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Stanford Scientists Cast Doubt on Advantages of Organic Meat and Produce

Does an organic strawberry contain more vitamin C than a conventional one?


Maybe — or maybe not.


Stanford University scientists have weighed in on the “maybe not” side of the debate after an extensive examination of four decades of research comparing organic and conventional foods.

过去40多年中,大量针对有机食物与普通食物的比较研究陆续问世。在对这些研究进行全面检验评估后,斯坦福大学(Stanford University)的科学家们站到了宁可信其无的这一阵营。

They concluded that fruits and vegetables labeled organic were, on average, no more nutritious than their conventional counterparts, which tend to be far less expensive. Nor were they any less likely to be contaminated by dangerous bacteria like E. coli.


The researchers also found no obvious health advantages to organic meats.


Conventional fruits and vegetables did have more pesticide residue, but the levels were almost always under the allowed safety limits, the scientists said. The Environmental Protection Agency sets the limits at levels that it says do not harm humans.

科学家指出,普通水果蔬菜的确含有更高的农药残留,但大多数情况下并未超过标准允许的安全范围。制定标准的美国国家环境保护局(The Environmental Protection Agency)宣称,该范围内的农药残留不会对人体造成危害。

“When we began this project, we thought that there would likely be some findings that would support the superiority of organics over conventional food,” said Dr. Dena Bravata, a senior affiliate with Stanford’s Center for Health Policy and the senior author of the paper, which appears in Tuesday’s issue of the Annals of Internal Medicine. “I think we were definitely surprised.”

“项目开始时,我们本以为会发现一些支持有机食品优越性的结果,”斯坦福大学卫生政策中心资深研究员德娜·布拉瓦塔(Dena Bravata)博士表示。“可想而知,我们都十分吃惊。”布拉瓦塔是上周二发表于《内科学年鉴》(Annals of Internal Medicine)的该篇论文的资深作者。

The conclusions will almost certainly fuel the debate over whether organic foods are a smart choice for healthier living or a marketing tool that gulls people into overpaying. The production of organic food is governed by a raft of regulations that generally prohibit the use of synthetic pesticides, hormones and additives.


The organic produce market in the United States has grown quickly, up 12 percent last year, to $12.4 billion, compared with 2010, according to the Organic Trade Association. Organic meat has a smaller share of the American market, at $538 million last year, the trade group said.

美国的有机产品市场发展迅猛。来自有机贸易协会(Organic Trade Association)的数据显示,与2010年相比,2011年一年的增长幅度高达12%,市场总额约为124亿美元。该协会表示,有机肉类在美国市场上相对份额较小,去年的市场总额为5.38亿美元。

The findings seem unlikely to sway many fans of organic food. Advocates for organic farming said the Stanford researchers failed to appreciate the differences they did find between the two types of food — differences that validated the reasons people usually cite for buying organic. Organic produce, as expected, was much less likely to retain traces of pesticides.


Organic chicken and pork were less likely to be contaminated by antibiotic-resistant bacteria.


“Those are the big motivators for the organic consumer,” said Christine Bushway, the executive director of the trade association.

 “这些才是有机产品消费者的主要动机,”有机贸易协会执行主任克里斯蒂娜·布什韦(Christine Bushway)指出。

The study also found that organic milk contained more omega-3 fatty acids, which are considered beneficial for the heart.


“We feel organic food is living up to its promise,” said Sonya Lunder, a senior analyst with the Environmental Working Group, which publishes lists highlighting the fruits and vegetables with the lowest and highest amounts of pesticide residues.

“我们觉得有机食品信守了其承诺,”环境工作组(Environmental Working Group)的资深分析师索尼娅·伦德(Sonya Lunder)表示。该组织发布名单,重点列出农药残留量最低的水果和蔬菜。

The Stanford researchers said that by providing an objective review of the current science of organic foods, their goal was to allow people to make informed choices.


In the study — known as a meta-analysis, in which previous findings are aggregated but no new laboratory work is conducted — researchers combined data from 237 studies, examining a wide variety of fruits, vegetables and meats. For four years, they performed statistical analyses looking for signs of health benefits from adding organic foods to the diet.


The researchers did not use any outside financing for their research. “I really wanted us to have no perception of bias,” Dr. Bravata said.


One finding of the study was that organic produce, over all, contained higher levels of phosphorus than conventional produce. But because almost everyone gets adequate phosphorus from a wide variety of foods, they said, the higher levels in the organic produce are unlikely to confer any health benefit.


The organic produce also contained more compounds known as phenols, believed to help prevent cancer, than conventional produce. While the difference was statistically significant, the size of the difference varied widely from study to study, and the data was based on the testing of small numbers of samples. “I interpret that result with caution,” Dr. Bravata said.


Other variables, like ripeness, had a greater influence on nutrient content. Thus, a lush peach grown with the use of pesticides could easily contain more vitamins than an unripe organic one.


The study’s conclusions about pesticides did seem likely to please organic food customers. Over all, the Stanford researchers concluded that 38 percent of conventional produce tested in the studies contained detectable residues, compared with 7 percent for the organic produce. (Even produce grown organically can be tainted by pesticides wafting over from a neighboring field or during processing and transport.) They also noted a couple of studies that showed that children who ate organic produce had fewer pesticide traces in their urine.


Dr. Bravata agreed that people bought organic food for a variety of reasons — concerns about the effects of pesticides on young children, the environmental impact of large-scale conventional farming and the potential public health threat if antibiotic-resistant bacterial genes jumped to human pathogens. “Those are perfectly valid,” she said.


The analysis also did not take factors like taste into account.


But if the choice were based mainly on the hope that organic foods would provide more nutrients, “I would say there is not robust evidence to choose one or the other,” Dr. Bravata said.


The argument that organic produce is more nutritious “has never been major driver” in why people choose to pay more, said Ms. Lunder, the Environmental Working Group analyst.


Rather, the motivation is to reduce exposure to pesticides, especially for pregnant women and their young children. Organic food advocates point to, for example, three studies published last year, by scientists at Columbia University, the University of California, Berkeley, and Mount Sinai Hospital in Manhattan. The studies identified pregnant women exposed to higher amounts of pesticides known as organophosphates and then followed their children for years. In elementary school, those children had, on average, I.Q.’s several points lower than those of their peers.

相反,减少农药暴露才是真正的驱动力,尤其是对于怀孕女性和婴幼儿。推崇有机食物的人指出,哥伦比亚大学(Columbia University)、加州大学伯克利分校(University of California, Berkeley)和曼哈顿西奈山医院(Mount Sinai Hospital)的科学家去年分别发表的三项研究就是证据。这些研究找到那些怀孕期间接触过较高剂量的有机磷酸酯类农药的女性,并对她们生下的孩子进行了数年的跟踪调查。上小学时,这些孩子的智商要比其他孩子平均低好几分。