Organic meat and milk differ markedly from their conventionally produced counterparts in measures of certain nutrients, a review of scientific studies reported on Tuesday.

周二（2月9日），一项科学研究综述报告，有机肉类和牛奶在某些营养成分上与通过常规方式生产的同类产品间存在明显差异。

In particular, levels of omega-3 fatty acids, beneficial for lowering the risk of heart disease, were 50 percent higher in the organic versions.

尤其是，有机产品中有益于降低心脏病风险的ω-3脂肪酸的水平比普通产品高出50%。

“The fatty acid composition is definitely better,” said Carlo Leifert, a professor of ecological agriculture at Newcastle University in England and the leader of an international team of scientists who performed the review.

该综述由一国际科学家小组完成，其负责人，英格兰纽卡斯尔大学(Newcastle University)的生态农业教授卡洛·莱费特(Carlo Leifert)说：“（有机产品的）脂肪酸组成绝对更佳。”

The European Commission, the executive body of the European Union, and the Sheepdrove Trust, a British charity that supports organic farming research, paid for the analysis, which cost about $600,000.

该项分析耗资约60万美元，这些费用由欧盟(European Union)的执行机构欧盟委员会(European Commission)和支持有机农业研究的英国慈善机构Sheepdrove Trust承担。

However, the question of whether these differences are likely to translate to better health in people who eat organic meat and drink organic milk is sharply disputed.

然而，上述差异是否代表着吃有机肉类、喝有机牛奶的人更为健康呢？人们对此仍有尖锐的争议。

“We don’t have that answer right now,” said Richard P. Bazinet, a professor of nutritional sciences at the University of Toronto who was not involved with the research. “Based on the composition, it looks like they should be better for us.”

“这个问题的答案我们现在还不得而知，”多伦多大学(University of Toronto)的营养科学教授理查德·P·巴齐内(Richard P. Bazinet)说，他没有参与上述研究。“但就营养组成而言，它们（有机产品）似乎更为有益。”

The two new scientific papers, published in The British Journal of Nutrition, are not the result of any new experiments, but instead employ a statistical technique called meta-analysis that attempts to pull robust conclusions out of many disparate studies.

这两篇新的科学论文发表在《英国营养学杂志》(The British Journal of Nutrition)上，它们并没有介绍什么新的实验结果，而是采用了一种名为荟萃分析的统计技术，试图从众多不同的研究中得出强有力的结论。

They are certain to further stir a combative debate over whether organic foods are healthier. Some scientists assert that organic and conventional foods are nutritionally indistinguishable, and others find significant benefits to organic. Many people who buy organic food say they do so not for a nutritional advantage, but because of environmental concerns and to avoid pesticides.

它们势必会进一步激起人们就有机食品是否更为健康展开激烈的辩论。一些科学家宣称，有机食品和常规食品的营养价值并无区别，而其他人则发现有机产品显著较好。许多人称自己购买有机食品并非是为了更高的营养价值，而是出于对环境的忧虑，以及希望能避免农药问题。

The higher levels of omega-3, a type of polyunsaturated fat, arise not from the attributes usually associated with organic food — that the animals are not given antibiotics, hormones or genetically modified feed — but rather from a requirement that animals raised organically spend time outside. Organic milk and beef come from cattle that graze on grass, while most conventional milk and beef come from cows subsisting on grain.

ω-3脂肪酸是一种多不饱和脂肪。有机食品中ω-3脂肪酸水平较高，并不是有机食品本身的特点（即不给予动物抗生素、激素或转基因饲料）造成的，而是因为有机养殖的动物在室外活动的时间较长。有机牛奶和牛肉产自在草地上放牧的牛，而大多数普通牛奶和牛肉则产自吃谷物的牛。

“It’s not something magical about organic,” said Charles M. Benbrook, an organic industry consultant who is an author of the studies. “It’s about what the animals are being fed.”

“有机食品本身并没有什么神奇之处，”研究的作者之一，有机产业顾问查尔斯·M·本布鲁克(Charles M. Benbrook)说。“关键在于动物是用什么东西饲喂的。”

Most of the same changes would be observed in conventionally raised animals that also grazed for the majority of their diet, the scientists said.“For once, this is a pretty simple story,” Dr. Benbrook said.

科学家们表示，如果常规饲养的动物也以吃草为主，那么在它们身上也能发现很多相同的改变。“这样一来，问题就变得简单了，“本布鲁克博士说。

The review of comparisons of organic and conventional milk analyzed all 196 papers the scientists found. Because studies of meat are sparser, they could not look at just one type of meat like beef or pork. Instead, they did one analysis of the 67 papers they found for all types of meat. “Only if you throw them all in one pot can you do a meta-analysis,” Dr. Leifert said.

科学家们在比较有机和常规牛奶的综述中分析了他们所能找到的所有196篇论文。由于对肉类的研究较少，他们发现只审查关于某一种肉，如牛肉或猪肉的研究不现实。反之，他们对关于各种肉的67篇论文统一进行了分析。“只有把它们放在一起才能进行荟萃分析，”莱费特博士解释道。

Two years ago, Dr. Leifert led a similar review for fruits and vegetables that found organic produce had higher levels of some antioxidants and less pesticide residue than conventionally grown crops.

两年前，莱费特博士领导了一项关于水果和蔬菜的类似综述，发现与用常规方法种植的作物相比，有机农产品中某些抗氧化剂的水平较高，农药残留较少。

Nutrition experts broadly agree that omega-3 fatty acids in food offer numerous health benefits. When the United States Department of Agriculture revised its dietary guidelines in 2010, it urged people to eat more seafood, which is rich in omega-3.

营养专家普遍认同，食物中的ω-3脂肪酸具有多种健康效益。美国农业部(United States Department of Agriculture)在2010年修订其膳食指南时，呼吁人们多多食用富含ω-3脂肪酸的海产品。

Omega-3 is much more prevalent in grass than in grain, which is why organic livestock and milk also contain higher levels. “Lo and behold, we altered in some fundamental ways the nutrient intake of these animals and hence the nutrient composition of the products that we derive from those animals,” Dr. Benbrook said.

草料中的ω-3脂肪酸含量比谷物中高，因此有机家畜及其乳制品中也含有较高水平的ω-3脂肪酸。“你瞧，我们改变了这些动物摄入营养的基本方式，这才影响了其衍生产品的营养成分，”本布鲁克博士说。

The new analysis found that levels of another polyunsaturated fat, omega-6, were slightly lower in organic meat and dairy. Omega-3 and omega-6 are essential for the functioning of the human body, which can make neither. But some have argued that a skewing toward omega-6 has become unhealthy.

新的分析还发现，在有机肉类和乳制品中，另一种多不饱和脂肪酸：ω-6脂肪酸的水平略低。ω-3和ω-6脂肪酸对于人体的正常功能来说都必不可少，而且人体无法自己合成它们。但也有人认为，过多摄入ω-6脂肪酸并不利于健康。

Centuries ago, people ate roughly equal amounts of the two fatty acids. Today, most Americans eat more than 10 times as much omega-6, which is prevalent in certain vegetable oils and thus also fried foods, as omega-3.

几个世纪以前，人们摄入的这两种脂肪酸大致等量。今天，由于某些植物油中普遍含有ω-6脂肪酸（因此油炸食品也一样），大多数美国人摄入的ω-6脂肪酸约为ω-3的10倍以上。

In an email, Dr. Walter C. Willett, the chairman of the nutrition department at the Harvard T.H. Chan School of Public Health, said the differences between organic and conventional beef were trivial, and the amount of saturated fat in both were high.

哈佛大学公共卫生学院(Harvard School of Public Health)的营养系主任沃尔特·C·威利特(Walter C. Willett)博士在一封电子邮件中写道，有机和常规牛肉之间的差异微不足道，而且两者中的饱和脂肪含量均很高。

“Far greater, and beneficial, differences in fatty acids are seen if poultry and fish replace red meat,” Dr. Willett said.

“如果用禽肉和鱼肉来代替红肉，你会发现更大、更有益于健康的脂肪酸差异，”威利特博士如是说。

A shortcoming of the recommendation to eat more fish is that if everyone followed it, the rivers, oceans and lakes would be emptied of fish. Dr. Bazinet of the University of Toronto said perhaps encouraging people to switch to organic meats and milk would be “a way to kind of get at them with the foods they’re already eating.”

不过，多吃鱼这个建议本身也有其缺点：如果每个人都遵循这个建议，那么河流、海洋和湖泊中的鱼就要被吃光了。多伦多大学的巴齐内博士表示，鼓励人们改吃有机肉类和牛奶或许“只是在教人摄入本来就在吃的食物”。

Dr. Bazinet said observational studies suggested that adding 200 milligrams a day of omega-3s to an average diet should yield health benefits. Switching to organic beef would add about 50 milligrams. “Eating one grass-fed beef serving per day is not going to do it,” he said.

巴齐内博士说，观察研究表明，在普通膳食的基础上，每天增加摄入200毫克ω-3脂肪酸可带来健康效益。而改吃有机牛肉只能多摄取到约50毫克的ω-3脂肪酸。于是他总结道：“每天吃一份草饲牛肉达不到你（补充ω-3脂肪酸）的目的。”

But if combined with a couple of glasses of organic milk, “it should make a difference,” Dr. Bazinet said. “That would be the hypothesis.”

但是，如果再喝上一两杯有机牛奶的话，“应该就有用了，”巴齐内博士说。“假设上是如此。”

Scientists are now trying to examine the health question more directly.

现在科学家们正试图以更直接的方式来探讨这些健康问题。

Dr. Leifert cited several studies that indicated that infants of mothers who ate organic fruits and vegetables were less likely to contract some diseases. He is also conducting experiments to see if rats fed organic foods are healthier. So far, he said, it appears that crop pesticide residue does have measurable effects on the rats’ hormones.

莱费特博士列举了数项研究，它们都表明，食用有机水果和蔬菜的母亲所诞下的婴儿较不容易患某些疾病。他还在进行实验，以研究饲喂有机食品的大鼠是否更健康。他说，从迄今为止的结果来看，农作物上的农药残留确实对大鼠的激素水平造成了明显的影响。

“We still don’t know whether it kills you, but we do know it has an effect on hormonal balances,” he said. “It’s something that makes you think a little bit.”

“虽然尚不清楚它是否会致死，但我们的确发现，它会影响激素的平衡。”他说，“这一点颇值得深思。”