We know it usually costs more, but is organic meat and produce any healthier — or safer? A new review of the science suggests that the answer may be no.
According to a study, conducted by scientists at Stanford, the market for organics in the United States was worth $3.7 billion in 1997. By 2010, it had ballooned to $26.7 billion. But the study questions whether paying a premium for certified organic — food grown and processed without synthetic pesticides, fertilizers, antibiotics, added hormones or genetically engineered ingredients — is really worth it.
“Consumers purchase organic foods for many reasons,” wrote the scientists. “Despite the widespread perception that organically produced foods are more nutritious than conventional alternatives, we did not find robust evidence to support this perception.”
The study, published this month in the Annals of Internal Medicine, analyzed 17 human studies and 223 studies on nutrient density and contamination levels and concluded that, so far, published literature “lacks strong evidence” that organic foods are significantly more nutritious, but choosing to consume those foods may reduce exposure to pesticides and antibiotic-resistant bacteria.
The review found that, overall, organic produce is 30 percent less likely to contain detectable pesticides, compared to conventional produce, but the vast majority of all produce tested fell below government safety tolerances. The study did look at one study which found that children who switched to an organic diet for five days had lower levels of pesticides in their urine, but whether the levels have a direct impact on human health is “unclear.”
When it came to bacterial contamination and produce, the reviewers found that there was not a statistically significant difference in the rate of E. coli contamination — 7 percent for organic, 6 percent for conventional — but the review noted that only five of the studies they reviewed directly compared this type of contamination. When the authors removed one study that looked only at lettuce, the meta-analysis showed that organic produce had a 5 percent greater risk for contamination.
Both organic and conventional animal products, on the other hand, have repeatedly been shown to be widely contaminated with harmful pathogens. The reviewers found that the differences in contamination between organic and conventional products were statistically insignificant.
For chicken, 67 percent of organic samples and 64 percent of conventional samples were contaminated with Campylobacter, while 35 percent of organic and 34 percent conventional samples were found to be contaminated with Salmonella. Pork was commonly contaminated with E.coli — 65 percent of organic and 49 percent of conventional samples — and the reviewed did not find any studies that compared organic and conventional beef.
The one major difference the study found was that conventional animal products were more likely to be contaminated with pathogens that were resistant to three or more antibiotics — for chicken and pork conventional samples were 33 percent more at risk. The differences were strongest when looking at resistance to ampicillin — organic and chicken had a 35 percent lower risk for resistance — but when looking at the remaining antibiotics, conventional products were more at risk. However, the review found differences were statistically insignificant. The reviewers also noted that few of the studies they looked at analyzed the same antibiotics on the same animal product.
“This increased prevalence of antibiotic resistance may be related to the routine use of antibiotics in conventional animal husbandry,” wrote the authors. “However, the extent to which antibiotic use for livestock contributes to antibiotic-resistant pathogens in humans continues to be debated because inappropriate use of antibiotics is the major cause of antibiotic-resistant infections in humans.”
The internet has been abuzz with reaction to the study. On Tuesday, more than 500 news stories — with headlines like “Study Questions Advantages of Organic Meat and Produce” (New York Times), “Organics not a healthier food choice, study finds” (Chicago Sun-Times), “Why Organic Foods May Not Be Healthier For You” (NPR) — seemed to contradict one of the main reason a growing number of consumers choose to buy organic.
The authors of the review said their results should be “interpreted with caution.”
There have been no long-term studies of health outcomes for people who eat primarily organic food versus those who eat primarily conventional — as the reviewers note, this type of study would be expensive and hard to conduct — and the studies that are available vary greatly in their design, size and scope, so drawing broad conclusions is difficult.
Still, their meta-analysis of the science to date shows organic produce and meat might not be worth the extra buck to consumers looking for a health benefit.
In an interview Tuesday, Michael Pollan, one of the key figures of the food movement, responded to the study by pointing out that the whole point of organic food is that it’s more environmentally sustainable. “That’s the stronger and easier case to make,” he told KQED.
“I would just encourage people to educate themselves and not take headlines at face value. It’s a complicated question, and we need to a do a lot more science,” he said. “The absence of proof means that we either haven’t studied it or we haven’t found it yet, it doesn’t mean we won’t. In the meantime, there’s a precautionary principle: even though the case isn’t closed on low levels of pesticides in our diet, there are very good reasons to minimize them.”
This story has been updated with links.