"For the Lord thy God bringeth thee into a good land, a land of brooks of water, of fountains and depths that spring out of valleys and hills; A land of wheat, and barley, and vines, and fig trees, and pomegranates; a land of oil olive, and honey" (Deut. 8:7-8)
Barley was part of a staple diet..but more popular as a 'barley loaf' which we read that Christ fed 5000.
I don't doubt John at all about the benefits of such, but careful about these health food zealots who replace food with tablets and make a profit e.g. Tablets
Often like the vitamins con which makes some folks 'mega-rich'!