Conjugating Fatty Acids, Not Verbs
From beating breast cancer to eradicating those extra pounds of pudge, can conjugated linoleic do everything it’s touted to do?
by Shannon Linderoth and Clint Peck

Think back to basic chemistry for a minute -- atoms, molecules, compounds, the basic stuff of which we are all made. Pretty interesting, maybe even mind-boggling if you ponder how the combination thereof forms everything in and around us. 

And there’s one compound in particular that has lit a fire under scientists and consumers recently, a development that may have far-reaching, positive effects on milk and meat consumption. 

Conjugated linoleic acid (CLA), reputed to lower cancer risk and trigger weight loss, is the current star of the research community and is bandied about by nutrition buffs. The big bonus for dairy and beef producers is that CLA is a naturally occurring fatty acid found in significant amounts only in foods produced from ruminants. 

“It’s an exploding area,” says Doug DiRienzo, director of nutrition research for Dairy Management Inc., which funds portions of current CLA research. “Many advances have occurred in CLA research recently, making the compound made up of a lot of different isomers more understandable. The biggest changes have come in about the last four months.  We’re now seeing a significant divergence in the direction CLA research is taking, as it’s becoming apparent that a specific health benefit may depend on which isomer of CLA is consumed.”

Since CLA was first isolated and identified more than a decade ago by Michael Pariza, director of the University of Wisconsin-Madison’s Food Research Institute, the list of research projects and CLA-related health benefits continues to grow almost exponentially. Pariza, a food scientist, isolated CLA while looking for something in cooked hamburger that prevented skin cancer in mice. 

Research to date has focused primarily on laboratory animals, linking CLA to a number of anti-carcinogenic, anti-diabetic and anti-atherogenic properties. 

The studies have also been done exclusively with synthetic forms of CLA, but that’s changing rapidly. “We saw all kinds of wonderful results with the synthetic CLA, so the question now becomes, ‘can we replicate the same effects with natural forms of CLA?’” asks DiRienzo.  “The cis-9, trans-11 isomer (see the near-by sidebar) is the form commonly found in ruminant animals, and is the isomer most effective in lowering cancer risks.” 

Simply speaking, CLA is produced in the rumen when certain rumen bacteria change the structure (conjugation) of free linoleic acid contained in feeds and forages. 

Foods from ruminant sources generally have CLA levels ranging from 3 to 7 milligrams per gram of fat. While the effective “dose” levels of CLA in human diets are still being investigated, fish, pork and seafood are not significant sources of CLA.  Fruits, vegetables and other foods, excluding vegetable oils, contain little or no CLA.

Mark McGuire, a researcher in the Department of Animal and Veterinary Science at the University of Idaho, Moscow, says research using laboratory animals and cell culture systems consistently shows even relatively low dietary levels of CLA found in beef and milk can help reduce the risk of cancer.

The same holds for diets including higher levels of CLA. Research at Roswell Park Cancer Institute indicates feeding butter with high levels of CLA produced from high, natural-CLA milk was as effective in fighting breast cancer as its synthetic counterparts.

“Tissue analysis showed higher levels of CLA in animals that consume the high-CLA butter,” DiRienzo recounts. “We’re exploring why this happens. Does it mean naturally produced CLA is more easily taken up of is something else going on? As research proceeds, it’s going to be critical to understand which CLA isomer is being used.”

“Clearly, further work, especially using human subjects, will be required to characterize the potential benefits of natural CLA consumption on human health,” says McGuire. He and wife, Shelley, a human nutritionist at nearby Washington State University, suggest the designation of foods containing high amounts of natural CLA be considered as meeting the definitions of “functional foods.”

The effects of CLA on carcinogens are dramatic, but little information is available on how CLA prevents or inhibits cancer. It’s generally believed CLA acts by signaling the immune system and regulating the metabolism by inhibiting cellular enzymes that take up fat. 

“All cellular membranes are made from fat and fatty acids and are involved in cellular ‘signaling’,” explains Mark Cook, an animal scientist at UW Madison who has worked closely with Pariza. “Fat is an important constituent of life.”

But, “This does not mean we should increase our total fat intake,” says Cook. “It simply means we should be investigating which fatty acids are harmful and which are beneficial.”

For example, linoleic acid is beneficial in limited amounts and is essential to growth, according to Pariza. However, excess linoleic acid can enhance malignant tumor growth. 

Interesting, according to Shelley McGuire, recent evidence shows no rise of coronary heart disease with greater butter consumption, while intake of margarine -- a food lacking CLA -- actually has been associated with increased risk of heart disease. 

She notes that if butter were substituted for margarine in the current American diet, rumenic acid (CLA) intake would increase approximately 54 milligrams per day. “This would result in an intake amazingly close to the amount of CLA consumed by Finnish women, who have the lowest risk of breast cancer.”  She adds that eating beef instead of chicken would also dramatically increase CLA intake. 

A ruminant’s diet can influence the levels of CLA deposited in fat tissues and milk. In research at the U.S. Dairy Forage Center in Madison, WI, CLA levels were highest -- nearly four times higher -- in milk from dairy cows grazing pasture grasses and from cows that had soybean oil added to their conventional diets. 

“However, we’re still a long step away from making feeding recommendations to producers,” notes DiRienzo. 

“The market for high CLA dairy products isn’t there yet,” notes David Pelzer, senior director of industry relations for DMI. “It’s not yet going to financially reward farmers.”

But, optimism remains high that sometime in the future, that fact could change. “We’re doing the research to create high CLA milk that we can turn into product,” says DiRienzo. “So should it become a market, U.S. dairy producers will be poised to have a competitive edge.” 

Factors that alter rumen fermentation and rumen microbial population are keys to controlling CLA synthesis, according to Mark McGuire. He and other researchers are looking at everything from fiber to ionophores as feed ingredients that might improve the synthesis and deposition of CLA in milk.

But Shelly McGuire suggests it may not be necessary to alter the CLA content of beef and dairy products to benefit human health. “It may be more reasonable that we focus simply on increasing our basal intakes of dairy and beef products.”

Reprinted with permission from Dairy Producer.

Shannon Linderoth is Editor of Dairy Producer.
Clint Peck is Editor of Western Beef Producer and Montana Farmer-Stockman.