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Fatty Acid in Milk May Ward Off Breast Cancer

In rodents, linoleic acid halts formation of vessels tumors need

FRIDAY, Sept. 27, 2002 (HealthDayNews) -- A fatty acid in milk and meat appears to muzzle budding breast cancer by shutting off its ability to summon blood vessels, a new study shows.

The substance, conjugated linoleic acid (CLA), clamps down on the formation of new blood vessels -- a process called angiogenesis -- that tumors need to support their lust for nutrients.

"It appears to be an anti-angiogenic compound and a nontoxic one," said Margot Ip of the Roswell Park Cancer Institute in Buffalo, N.Y., who led the work. Ip presented her findings today at a meeting in Orlando of the U.S. Department of Defense Breast Cancer Research Program.

Ip's group first dosed rat mammary cells in a dish with CLA, and saw that in the presence of the chemical they produced far fewer tiny blood vessels. They then fed the substance to live rats, and saw in tissue samples that the growth of new vessels was cut by up to 80 percent.

Ip said CLA seems to prevent one class of flexible mammary cells, called stromal cells, from becoming vessels that can feed tumors that form in the milk ducts. Instead, it encourages these cells to convert into harmless fatty tissue.

CLA has anti-cancer properties in a wide range of cells, from the breast to the colon. But its effects are overwhelmed by the harmful impact of other fats that are more prevalent in food, said Jack Vanden Heuvel, a molecular toxicologist at Penn State University who studies the chemical.

"CLA is just one type of fatty acid that's in all those foods that are high in fats, and on balance they're bad," Vanden Heuvel said. Scientists are trying to increase the concentration of CLA in dairy products by manipulating what cows eat.

The substance is also available as a dietary supplement, and evidence suggests that it can lower body fat while increasing lean muscle mass. However, it hasn't been around as a diet aid long enough to know if it indeed prevents cancer in people, Vanden Heuvel said.

Vanden Heuvel said the latest study agrees with his own research, which has found that CLA binds to and activates a protein called PPAR-gamma. This protein helps cells become a variety of tissues, whereas tumors are cells that have already committed to a single function and are more prone to cancerous mutations.

His group has found that CLA acts much like a novel class of diabetes drugs called the glitazones, which make fat cells better able to handle blood sugar. Research suggests that these medications not only block angiogenesis but also may prevent colon, breast and prostate tumors.

"There's solid evidence that CLA has the ability to inhibit cancer," said Mark McGuire, a lactation biologist at the University of Idaho in Moscow who studies the chemical. Humans get about 95 percent of their CLA in beef and milk. Yet because it's a fatty acid, people who drink skim milk aren't getting any in their glass.

Rat data and human studies from Finland suggest that bumping up CLA intake by only 20 percent can slice the risk of breast cancer in half, McGuire said. One way to do that is to swap whole milk for skim and to cook with butter instead of vegetable oil or margarine.

Of course, making those changes increases saturated fat consumption, which can hike the risk of heart disease. But McGuire said he and his colleagues have found that women who drink whole milk in moderation don't develop unhealthy blood fat levels that might put them at risk of heart and vessel problems.

In another study presented at today's meeting, Alabama scientist found that when you eat a cancer-preventing food may be as important as simply eating it at all. The researchers showed that rats fed the soy protein genistein, which may prevent breast cancer, had fewer tumors later on if they ate the substance before entering puberty.

The findings suggest that adolescent and pre-adolescent girls who eat a soy-rich diet may ward off breast cancer later in life. That agrees with a 2001 study, which found that Chinese women who ate high-soy foods when they were teenagers had half the incidence of breast cancer as those who ate less of the nutrient.

Coral Lamartiniere, a toxicologist at the University of Alabama, Birmingham, who led the latest work, said genistein helps immature mammary cells become "differentiated"-- that is, it prompts them to choose a specific function in the breast. "It's undifferentiated cells that are susceptible to carcinogens," he said.

What To Do

To find out more about breast cancer, try the Susan G. Komen foundation or MEDLINEplus.

SOURCES: Margot Ip, Ph.D., professor of pharmacology, Roswell Park Cancer Institute, Buffalo; Jack Vanden Heuvel, Ph.D., associate professor of toxicology, department of veterinary science, Pennsylvania State University, State College; Mark McGuire, Ph.D., associate professor of lactation biology, department of animal and veterinary science, University of Idaho, Moscow; Coral Lamartiniere, Ph.D., professor of pharmacology and toxicology, University of Alabama, Birmingham; Sept. 27, 2002, presentation, U.S. Department of Defense Breast Cancer Research Program, Orlando, Fla.
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