Dietary Fat and Risk for Gallstone Disease in Men

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The summary below is from the full report titled "The Effect of Long-Term Intake of cis Unsaturated Fats on the Risk for Gallstone Disease in Men. A Prospective Cohort Study." It is in the 5 October 2004 issue of Annals of Internal Medicine (volume 141, pages 514-522). The authors are C.-J. Tsai, M.F. Leitzmann, W.C. Willett, and E.L. Giovannucci.

What is the problem and what is known about it so far?

Bile is a fluid produced by the liver to help digest food. It is a mixture of cholesterol, fats, and other substances. Changes in bile, such as too much cholesterol, can cause bile to crystallize and form gallstones. Some research suggests that types of fat in the diet may affect a person's chance of developing gallstones. For example, diets high in saturated fat may promote gallstone formation, whereas diets high in unsaturated and monounsaturated fats, which together are called cis unsaturated fats, may make gallstones less likely.

Why did the researchers do this particular study?

To determine whether high levels of cis unsaturated fat in the diet protect a person from developing gallstones.

Who was studied?

45 756 men in the United States between the ages of 40 and 75 years. All were health professionals who had never had gallstones or gallbladder disease when the study started.

How was the study done?

Study participants completed a questionnaire at the start of the study and every 2 years for up to 14 years. They provided information on all aspects of their health, including what they ate and whether they developed gallstones or had to have their gallbladder removed. The researchers compared the number of cases of gallstones in men whose diet had the highest amounts of cis unsaturated fat with those in men whose diet contained the least amount.

What did the researchers find?

Men who ate the most cis unsaturated fat were 18% less likely to develop gallstones compared with men who ate the least. This protective effective was strongest for men who were heavier and less physically active.

What are the limitations of the study?

The study looked only at gallstones that caused symptoms. Because most gallstones cause no symptoms, the findings might not apply to most people. It is also possible that unmeasured dietary or other factors were responsible for the benefit.

What are the implications of the study?

A balanced diet high in cis unsaturated fats may reduce men's risk for developing gallstones.