A new meta-analysis of 97 published studies shows that organic foods
are on average 25% more nutrient-dense than conventional foods grown in
the same area, on similar soil.1 This study makes it
possible to conclude that organically grown foods are actually more
nutritious than conventionally grown foods.
The new study is a “State of Science Review” published by the
Organic Center, a Colorado-based nonprofit organization whose goal is
to create publications that quantify and explain the benefits of
organic foods to the public. The study is called “New Evidence Confirms
the Nutritional Superiority of Plant-based Organic Foods,” and may be
accessed here.
The co-authors of this study include Charles Benbrook, PhD, Chief
scientist of the Organic Center, Xin Zhao, PhD, an assistant professor
of Horticultural Science at the University of Florida, Gainesville, and
the other three co-authors are all associated with Washington State
University: Jaime Yáñez, PhD, a senior scientist, Neal Davies, PhD,
RPh, a clinical pharmacist and associate professor, College of
Pharmacy; and Preston Andrews, an associate professor in Horticultural
Science.2 Popular author and integrative medicine pioneer
Andrew Weil, MD, an ABC Advisory Board Member, wrote the foreword for
this study.
After the analysis of 97 studies, which involved 135 study-crop
combinations, 94 crop-study combinations were found “high quality” in
terms of experimental design, and 41 were found invalid, according to
the criteria determined by the co-authors. After further examining the
94 valid study-crop combinations in terms of the validity of their
analytical methods, 55 matched pairs of an organic crop and
conventional crop were deemed invalid for a specific nutrient. Out of
the 94 valid study-crop combinations, 236 valid matched pairs for a
specific nutrient of organic and conventional foods were found and then
compared for their nutritional value. The reason for the much higher
number of matched pairs than valid study-crop combinations is that some
studies reported results for multiple nutrients for a given matched
pair.
Organic foods were found to be more nutritious overall by, on
average, 25%. This was calculated by averaging the difference in 11 key
nutrients between conventional and organic foods in each of the matched
pairs, where organic food was superior in 145 of the matched pairs and
conventional only 87 of the matched pairs.1
A possible reason for the nutritional superiority of organic food is
that on organic farms, crop yields in relation to the number of plants
per acre are somewhat lower and plants develop more slowly. According
to Dr. Benbrook, the main writer of the study, when a plant grows
slower it has more time to absorb the nutrients in the soil (oral
communication, April 18, 2008). More conventionally grown plants tend
to have an accelerated growth time so farmers can reach aggressive
yield goals. “Conventional fruit and vegetable crops produce food that
contains elevated levels of water, sugars, and nitrates,” Benbrook
said. “This is called nutrient dilution.”
This meta-analysis was initiated in 2006 and concluded in March 2008
after the writing of the study; however, Benbrook said the co-authors
plan to add the results of about 10 more studies to their database and
produce a new publishable study to submit to a scientific journal. They
also plan to begin a new study that involves animal products and
animal-based foods. This study would compare organically fed and
conventionally fed animals while examining such factors such as
unsaturated and saturated fat, heart-healthy fat, Omega 3s and 16s,
proteins, vitamin A, iron, milk, etc.
—Kelly E. Saxton
References
1New evidence settles a lingering question-is organic
food more nutritious [press release]? Boulder, Colo.: the Organic
Center; March 19, 2008.
2The Organic Center. The State of Science Nutritional Quality page. The Organic Center Web site. Available at http://www.organic-center.org/science.nutri.php?action=view&report_id=126. Accessed March 30, 2008.
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