Conventional milk lacks in some of the fatty acids that contribute to healthy heart present in whole milk from organic diaries, researchers say.
Published in the journal PLOS One, the finding is the most clear-cut instance of an organic food's offering a nutritional advantage over its conventional counterpart.
Other studies looking at organic fruits and vegetables have been deemed less conclusive.
Charles M. Benbrook, a research professor at Washington State University's Center for Sustaining Agriculture and Natural Resources, and the study's lead said: "Drinking whole organic milk will certainly lessen the risk factor for cardiovascular disease."
"All milk is healthy and good for people," he added, "but organic milk is better, because it has a more favorable balance of these fatty acids" - omega-3, typically found in fish and flaxseed, versus omega-6, which is abundant in many fried foods like potato chips.
The government requirements for organic labeling established that dairy cows must spend a certain amount of the time in the pasture, eating grassy plants high in omega-3s; conventional milk comes from cows that are mostly fed corn, which is high in omega-6s. Nonorganic cows that graze in pastures also produce milk with greater amounts of omega-3s.
The present study was funded by Organic Valley, a farm cooperative that sells organic dairy products. But experts not connected with the study said the findings were credible.
"I think this is a very good piece of work," said Dr. Joseph Hibbeln, a nutritional neuroscientist at the National Institutes of Health.
The scientists studied 384 samples of organic and conventional whole milk taken over 18 months around the country. Although the total amount of fat was almost the same, the organic milk contained 62 percent more omega-3 fatty acids and 25 percent fewer omega-6s.
The ratio of omega-6 to omega-3 in the organic milk was 2.28, much lower than the 5.77 ratio in conventional milk. (The figures do not apply to nonfat milk, which strips away the fatty acids.)
