Remember the bread we buy in stores is made from refined flour, even the so-called "whole wheat" breads.

If you look at wheat berries themselves, they can be stored for years with no refrigeration needed and are very nutritious. When you grind those wheat berries into flour, you're getting the wheat germ and the fiber and all of the actual nutrients.

Corporations strip these nutrients out, and even go as far as bleaching even more of the protein out for flour used in things like cakes and cookies. This is why you can buy "unbleached all-purpose" white flour, and why it's labeled as "unbleached." Meanwhile, the manufacturers sell the bleached flour under the name "cake flour" as opposed to "bleached flour."

Here's the description from Bod's Red Mill for their cake flour-

Cake flour is a light, finely milled flour with a lower protein content than all-purpose flour. Cake flour is milled from soft wheat and contains the lowest amount of protein when compared to other flours, around 5 to 8%. For comparison’s sake, all purpose flour is usually 10 to 13% protein, which can produce good results for almost any recipe. However, the low protein and high starch content in cake flour helps create the lightest, most delicious cakes possible!

https://www.bobsredmill.com/blog/baking-101/what-is-cake-flour/

You can watch this YouTube video for more information on wheat berries-

https://youtu.be/QrccrOAaHms