A small group of people carries a gene mutation that protects their hearts against the negative effects of a high-fat diet. The study on 809 people from the Old Order Amish of Lancaster County, Pa. has found that this mutation appears to speed up the breakdown of fats in the blood, which can cause furring of the arteries, a sign of heart disease.

In the study, Toni Pollin PhD, an assistant professor of medicine at the University of Maryland School of Medicine, in Baltimore, and colleagues gave the members of the Old Order Amish community in Lancaster County, Pennsylvania., a super-high-fat milk shake (78 percent of calories from fat), and then monitored them for the next six hours. The researchers used blood samples to measure how much fat was churning through their bloodstreams. Some participants were also tested for the presence of calcium deposits in their coronary arteries, a sign of cardiovascular disease.

The gene in question is called APOC3 and researchers found that 5 percent of the people they studied had the mutation that reduced levels of triglyceride fats in the blood and helped prevent heart disease. The gene produces a protein that inhibits the breakdown of triglycerides, which are fat particles associated with an increased risk of coronary artery disease. Those with APOC-III had the most diminished levels of triglyceride, most probably for the reason that they were able to break down more of the fat in their bloodstream.

“Our findings suggest that having a lifelong deficiency of apoC-III helps to protect people from developing cardiovascular disease,” the researchers concluded. The team selected the Amish for the study because they have a low incidence of heart disease despite of high-fat diets.