Butter made from milk containing increased levels of a natural fatty acid reduced the risk of breast cancer in laboratory animals, according to new research published today (Nov. 25, 1999).
While pubescent rats were used in the experiments, the laboratory animal model suggests that the fatty acid, called conjugated linoleic acid, or CLA, could be beneficial in reducing the risk of breast cancer in women, says Clement Ip, a researcher at the Roswell Park Cancer Institute, Buffalo, N.Y., and the lead author on the research paper.
"This research demonstrates for the first time that natural CLA in foods is biologically active and that we can use a designer-foods concept to enhance the natural level of anti-carcinogens in foods," says Dale E. Bauman, Liberty Hyde Bailey Professor of animal science at Cornell University and another of the paper's authors.
The study appears in the December issue of the Journal of Nutrition, a peer-reviewed journal published by the American Society for Nutritional Sciences. The study was performed by researchers at Cornell; Roswell Park; AMC Cancer Research Center, Denver; and Cittadella Universitaria, Cagliari, Italy. It was supported by grants from the National Dairy Council, Kraft Foods Inc., the National Cancer Institute, the National Institutes of Health, and the Department of Defense. Additional support also was received from the Northeast Dairy Foods Research Center at Cornell.
The journal study reports that high levels of CLA in cow's milk and dairy products, like cheese and butter, reduced the incidence and number of mammary tumors. Indeed, only 50 percent of the animals fed with the CLA butter developed mammary tumors when given high doses of carcinogens. By comparison, 93 percent of the animals who were fed a standard diet not high in CLA developed breast tumors when given the same high amounts of carcinogens. In addition, the CLA butter was shown to reduce the population of mammary terminal end bud (TEB) cells, the cells that are the primary targets for attack by carcinogens, by 30 percent. The CLA also was shown to decrease the TEB cells' proliferation, that is the rate at which they divide, by 30 percent.
"What this [latest research] means is that the natural form of CLA found in dairy foods is active in reducing the incidence of mammary tumors in rats," says Bauman. "This definitively shows the anti-carcinogenic effect of CLA."
The CLA experiments were carried out at Roswell Park on laboratory rats fed either butter enhanced with CLA from milk or with a highly purified chemical form of the fatty acid. The research showed that feeding the natural CLA butter gave results comparable to the pure chemical form of CLA in reducing tumors in pubescent rats treated with a carcinogen.
"CLA is a natural anti-carcinogen in a natural food. While CLA is a fatty acid, this study does not encourage women to eat a high-fat diet," says Ip. "This is another beneficial aspect of dairy foods, and I would encourage women to eat a well-balanced diet."
Three years ago Bauman's laboratory showed that when certain ingredients, such as plant oils and fresh forage, are added to cattle feed, beneficial unsaturated fatty acids are produced in the animal's digestive system. Bacterial fermentation in the rumen (one of the cow's four stomachs), involves a process called biohydrogenation, producing a five-fold increase in levels of CLA in milk.
Bauman's subsequent work established that a range of diets and management practices also enhanced the cow's ability to produce CLA.
"Most dietary substances exhibiting anti-carcinogenic activity are of plant origin and are only present at trace levels," said Bauman when he released the original research. "However, CLA is found almost exclusively in animal products and is among the most potent of all naturally occurring anti-carcinogens."
The latest research, Bauman says, indicates that the potential exists to identify dietary and management conditions that would increase CLA concentrations in dairy products. He notes that science could use its knowledge of the dairy cow's digestive and metabolic system to design ruminant diets and practices that enhance CLA levels in milk.
Such milk could be delivered to a dairy processing plant to make a range of products with increased CLA content, says David Barbano, Cornell professor of food science.
Ip says that human feasibility pilot studies on CLA's effect on human health could begin as early as next year.
The research report, "Conjugated Linoleic Acid-Enriched Butter Fat Alters Mammary Gland Morphogenesis and Reduces Cancer Risk in the Rat," was authored by Bauman; Ip; Barbano; John McGinley and Henry J. Thompson, both of the AMC Cancer Research Center; and Sebastiano Banni, Elisabetta Angioni and Gianfranca Carta of Cittadella Universitaria.