SEATTLE — There's no doubt eating organic food can reduce your exposure to pesticides, but the jury remains out on whether organically grown food is inherently more nutritious than food produced using the full chemical armory of conventional agriculture.
Now, new research from Washington State University concludes that when it comes to milk, the organic variety really does have at least one nutritional advantage.
In the first large-scale study to compare milk from organic and conventional dairies across the United States, the researchers found significantly higher levels of heart-healthy fatty acids in organic milk.
The reason is that organically raised cows eat more grass and less corn and other grain-based feed than their conventional counterparts, said lead author Charles Benbrook, of the university's Center for Sustaining Agriculture and Natural Resources.
"In my judgment, the benefits from this healthy balance of fatty acids in organic milk is the most significant nutritional benefit demonstrated so far for organic food," he said.
Previous studies have suggested that some organic fruits and vegetables contain higher levels of antioxidant chemicals compared with conventional produce. But most major reviews of all the evidence have found little nutritional distinction between organic and conventional foods.
Milk has been the exception, with a few previous studies — particularly in Europe — noting differences in fat composition. The Washington university study, which was partly funded by the organic farm cooperative Organic Valley, is the biggest so far, analyzing nearly 400 samples of whole milk collected over an 18-month period. The results were published Monday in the journal PLoS ONE.
On average, organic milk contained 25 percent fewer of the omega-6 fatty acids common in fried foods, which have been implicated in inflammation, heart disease and diabetes. Organic milk was also 62 percent richer in the omega-3 fatty acids believed to be at least partly responsible for the healthful effects of eating fish, beans and many vegetables.
Both types of fatty acids are essential for health, but many nutrition experts believe the balance in the typical American diet has become skewed because of the heavy use of omega-6-rich corn and soy oils in processed and fast foods.
Most Americans consume 10 to 15 times more omega-6 fatty acids than the healthier omega-3s, Benbrook said.
Drinking whole milk -- whether conventional or organic -- is one way people can help bring those levels back into balance, Benbrook said, with the new results suggesting organic milk as the better choice.
The benefits could be most pronounced among people predisposed to heart disease, young children and women of childbearing age, he added.
But other experts caution that there's no evidence yet that shelling out for more costly organic milk will actually translate into health benefits.
"I'm sure the study is well-done in terms of the analysis," said University of Wisconsin food scientist Scott Rankin, president of the American Dairy Science Association. "But I would want to see a greater ability to connect the dots between this (fatty acid) ratio and some great claims about cardiovascular disease."
Though organic milk may be higher in beneficial fatty acids, the levels are still low, Rankin pointed out. "If you have 60 percent more of a tiny amount, does that have a nutritional implication?" he asked.
An official at the National Dairy Council, an industry association that has until now insisted that there are no significant nutritional differences between organic and conventional milk, said the new data are "very interesting," and worthy of follow-up study.
But Jeff Zachwieja, senior vice president for research, said that instead of switching from conventional to organic milk, a more effective way to improve the fatty-acid balance in your diet would probably be to reduce consumption of foods and oils high in omega-6s.
The study, done in collaboration with researchers from the European Union, analyzed only whole milk. Fatty-acid levels are lower in reduced-fat milk, and any related benefits would be correspondingly smaller, Benbrook said.
But dietary recommendations discourage the consumption of whole milk, to reduce calories and fat and lower levels of "bad" cholesterol associated with heart disease.
Some scientists say people shouldn't be drinking cows' milk at all. A recent viewpoint column in the journal JAMA Pediatrics by researchers from Harvard Medical School pointed out that humans evolved without it, and that there are many other ways to get the calcium needed for bone health.