PERSONAL HEALTH : Downside of Polyunsaturated Fats

Corn oil and other polyunsaturated fats may be good for the heart but, in excess, bad for the immune system.

At the American Dietetic Assn.’s annual meeting in Kansas City, Mo., Monday, Dale Ames Kline, a dietitian on the staff at Oceanside’s Tri-City Medical Center, recommended that people under stress avoid excess polyunsaturated oils. AIDS and arthritis patients, in particular, should watch their intake. But, before the general public takes her advice, she says they should first evaluate their own family history. “If there is a family history of heart disease, for instance, you should be concerned more about that than the immune system,” she says.

Although researchers don’t know exactly how excess polyunsaturated oils may affect the immune system, Kline theorizes that excess fat might turn off the immune system response against “invaders” too early.

How much polyunsaturated fat is too much? In recent animal studies, Kline says that, if 24% to 30% of total calories come from polyunsaturated fats, it compromises the immune system. Current government guidelines suggest that 30% of total calories come from fat of all kinds (up to 10% polyunsaturated, 10% to 15% monounsaturated fats like olive oil and less than 10% saturated fats such as those found in beef). However, Kline points out that Americans typically eat 38% to 40% of their total daily calories from fat.

But Evelyn Tribole, an Irvine dietitian, calls her colleague’s recommendation to avoid polyunsaturated oils premature. “Concentrate on cutting down on total fat (to the recommended maximum),” Tribole advises. “That’s enough. There’s no need to pay special attention to polyunsaturated fats on the basis of preliminary animal studies.”