People who eat a lot of trans fatty acids increase their risk of heart disease and diabetes, two diseases that might be caused partly by systemic inflammation. A group of Harvard researchers set out to look for any relationship between trans fatty acids and systemic inflammation.

What the researchers wanted to know: What is the relationship between systemic inflamation and eating trans fatty acids?

What they did: The researchers worked with some of the women in the Nurses' Health Study and the Nurses' Health Study II, two long-term studies of women's health. (Nurses were used for the studies because the designers figured healthcare professionals would be more motivated to stick with a long-term health study than other people would.) The women are generally pretty healthy. The researchers in this study used women's questionnaires to find out what foods they ate, then calculated trans fatty acid consumption from that. Blood samples were used to find markers of inflammation: C-reactive protein (CRP) levels, interleukin 6 (IL-6) concentrations, and the levels of two soluble tumor necrosis factor alpha receptors (sTNF-R1 and sTNF-R2). High levels of all of these molecules are related to heart disease.

What they found: Women who ate more trans fatty acids had higher levels of the tumor necrosis factor receptors. There was no such relationship with IL-6 and CRP levels overall, but women with a higher body mass index (BMI) did have higher levels of IL-6 and CRP if they ate more trans fatty acids.

What it means for you: Trans fatty acids may increase systemic inflammation in healthy women. So eating foods with lots of trans fatty acids—such as fast foods, packaged snack foods, and margarine—probably isn't good for you.

Caveats: The researchers didn't actually measure the trans fatty acids the women were taking in; they just estimated trans fatty acids based on what women said they eat. But the amount of trans fatty acids in a food varies depending on how it was made.

Find out more: For information on trans fatty acids, go the U.S. Food and Drug Administration's website: http://www.fda.gov

Confused by "good fat" and "bad fat"? The American Diabetes Assocation breaks it down: http://www.diabetes.org

Read the article: Mozaffarian, D., et al. "Dietary Intake of Trans Fatty Acids and Systemic Inflammation in Women." American Journal of Clinical Nutrition. April 2004, Vol. 79, pp. 606-612.

The abstract at National Library of Medicine: http://www.ncbi.nlm.nih.gov