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 utter 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 last November.
 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, NY, 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 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 fivefold 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. The study was performed by researchers at Cornell;
Roswell Park; AMC Cancer Research Center, Denver; and Cittadella
Universitaria, Cagliari, Italy. 
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