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The Department of Agriculture sets stringent guidelines for organic food producers. Certified organic produce, for instance, must be grown without the use of most synthetic pesticides and herbicides. And animal products such as meat, poultry, dairy and eggs must come from animals given year-round access to the outdoors and raised without growth hormones or antibiotics. Organic products can’t use genetic engineering, either. One reason organic foods can be more expensive than their conventional counterparts is that producing them without synthetic pesticides or herbicides requires more labor, said Sean Svette, a dietitian and director of the nutrition and dietetics program at the University of Colorado Colorado Springs.
An organic farmer who doesn’t use a powerful weed-killing herbicide, for instance, may need to hire more workers to remove the weeds. With macronutrients like protein, carbohydrates and fat, there are no differences between organic and nonorganic foods, said Lizzy Davis, an assistant professor of nutrition sciences at the University of Alabama at Birmingham.
Some studies do suggest small differences between micronutrients like vitamins, minerals and certain antioxidants. One study found, for instance, that organic marionberries and corn might contain higher antioxidant levels than their nonorganic counterparts. But these findings have been inconsistent, Dr. Davis said. And researchers haven’t proven that these micronutrient differences are big enough to affect health, she added.
Studies probing organic foods’ long-term health effects have been mixed. In a 2018 study of about 70,000 adults in France, researchers found that those who ate organic food most frequently had 25 percent fewer cancer diagnoses than those who never ate organic food. But several years earlier, a study of about 623,000 middle-aged women in Britain found no difference in cancer rates among organic versus nonorganic eaters.
One explanation for such conflicting findings is that people who consistently eat organic food are more likely to have healthier diets and habits — and higher incomes — than those who eat conventional, Dr. Mathieu said. So we can’t say that the organic foods themselves caused any health results. These studies also rely on people to accurately remember everything they ate over months or years, which is notoriously challenging to do.
标题：纽约时报 |贵好几倍的有机蔬菜，是智商税吗？
