Senior author Dr. Dena Bravata and Dr. Crystal Smith-Spangler, both of Stanford University, said they did not find strong evidence that organic foods were more nutritious, but consumption of organic foods reduced the risk of pesticide exposure.
The popularity of organic products -- generally grown without synthetic pesticides, fertilizers, routine use of antibiotics, growth hormones, or human sludge -- is skyrocketing in the United States, the researchers said.
From 1997 to 2011, U.S. sales of organic foods increased from $3.6 billion to $24.4 billion, the study said.
For the analysis, the researchers identified 237 of the most relevant to analyze including 17 studies -- six of which were randomized clinical trials -- of populations consuming organic and conventional diets and 223 studies that compared either the nutrient levels or the bacterial, fungal or pesticide contamination of various products. There were no long-term studies of health outcomes of people consuming organic versus conventionally produced food -- the duration of the studies involving human subjects ranged from two days to two years.
Although there was no difference in protein or fat content between organic and conventional milk, but studies suggested organic milk might contain significantly higher levels of omega-3 fatty acids.
There are plenty of other reasons to buy organic instead of conventional -- many people said organics taste better and many had concerns about the effects of conventional farming practices on the environment and animal welfare, Bravata said.
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