The author concludes that eating fish can lower one’s cholesterol. This is based on a study comparing a group that ate fish and a group that didn’t eat fish. The fish-eating group ended up with lower cholesterol levels than the other group, even though the two groups started off with similar cholesterol levels.

The referenced text is part of the support for the author’s conclusion. It helps to eliminate the possibility that the fish-group’s lower cholesterol is just a function of that group starting with lower cholesterol.