OncoLink News In Focus: What's the scoop on trans fat?

Marilynn Larkin, MA

On Friday, November 12, the US Food and Drug Administration (FDA) proposed a change on nutrition labels that would require manufacturers to list the amount of trans fat contained in products such as cookies, crackers, and other processed foods. The proposed change is the first since 1994, when the government initially required that the per serving amount of cholesterol, fat, sodium, and certain nutrients be listed on food labels.

Just what is trans fat (technically, trans fatty acids)? This is the type of fat made when liquid oils are hydrogenated, a process which solidifies them. Hydrogenation increases the shelf life and flavor stability of snacks, stick margarine and shortening, and other products that contain these oils.

But mounting evidence suggests that trans fat also increases blood levels of low density lipoprotein (LDL)-cholesterol, the so-called "bad" cholesterol, which in turn increases the risk of coronary heart disease. And that is at the heart of the FDA proposal. The new label, if approved, would include the amount of trans fat (as well as saturated fat, which is already on the label) in a serving, and would limit the amount of trans fat foods could contain if manufacturers want to make content (eg, "lean" or "low in saturated fat") or health claims. Details are posted on the FDA website.

However, this does not mean all oils--or fats, for that matter--should be routed out of your diet, even if you have cancer or are at risk for a recurrence, says registered dietitian Katrina Claghorn, a nutrition specialist at the University of Pennsylvania's Cancer Center. "We're finding that omega-3 fatty acids -- found in fish, whole grains and flaxseed -- and omega-6 fatty acids, found in polyunsaturated [not hydrogenated] vegetable oils, have benefits in terms of immunity," she notes. But these and other fats should comprise about 30% of your diet at most.

"Contrary to what we used to believe, including a moderate amount of fat in your diet does not contribute to breast cancer, for example. However, being overweight does contribute to breast cancer, and a high-fat diet is more likely to put on pounds." In addition, if you eat too many fatty foods, you probably won't be eating enough plant foods and fiber--and this could also increase your cancer risk.

What does 30% of your diet mean in real terms? Take the number of calories you should normally be consuming--generally, about 1800 daily for women, 2000 for men. One gram of fat is 9 calories, which means that women should be having at most about about 50 grams (450 calories) of fat daily, and men, 60 grams (630 calories), according to Ms. Claghorn. She suggests that patients start by figuring out how much fat they are actually eating daily ("most people are astounded at how much fat they're taking in"); then make appropriate substitutions), while also increasing the amount of fruits, vegetables, and grains on the menu. This kind of diet "is appropriate for all chronic diseases, of which cancer is one," she says.

There is a caveat, however. "We usually say there are two cancer diets: the one you follow when you are going through treatment, and you need to maintain your nutrition status anyway you can--and the healthful diet you should have followed beforehand, which can prevent cancer or prevent a recurrence," notes Ms. Claghorn. "But even if you didn't follow that healthful diet to start with, it's not too late to start now."