Like iPods and skinny jeans, organic food is trendy. Even in this cash-strapped economy, more than 70 percent of consumers buy organic food occasionally and nearly one quarter of Americans buy it every week, according to the market research firm the Hartman Group. Considering organic is often priced up to 50 percent more than conventional foods, you have to wonder: Is it really worth the extra cost?
A new Stanford study published into today's Annals of Internal Medicine aimed to answer that question by sifting through 237 published studies comparing organics to conventional foods. Organics, they found, might not be more nutritious but will likely lower your exposure to pesticides and dangerous bacteria.
Conventional and organic produce scored equally on vitamin and mineral content. Only one nutrient — phosphorus — was significantly higher in organic versus conventionally grown produce. There was no difference in protein or fat content between organic and conventional milk, though evidence from a few studies suggested that organic milk may contain significantly higher levels of omega-3 fatty acids.
"Some believe that organic food is always healthier and more nutritious," said lead author Dr. Crystal Smith-Spangler. "We were a little surprised that we didn't find that."
Crops bearing the USDA organic seal of approval are raised without synthetic pesticides, petroleum-based fertilizers, or sewage sludge. Organic animals must be fed organic feed free of antibiotics or growth hormones. Anything labeled organic can't be genetically engineered or treated with radiation to prolong shelf life.
Sticking with organic chicken and pork appeared to limit exposure to antibiotic-resistant bacteria, which some experts warn may be contributing to the rise of hard-to-treat infections in humans. However, not all the organic produce tested was 100 percent pesticide free. While they were 30 percent less likely to have traces of chemicals than conventional fruits and vegetables, Spangler-Smith says that the pesticide levels of all foods fell within allowable safety limits.
But the review didn't gauge the possible long-term effects of pesticide exposure. None of the studies lasted longer than two years – and some lasted as few as two days.
"The risk of a diet without fruits and vegetables is greater to a person's health than the risks posed by pesticide residues," said Dr. Sonya Lunder, a senior research analyst for the non-profit Environmental Working Group, in Washington D.C. "However, for certain populations, most notably pregnant women, young children and the elderly, eating foods with high levels of synthetic pesticides could, over time, cause health problems."
For babies in the womb and young children, Lunder speculates that the most serious risks of long-term pesticide exposure could likely be impaired brain and nervous system development, leading to diminished IQ and ADHD in young children or small birth weight and early births for newborns. In the only study in the review that measured pesticide levels in people, they plummeted to undetectable levels in children on the days they ate organic foods.
The authors concede the paper has other shortcomings as well. Most of the studies they included looked at general "produce" or "meat" categories in the diet. Smith-Spangler said she would have liked to offer head-to-head comparisons for specific food items -- for instance, conventional versus organic plums. Also, since most people in the studies ate a mix of organic and conventional foods, it's nearly impossible to say which health benefits are definitely linked to eating organic.