Good Trans Fat Found
Initially discovered as an anticarcinogen in ground beef patties in 1987, CLA has become an exciting new area for nutrition research.
"CLA is created naturally in the gut of ruminant animals, such as cattle and sheep," explains Catherine Field, Ph.D., Professor of Nutrition at the University of Alberta. "During digestion, microorganisms convert linoleic acid, a common fatty acid in the diet of these animals, into CLA. This beneficial trans fat is structurally very different from the trans fats that are made during the hydrogenation of vegetable oils."
It has been known for a long time that humans don't metabolize CLA the same way they do other trans fats. That's why Health Canada does not require food companies to include CLA when listing the trans fat in the Nutrition Facts table.
Field, who has been doing laboratory studies on CLA for over five years, says that at the present time, the most convincing evidence for the benefit of CLA is in cancer models. "CLA is very potent at reducing the rate at which breast and cancer cells grow in animals. It also suppresses the growth of human cancer cells grown in the laboratory, including breast, skin and prostate cancer cells."
While it would be ideal to conduct human trials to verify these findings, Field explains that there would be ethical issues in withholding conventional treatment from people who have cancer. "At this time we don't know exactly how CLA prevents tumor growth," says Field. "However, the animal models suggest that including CLA-rich foods in the diet from the time mammary glands begin to develop in the teenage years may make women more resistant to breast tumors later in life."
Along with the cancer research there is rapidly accumulating evidence from well-established animal models of CLA's potential benefits in diabetes, obesity, immune function and musculoskeletal development. This has motivated food scientists to look for ways to naturally increase the CLA content of foods.
"Beef can provide high amounts of CLA per serving," says Priya Mir, Ph.D., a Ruminant Nutritionist with Agriculture and Agri-Food Canada in Lethbridge, Alberta, "Dairy foods can be another good source."
Mir's research shows that by altering the diet of beef cattle the CLA content of beef can be significantly increased. "Sunflower seeds have the right fatty acid, and grass or hay and grains, such as barley, provide energy and fibre. With all these dietary components present, bacteria normally present in the cow's gut convert more linoleic acid to CLA," says Mir. She has also found that adding silage to the diet of beef cattle prevents this conversion from happening.
The new information about CLA is changing the way dietitians, such as Field, counsel consumers. "Over the past 20 years people have developed a fat phobia," says Field. "Many are cutting back on the wrong foods. To help reduce calorie intake, Canadians should cut calories from extra foods, such as French fries, chips and other fatty snack foods and soft drinks. However, they should not be avoiding all fats. Foods, such as meat and dairy products, contain beneficial fats, such as CLA."
As well, Field reminds consumers that meat has other essential nutrients - such as iron, zinc, vitamin B12 and complete protein. "It's difficult for Canadians to get adequate amounts of these nutrients in a diet that doesn't contain meat," says Field.
The research on CLA is still growing. More science is needed to define how much CLA we need for health benefits and exactly how it works in the human body.
TIPS TO BOOST YOUR CLA INTAKE
- Add ground beef to pasta sauces and chili
- Top salads with cheese or cooked beef strips
- Add milk to soups
- Snack on yogurt and cheese
- Fix a quick stir-fry of beef and vegetables
