July 30, 2009 — Organically grown foods are no more nutritious than conventionally grown foods when it comes to the amount of some important nutrients, according to a new review of published studies.
“We wanted to answer the question, ‘Is there any evidence that organic foods are nutritionally superior to conventionally grown foods?'” says the study’s lead author, Alan D. Dangour, PhD, public health nutritionist at the London School of Hygiene & Tropical Medicine. “The answer is no. Organic foods are not nutritionally superior to conventional foods.”
The findings of the review, published in the American Journal of Clinical Nutrition, elicited strong disagreement from American food researchers.
The global organic food market is estimated at around $48 billion a year, according to the London researchers. Organic foods are produced under standards that control the use of chemicals in crop production and drugs in animal production, among other regulations.
Organic vs Conventional Foods: A Review
Dangour and his colleagues searched for studies comparing organic and conventional foods from January 1958 to February 2008.
They found 55 studies of satisfactory quality to include in their review and assessed several nutrient categories, including:
• Nitrogen
• Vitamin C
• Phenolic compounds (also called polyphenols)
• Magnesium
• Calcium
• Phosphorus
• Potassium
• Zinc
• Total Soluble Solids
• The copper
• Acidity content
They found that conventionally produced crops had higher nitrogen content, while organically produced crops had higher phosphorus and acidity content. No differences were detected for the other nutrient categories of the analyzed crops. When they only looked at animal foods, the researchers found no difference in nutrient content.
The review, funded by the UK’s Food Standards Agency, did not look at differences in pesticide residues between the two growing methods.
Organic versus conventional: other points of view
Officials from the US organic food industry, unsurprisingly, strongly opposed the review, as did other experts.
“Our position is that there is no scientific doubt that organic foods are higher in important vitamins and trace minerals and contain far fewer toxic residues,” says Ronnie Cummins, National Director of Organ Consumers ‘ Association. “And that’s why millions of American consumers pay a high price for organic production.”
One problem with the new review is the use of older studies, some from 1958, says Michael Hansen, PhD, senior scientist at Consumers Union and food safety expert. “More recent studies have clearly shown significant differences between organic and non-organic when it comes to nutrient content,” he told WebMD.
“Most studies published before 1980 are flawed for a number of reasons,” he says, including flawed methodology.
Nutrients in the entire food supply are declining, Hansen says, citing another reason for not grouping the 1958 studies with more recent studies.
But Dangour responds that the criticism is unfounded because the comparisons between organic and conventionally grown foods were made in individual studies. And, he says, “the majority of studies [reviewed] have been published since 2000.”
Charles Benbrook, PhD, chief scientist for The Organic Center, a Boulder-based industry group, says his center’s research has produced different conclusions. “The most contemporary and higher quality studies clearly support the nutritional benefits of organically grown foods over conventionally grown foods,” he says.
He criticizes what he calls a lack of attention to polyphenols and antioxidants, which he says are about 25% higher in organically grown foods. The London team “downplays” the differences they found between the foods, he says.
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