Organic Food Not Proven Healthier or Safer, Study Finds
By Helena Bottemiller on September 5, 2012
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.”
我们知道它通常花费更多，但是有机肉类和生产更健康 - 或更安全?对科学的新评论表明答案可能是否定的。
根据斯坦福大学科学家进行的一项研究，1997年美国有机物市场价值37亿美元。到2010年，它已膨胀至267亿美元。但该研究质疑，对于经过认证的有机食品 - 无需合成杀虫剂，肥料，抗生素，添加激素或基因工程成分 - 种植和加工的食品是否非常值得。
当涉及细菌污染和生产时，审查人员发现大肠杆菌污染率没有统计学上的显着差异 - 有机污染物为7%，传统污染物为6% - 但审查指出，只有五项研究表明直接回顾比较这种类型的污染。当作者删除一项仅研究生菜的研究时，荟萃分析显示有机农产品的污染风险增加了5%。
对于鸡肉，67%的有机样品和64%的常规样品被弯曲杆菌污染，而35%的有机样品和34%的常规样品被沙门氏菌污染。猪肉通常被大肠杆菌污染 - 65%的有机物和49%的常规样品 - 并且没有找到任何比较有机牛肉和传统牛肉的研究。
该研究发现的一个主要差异是传统动物产品更容易受到对三种或更多抗生素产生抗药性的病原体的污染 - 对于鸡肉和猪肉，常规样品的风险增加33%。当观察对氨苄青霉素的耐药性时，差异最大 - 有机和鸡肉的抗药性风险降低了35% - 但是当观察剩余的抗生素时，传统产品的风险更大。然而，审查发现差异在统计上无关紧要。评价者还指出，他们研究的研究中很少有人对同一种动物产品中的抗生素进行了分析。
互联网一直对这项研究反应迟钝。周二，超过500篇新闻报道 - 标题为“研究问题有机肉和农产品的优势”(纽约时报)，“有机物不是更健康的食物选择，研究发现”(芝加哥太阳时报)，“为什么有机食品对你来说可能不健康“(NPR) - 似乎与越来越多的消费者选择购买有机食品的主要原因相矛盾。
对于主要食用有机食品的人与主要食用传统食品的人相比，没有长期的健康结果研究 - 正如评论者指出的那样，这类研究费用昂贵且难以进行 - 并且可用的研究差异很大在设计，尺寸和范围上，因此难以得出广泛的结论。