic strawberries superior? You get slightly more of a couple vitamins with organic strawberries, and slightly more minerals with conventional strawberries.  This seems like no significant difference to me.

You also have to consider that they were comparing multiple varieties of organic and conventional strawberries and making multiple comparisons. This looks like a scatter shot of random results from looking at tons of comparisons. There was no consistent pattern of superiority to any variety studied. Again – look through the tables and see for yourself.

They also found that organic strawberries were smaller (not surprising), which also means they were denser and redder. With one variety subjects rated the organic strawberries as more appealing, with another no difference, and with a third they rated the conventional strawberries better. Again – seems like a wash to me, but the authors emphasize that in one variety the organics were rated higher.


I remain unconvinced that there is any advantage to organic farming. This study, if anything, supports the conclusion that there is no significant difference. Organic produce tends to be smaller and denser, and may have slightly higher concentrations of some vitamins (but not significant in terms of nutrition and health), while conventional produce has higher nitrogen and certain minerals. This makes sense based upon the methods of fertilizer used, and is consistent with previous studies. Bottom line – these are minor differences with no real impact on health and nutrition.

But the bigger issue is that organic farming is an eclectic collection of methods grouped together for purely ideological reasons (based largely on the naturalistic fallacy). In my opinion it would be better to judge each farming method on its own merits, based upon the best evidence available.

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