Cornell University researchers have found a way to boost what may be whole milk's natural cancer-fighting ability. By making simple changes in the cow's feed, they have substantially increased the amount of conjugated lineoic acid (CLA) -- a cancer-fighting compound -- in the milk.

A number of laboratory studies -- not at Cornell -- have shown that CLA suppresses carcinogens and inhibits proliferation of colon, prostate, ovarian, breast cancers and leukemia. While none of these studies have involved humans, laboratory research indicates that CLA, even in extremely low dietary concentrations (for example, 0.05 percent), inhibits carcinogenesis.

"Most dietary substances exhibiting antic-arcinogenic activity are of plant origin and are only present at trace levels," said Dale Bauman, Cornell professor of animal science who led the work. "However, CLA is found almost exclusively in animal products and is among the most potent of all naturally occurring anti-carcinogens."

Bauman and Miriam L. Kelly, Cornell graduate student in Bauman's lab, from Tyrone, Pa., will present their findings, "Conjugated Lineoic Acid: A Potent Anti-carcinogen Found in Milk Fat," on Wednesday, Oct. 23, at 10:55 a.m. at the Cornell Nutrition Conference for Feed Manufacturers in the Marriott Thruway Hotel, Rochester, N.Y.

The research was funded by the Northeast Dairy Food Research Center, located at Cornell.

Thanks to the cow's digestive system, humans may benefit from drinking milk with increased CLA levels. Dietary fats, such as corn oil, in ruminants are released by microbes in the rumen, the first stomach chamber of four. Newly freed unsaturated fatty acids then undergo biohydrogenation, which combines the unsaturated fats with hydrogen, thanks to rumen bacteria in the later stage of digestion.

The result: With higher levels of unsaturated fats in the feed, the cow makes milk with increased levels of CLA.

"It's clear that dietary and management practices used by dairy producers are resulting in a rumen environment in which biohydrogenation of fatty acids varies so that higher levels of CLA occur," Bauman said. In collaboration with scientists from the University of Idaho, he set out to find out why.

The Cornell research shows a dramatic CLA increase when the diet contains unsaturated fats, such as those contained in corn oil. For example, when only 3 percent dietary fat was fed, only 2 milligrams of CLA per gram of milk fat were found. But when unsaturated fats were doubled, researchers found 4.5 milligrams of CLA per gram of milk fat. When 7.2 percent unsaturated fat was fed, the cow produced 6.9 milligrams of CLA per gram of milk fat.

"The potential exists to identify dietary and management conditions that would increase the CLA concentrations in dairy products," Bauman said. "The novel part of all this is that we're using our knowledge of the dairy cow's digestive and metabolic system to design ruminant diets and practices that enhance CLA levels in milk.

"Milk now provides high-quality protein, energy, calcium, as well as a variety of vitamins and minerals for humans," he said. "This brings an exciting twist to the concept of redesigning foods. If milk is high in CLA, it may provide even greater health benefits: anti-carcinogenic capabilities."