809 members of the Old Order Amish community agreed to go to a clinic in Lancaster in order to drink a rich milkshake made mostly of heavy cream. Of course, that's not the only thing they've done. Researchers then took samples of their blood, determining how much fat was churning through their bloodstreams. Most of study participants had their levels of triglycerides rose steadily for three to four hours and then declined. Triglycerides is a common form of fat in the blood. Amazing as it seems, 5 percent of them had an extraordinary reaction: their triglyceride levels started out low and hardly budged.

It seems that the individuals who barely responded have a mutation that disables one of their two copies of a gene called apoC-III. The gene codes a protein, APOC3, which normally slows the breakdown of triglycerides. Of course, with this mutation, people break down triglycerides very quickly. Furthermore, the test subjects also had low levels of LDL cholesterol, which at high levels increases heart disease risk. They also have high levels of HDL cholesterol, which decreases the risk of heart disease and they appear to have arteries relatively clear of plaque.

In order to find the gene mutation, researchers led by Toni Pollin, an assistant professor of medicine at the University of Maryland School of Medicine scanned the entire genomes of their study subjects, looking for genetic regions that were linked to levels of blood triglycerides. They ultimately got to a region that contained the apoC-III gene. After sequencing it, they found that the mutation destroyed its function. Scientists suspected that apoC-III might have such a role, but it's now clear for all of them.