RODALE NEWS, EMMAUS, PA—There are lots of reasons to shell out a few extra bucks for organic milk: Organically raised cows aren't doused with synthetic growth hormones, nor are they treated with unnecessary antibiotics (did you know that 70 percent of the antibiotics in this country are used on livestock?). They also aren't raised in huge, polluting concentrated animal-feeding operations. And according to a new study, organic cows produce milk that may ward off heart disease.
THE DETAILS: Published in the American Journal of Clinical Nutrition, the study included 3,623 adults from Costa Rica, where cattle are more commonly raised on grass rather than on grain than they are in the U.S. Half of the adults had suffered one nonfatal heart attack, while the other half were healthy. The researchers collected information on diet and physical activity, and they took samples of adipose tissue that they later analyzed for a fatty acid found primarily in dairy products called conjugated linoleic acid (CLA). Levels of CLA are higher in milk from grass-fed cows, says the study's lead author Hannia Campos, PhD, senior lecturer in the department of nutrition at Harvard School of Public Health. "With grass-fed cows, their stomachs maintain the right acidity for enzymes [that produce CLA] to work normally," she says. "But when they're fed corn, the corn increases the acidity of their stomachs, so enzymes in their gut don't work properly."
People who had the highest concentrations of CLA in their tissue had a 36 percent lower risk for heart attacks than people with the lowest concentrations, even after the researchers took into account other lifestyle behaviors, such as smoking and alcohol intake, and family history of the disease.
WHAT IT MEANS: Prior studies have found that milk from grass-fed cows can contain as much as five times more CLA than conventional milk, and Campos says the protective effects of CLA are high enough to offset the harms of saturated fat in milk, even whole milk. "We looked at the effects of dairy intake on cholesterol [which raises with saturated fat intake] to see if we could explain our results, but we didn't see any correlation," she adds. Whole milk has the highest levels of CLA, because "CLA is a type of fat," she says, "so when you start removing fat, you start removing the CLA." Fortunately, she says, grass-fed milk has lower levels of saturated fat than conventional milk (for instance, whole grass-fed milk has less saturated fat than whole conventional milk), so you can still get the benefits of CLA, which is a polyunsaturated fatty acid, even if you want to watch your saturated-fat intake.