This fat may fight cancer several ways.

A provocative new animal study suggests that early consumption of a fat contained in many animal products may offer some protection against breast cancer. Related research indicates that high amounts of this fat may also help fight a wasting disease that compromises the survival of many sick individuals, including cancer patients.

Known as conjugated linoleic acid (CLA), this unusual fat is a structurally altered form of the essential polyunsaturated fat, linoleic acid. In the March 1 CANCER RESEARCH, biochemist Clement Ip of the Roswell Park Cancer Institute in Buffalo, N.Y, and his colleagues report that diets enriched with CLA reduced a female rat's susceptibility to two breast carcinogens.

In one case, CLA administered just during the 5 weeks when a rat's mammary tissue was maturing offered strong protection against the development of tumors later, when the researchers exposed the animal to one of two potent chemical carcinogens. Animals whose diets contained 1 percent CLA by weight -- the equivalent of about 30 times the amount eaten by the average 155-pound human -- developed just two-thirds as many mammary cancers as rats given no CLA.

In another experiment, the diets of nearly mature females were spiked with 0.5 to 0.05 percent CLA for 38 weeks, beginning just 2 weeks before a single dose of a chemical carcinogen. Though animals in the group receiving the highest dose developed less than half as many mammary tumors as untreated rats, even those receiving the least CLA showed evidence of protection: They developed just 78 percent as many cancers as untreated animals.

Concludes Ip's team, "CLA is by far the most powerful naturally occurring fatty acid known to modulate [tumor formation]."

"What makes this really amazing is that [the lowest active dose] is within the range of what people can eat," says Michael W. Pariza, director of food microbiology and toxicology at the University of Wisconsin-Madison.

First isolated 10 years ago from hamburger, CLA now appears "to be present in any warm-blooded animal," notes Pariza, one of CLA's discoverers. Studies he has headed indicate that the highest concentrations of CLA occur in red meats, turkey, milk, and cheese (SN: 2/11/89, p. 87).

But before people use the new findings to sanction pigging out on bacon, heavy cream, and high-fat cheeses, Ip urges caution. CLA keeps company with some unhealthful companions. Not only do animal products tend to carry high proportions of saturated fats and cholesterol -- risk factors for heart disease -- but they also contain CLA's parent, linoleic acid. Excessive quantities of linoleic acid have been associated with fostering cancer development.

If CLA continues to prove promising, Ip suspects manufacturers will respond by chemically or microbially treating foods to convert more of their ordinary linoleic acid into CLA.

Research by Pariza's team now suggests that CLA may also prove beneficial in treating cachexia, a wasting that occurs when the body catabolizes -- burns up -- muscle in an attempt to meet the high energy demands of fighting certain chronic diseases, such as malaria or cancer.

The Madison-based researchers fed some mice and chickens normal diets; others got diets supplemented with 0.5 percent of either fish oil or CLA. After a week or two, all animals received an injection of a bacterial poison that induces temporary cachexia. Untreated animals and those supplemented with fish oil suffered twice the weight loss of animals supplemented with CLA, Pariza and his coworkers report in the Feb. 28 BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS.

Even more important, Pariza points out, in contrast to several other promising treatments being considered for cachexia, "CLA reversed the catabolic effects without suppressing the immune system." Indeed, he says, these new data suggest "that CLA really is a growth factor -- a nutrient that hasn't been previously identified." He now suspects that CLA achieves its many beneficial effects through some common pathway involving hormonelike substances in the body known as prostaglandins.