Thursday, July 30, 2009

Nutrition advantages of organic over conventional food

Organic food probably has modest nutrient advantages over conventional food. For example, a literature review in 2008 summarized several hundred matched pairs, where one observation was organic and the other conventional. Organic had more nutrients in 61% of cases, which is notable but not overwhelming.

It is wisest to make your decisions about organic and conventional food primarily based on your assessment of the environmental considerations. The nutrient differences are not as decisive. If you don't care about artificial pesticides or GMOs, you may prefer whichever is less expensive. If you want food grown without artificial pesticides or GMOs, you may prefer organic.

In any case, I would not yet give credence to the much-circulated Reuters report yesterday that organic has no nutrient advantages over conventional food. The report is based on a literature review released yesterday through the American Journal of Clinical Nutrition. The review, funded by the UK Food Standards Agency, had different selection criteria from the earlier research mentioned above.

It seems to me the new UK literature review was not sufficiently powered to detect the small advantages of organic that one might realistically expect. For example, unless there is an error (in tabulation or in my reading), it shows a 10% advantage of organic over conventional in zinc, but the result was not statistically significant (for example, because the sample size was not large enough). The authors say this shows organic is no better than conventional. But, nobody ever expected a greater than 10% advantage for organic anyway. Really, the new results are essentially consistent with the older research. I think the authors err in summarizing their results as refuting the earlier claim that organic food offers slightly more nutrients, and the Reuters report is mistaken in its news summary of this research.

The new study has also been critically covered by Paula Crossfield at Civil Eats and Charles Benbrook at the Organic Center. From Benbrook:
Despite the fact that these three categories of nutrients favored organic foods, and none favored conventionally grown foods, the London-based team concluded that there are no nutritional differences between organically and conventionally grown crops.
I leave this fuss in the same place I started. There are probably modest nutrient advantages from organic production.


Anonymous said...

"There are probably modest nutrient advantages from organic production"

which, in turn, are likely from the increased fertility of the soil as managed under organic systems. Soil health (or, conversely, degradation), whatever the system, is the important variable that will be overlooked in this controversy about which is better.

On-line books on soil:
Building Soils for Better Crops

The Soil Biology Primer

IMO, two other books that deserve much more wide reading are Hillel's "Out of the Earth: Civilization and the Life of the Soil" and Montgomery's "Dirt: The Erosion of Civilizations".

Somehow sometime, a switch focusing on soil health and maximizing it for a given location is crucial.

MAT kinase said...

I'm very skeptical of studies such as this. So many environmental factors impact the chemistry of plants that it appears completely meaningless to arbitrarily choose a number of "organic" plots to be compared to "conventional" plots. Size of the operation, amount of inputs, climate and soil all have critical influences, which I can't imagine many of these studies attempt to control for.

The Almond Doctor said...

Are the benefits really from organic production as a whole or one or two specific practices that are used within organic production. I doubt any nutritional benefits could be derived from differing pest management practices, making me conclude that possible differences arise from the differing fertilization programs. There is something to be said for organic practices that "rebuild" soils, but the work is in progress to tease apart and identify the integral practices.