Much ado about phytochemical differences in organic food claimed in a new report to be of nuritional significance.

State of Science Review: Nutritional Superiority of Organic Foods

by Charles Benbrook, Xin Zhao, Jaime Yáñez, Neal Davies and Preston Andrews
http://www.organic-center.org/reportfiles/5367_Nutrient_Content_SSR_FINAL_V2.pdf
(large file)
March 2008

Key Findings
There were 236 valid matched pairs across the 11 nutrients. The organic foods within these matched pairs were nutritionally superior in 145 matched pairs, or in 61% of the cases, while the conventional foods were more nutrient dense in 87 matched pairs, or 37%. There were no differences in 2% of the matched pairs.
The organic samples contained higher concentrations of the very important polyphenols and antioxidants in about three-quarters of the 59 matched pairs representing those four phytonutrients. Increasing intakes of these nutrients is a vital goal to improve public health since daily intakes of antioxidants and polyphenols are less than one-half of recommended levels.... continues at large pdf file in link


A response to these claims:

Quercetin Content in Organic and Conventional Crops: A Review of the Evidence
Today in AgBioView from* AgBioWorld, Apr. 3, 2008

- Joseph D. Rosen, Emeritus Professor of Food Toxicology, School of Environmental and Biological Sciences, Rutgers University

Charles Benbrook, a consultant for the Organic Trade Association's Organic Center, and his colleagues have published a 53-page report titled "New Evidence Confirms the Nutritional Superiority of Plant-Based Organic Foods". They reviewed the literature for research that compared nutritional differences (quercetin, kaempferol, total phenolics, antioxidant capacity, ascorbic acid, beta-carotene, vitamin E, potassium, phosphorous, nitrate, and total protein) between organically and conventionally grown food. They identified 236 valid matched pairs (on the basis of criteria that they set up) and found, on average, essentially no or very little difference between the two cropping systems for most of the nutrients. The press release heralding this piece of work claimed that one of the largest differences was found in the flavonoid quercetin, where, on average, "the organic foods were 2.4 times more nutrient dense" than the conventional foods.

This claim is based on the results of five peer-reviewed publications that contained 15 valid matched pairs: [Antonnen and Karjalainen, J.Agr. Food Chem 54:7530-7538; Chassy et al., J. Agr. Food Chem 54:8244-8252 (2[0]06); Mitchell et al., J. Agric. Food Chem. 55: 6154-6159 (2007; Ren et al., J. Food Sci. Agric. 81: 1426-1432 (2001); Young et al., Mol. Nutr. Food Res. 49:1136-1142 (2005))].

There was only one valid matched pair in the Antonnen and Karjalainen study and this showed a 5% increase for quercetin in black currants. In Chassy et al., there were 4 matched pairs (two different cultivars of bell peppers and two tomato cultivars). Neither of the bell pepper varieties showed any statistically significant differences between organic and conventional farming practice. Benbrook et al. list a 25% increase in quercetin (3-yr average) for the organically grown Ropreco tomatoes but Chassy et al. did not consider this value statistically significant. The organically grown Burbank cultivar 3-year average for quercetin was 30 % higher than in the conventionally grown and was deemed statistically significant by Chassy et al. despite the fact that the value for the former was 3.42+/-2.64 and the value for the latter was 2.64+/-1.27. The higher average value for the organically-grown Burbank tomatoes was due to a huge (84%) increase in the 2003 growing season. In 2004, there was no statistical difference between the two cropping systems and in 2005 the conventionally grown Burbank tomatoes had statistically significant (17%) more quercetin than the organic tomatoes. Since the studies in these five publications are nowhere near to proving the nutritional superiority of organic food, that leaves ten remaining studies for consideration

Young et al. found no statistically significant differences in quercetin content between organically and conventionally grown collards, Kalura leaf lettuce, Red Sails leaf lettuce and pac choi. Now we're left with six studies.

One of these studies (Mitchell et al.) reported a 79% increase in quercetin content in organic tomatoes over a 10-year period. According to the authors, however, the monoculture practices followed by the farmers who grew these tomatoes are rarely, if ever, followed by organic farmers. So don't expect to see these tomatoes at your local Whole Foods anytime soon, which leaves us with the five valid matched pairs in Ren et al.

Ren et al. did not measure quercetin. Instead they measured quercetrin (a conjugate of quercetin and rhamnose), a fact that escaped Benbrook and his colleagues. (Incidentally, Chassy et al. and Mitchell et al. actually measured quercetin conjugates plus free quercetin because they acidified their extracts, a process that liberated free quercetin from its glycoside conjugates). A more grievous error, however, is using Ren's data altogether. The increases in quercetrin content in the organic vegetables were spectacular: 943 % in Welsh onion, 395% in Chinese cabbage, 136% in quing-gen-quai, 74% in green pepper and 28% in spinach. These increases had nothing to do with organic vs. conventional but had everything to do with the fact that the organic farmer used chitosan (an insect repellent) whenever there were signs of infestation. Chitosan is an inducer of phenyl ammonia-lyase, a key enzyme in the biosynthetic pathway that converts phenyalanine to flavonoids in plants (Khan et al. J. Plant Physiol. 160: 859-863 (2003).