Little Evidence of Health Benefits from Organic Foods

The debate about organic versus nonorganic food has always been a well-contested one with many arguing that organic foods are best for the health.

But now, a Stanford University research claims if you are an adult making a decision based solely on your health, there is not much difference between organic and conventional foods.

The findings were published in the Sept. 4 issue of Annals of Internal Medicine.

Between 1997 and 2011, U.S. sales of organic foods increased from $3.6 billion to $24.4 billion, and many consumers are willing to pay a premium for these products. Organic foods are often twice as expensive as their conventionally grown counterparts.

The popularity of organic products, which are generally grown without synthetic pesticides or fertilizers or routine use of antibiotics or growth hormones, is skyrocketing in the United States. So, senior author Dena Bravata and her team set out if organic foods are more nutritious or carry fewer health risks than conventional alternatives, though consumption of organic foods can reduce the risk of pesticide exposure.

The researchers analyzed 237 previous studies and clinical trials. They consisted of populations consuming organic and conventional diets, and comparison of 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. 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.

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 (and the researchers note that because few people have phosphorous deficiency, 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."

"Some believe that organic food is always healthier and more nutritious," said Smith-Spangler, who is also an instructor of medicine at the School of Medicine. "We were a little surprised that we didn't find that."

The review yielded scant evidence that conventional foods posed greater health risks than organic products. While researchers found that organic produce had a 30 percent lower risk of pesticide contamination 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 generally 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 significance of these findings on child health is unclear. Additionally, organic chicken and pork appeared to reduce exposure to antibiotic-resistant bacteria, but the clinical significance of this is also unclear.

"If you look beyond health effects, there are plenty of other reasons to buy organic instead of conventional," Bravata said. "Our goal was to shed light on what the evidence is," said Smith-Spangler. "This is information that people can use to make their own decisions based on their level of concern about pesticides, their budget and other considerations."

She also said 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.