Thursday, 30 July 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.

No comments:

Post a Comment