"There's really no debate around the world -- when you feed dairy cows more grass, you improve the fatty acid profile of milk. You also increase the protein level," [study author Charles] Benbrook says. On the other hand, cows fed a corn-based diet produce milk that's higher in omega-6 fatty acids.
The reason organic milk is healthier comes down to its ratio of omega-6 to omega-3 fatty acids, which is lower than in regular milk. A diet containing too many omega-6 fatty acids and not enough omega-3s has been linked to heart disease, as well as cancer, inflammation and autoimmune diseases. That's because your gut converts omega-6s to arachidonic acid, which can cause inflammation. But the anti-inflammatory powers of omega-3s help to counterbalance that reaction, which is why keeping that ratio low is so important. (An omega-6 to omega-3 ratio of 2.3 to 1 is best for heart health, research suggests.)
"It's true that both omega 6s and omega 3s are essential – we have to have some of them," Benbrook says. "But it's when they get out of balance, the adverse health effects appear to kick in."
If organic milk is out of your budget, conventional milk is still OK – but choose whole milk, rather than skim or 2 percent. "The heart-healthy fatty acids in milk are part of milk's overall fat content," Benbrook says. "This benefit will be reduced about 50 percent when people choose 2 percent fat milk, and by about two-thirds when purchasing skim or low-fat dairy products."
Even if you don't consume dairy, Benbrook says the larger message here is to try to cut back on foods that are very high in soybean or corn oil, both of which have high omega-6 to omega-3 ratios – things like fried foods, or chips.
Image: Glass of milk, via Shutterstock