White bread is a processed food. That's why white bread is white. Originally, the flour is whole wheat flour, which is darker in color. Then the wheat germ and bran is removed from the wheat by a process called “milling”.
This is done because removing the bran, which contains oil, gives the flour a longer shelf life. A longer shelf life makes it cheaper to sell the product because spoilage is reduced or eliminated.
Processed foods are more profitable than unprocessed foods.
Additionally, the flour is often bleached to remove a slight yellow color and make its baking properties more predictable. The chemicals used to bleach the flour are not edible.
As mentioned above, the benefit of milling is to increase the shelf life of the bread. The down side is that processing foods also removes nutrients, like some dietary fiber, iron, B vitamins and micronutrients.
Remember, the production and sale of processed foods is a business. Food is grown and sold first, to be profitable, then maybe, to be healthy. A significant difference.
The Miami Herald Sun wrote on June 24, 2011, that “The New England Journal of Medicine published research that advised weight-watchers to cut out sugar-sweetened drinks, potatoes and refined grain foods such as white bread, white rice and low-fiber cereals. They urged people to eat more “natural” foods, such as fruit and vegetables, whole grains, nuts and yoghurt, while avoiding anything processed.”
On June 19, 1999, the Center for Science in the Public Interest petitioned the Food and Drug Administration (the FDA) to prohibit the use of potassium bromate, which is used to strengthen bread dough. They charged that the FDA has known for years that bromate causes cancers in laboratory animals, but has failed to ban it.
For your interest’s sake, you might find interesting reading in the FDA’s Defect Levels Handbook. In this government publication you will find what the US Government considers to acceptable levels of contamination in your food. After all, you don’t mind just a little bit of rat hairs or feces in your spaghetti sauce, do you?