Sales of organic products, which are grown without synthetic pesticides or fertilizers or routine use of antibiotics or growth hormones, are skyrocketing in the United States. Between 1997 and 2011, U.S. sales of organic foods increased from $3.6 billion to $24.4 billion, indicating that many consumers are willing to pay a premium for these products.
But while there is a common perception that organic foods are better for you than non-organic ones, there has been little scientific evidence to support the notion. Now, however, a new study from Stanford University calls into question the supposed health benefits of organic produce.
Researchers led by Dena Bravata, a senior affiliate with Stanford's Center for Health Policy, have completed the most comprehensive meta-analysis to date of existing studies comparing organic and conventional foods. The findings appear in the Annals of Internal Medicine.
For their study, the researchers sifted through thousands of papers and identified 237 of the most relevant to analyze. Those included 17 studies comparing organic and conventional diets, and 223 studies that compared either the nutrient levels or the bacterial, fungal or pesticide contamination of various products (fruits, vegetables, grains, meats, milk, poultry, and eggs) grown organically and conventionally.
After analyzing the data, the researchers found little significant difference in health benefits between organic and conventional foods. No consistent differences were seen in the vitamin content of organic products, and only one nutrient - phosphorus - was significantly higher in organic versus conventionally grown produce (the researchers note that this has little clinical significance).
There was also no difference in protein or fat content between organic and conventional milk, though evidence from a limited number of studies suggested that organic milk may contain significantly higher levels of omega-3 fatty acids.
The researchers were also unable to identify specific fruits and vegetables for which organic appeared the consistently healthier choice, despite running what Bravata called "tons of analyses."
Contaminant-wise, the review yielded scant evidence that conventional foods posed greater health risks than organic products. While the researchers found that organic produce is 30 percent less likely to be contaminated with pesticides than conventional fruits and vegetables, organic foods are not necessarily 100 percent free of pesticides. What's more, as the researchers noted, the pesticide levels of all foods fell within the allowable safety limits. Two studies of children consuming organic and conventional diets did find lower levels of pesticide residues in the urine of children on organic diets, though the levels of urinary pesticides in both groups of children were below the allowable safety thresholds.
As for what the findings mean for consumers, the researchers said their aim is to educate people, not to discourage them from making organic purchases. "There isn't much difference between organic and conventional foods, if you're an adult and making a decision based solely on your health. If you look beyond health effects, there are plenty of other reasons to buy organic instead of conventional," noted Bravata. She listed taste preferences and concerns about the effects of conventional farming practices on the environment and animal welfare as some of the reasons people choose organic products.
Co-researcher Crystal Smith-Spangler added that people should aim for healthier diets overall. She emphasized the importance of eating of fruits and vegetables, "however they are grown," noting that most Americans don't consume the recommended amount.
Discuss this article in our forum
Dietary fiber found to boost healthy gut bacteria
Low-fat dressings hinder nutrient take-up in salads
Popular Food Myths - What's The Truth?
Dietary supplements making people less healthy?
Source: Stanford University Medical Center