In a type of lab mouse with high cholesterol, eating fats like olive oil doesn’t help reduce artery damage any more than eating fats like butter — both lead to about the same amount of fatty buildup in the arteries after 16 weeks.

In a type of lab mouse that’s prone to heart disease, eating healthy fats like those in fish or vegetable oils led to less buildup in the arteries after 16 weeks compared to eating saturated fats like butter or lard.

In mice genetically prone to heart disease, eating certain fats like those in margarine or some oils led to more artery gunk after 16 weeks compared to other fats found in fish or nuts.

When mice with a genetic predisposition to clogged arteries ate a diet with olive oil and nuts instead of butter and animal fat, their artery plaques got smaller.

Dietary intake of saturated fatty acids increases circulating levels of low-density lipoprotein (LDL) cholesterol in humans through upregulation of hepatic cholesterol synthesis and reduced LDL receptor expression.

Mice that ate olive oil and nuts instead of butter had less cholesterol and fat in their blood, which might help keep their arteries from getting clogged.