Oil is not an essential ingredient in bread.
It is common, around the world, to use animal fat in different styles of bread made with refined white flour. I do not use any animal fat in my bread. Animal fat is harmful to health. Those types of bread, made with pure white flour and animal fat are not a good food. Their effect is the deposition of cholesterol and triglycerides in the inner walls of arteries, thereby narrowing and hardening them (Arteriosclerosis) which raises blood pressure and predisposes to serious heart problems.
Use olive oil, grapeseed oil or another edible one. You can also use a good no trans fat margarine but never use animal fat.
Why use oil? Oil is not a basic ingredient of bread. Discretion should be used when adding oil in bread. The original French bread and many traditional bread types in France and Italy do not carry grease or oil in the dough. Among the Italians, from whom I descend from my father’s line it is usual to eat a piece of bread, fresh or toasted, dipped in a little olive oil with a few grains of fine salt. Despite its extreme simplicity, this combination results in a delicacy.
I always use a little oil when making whole wheat bread. Lack of oil results in a rough and hard crust and a harsh dry crumb. Without oil whole wheat bread dries quickly. Therefore I use generally ¼ cup grapeseed oil per kilogram of flour.
In bakeries around us, it is common the addition of only 2% oil or animal fat in the regular white bread.
Do not use oil in rye bread because the taste of the resulting bread is not the best. In general and in different countries, rye bread is made without oil.
Hydrogenated vegetable oil present in some vegetable kinds of margarine is harmful to health because of its content of “trans” fats. Hydrogenation of the lighter oils to convert them in margarine produces fats that do not exist in nature and the human body does not have the ability to digest, so they accumulate in the body and produce serious disorders over time.