Has anyone ever tried a wheatgrass supplement?

I just joined a gym and got a free session with a personal trainer. He recommended a ton of different vitamins and supplements, but especially a wheatgrass juice powder: http://www.sweetwheat.com/store/wheatgrass-ju...

The gym sells wheatgrass shots (there's a little store / smoothie counter inside) so I guess it's pretty healthy. Anyone? Thoughts?