I see that your comment was posted quite some time ago, but I still had to respond.
I had the exact same response to wheatgrass. I would drink some in the morning and approximately 45 minutes later I had to take a nap. I tried to work through it, but it made me exhausted.
Not wanting to give up, I continued to drink it. I mixed it with other vegetables when I juiced in an attempt to diminish its affect. Well, after some time, Iíd say a month or so, I tried drinking it straight again. I took 1 ounce. I waited for the same tiredness to affect me but it didnít. Quite the contrary, I became energetic.
Iím now up to 2 ounces a day. My energy level has improved. Another thing that I have noticed, and Iím not sure whether it is a result of the wheatgrass, or from my improved dietary habits, but my arthritic toe (the one that the podiatrist said that only surgery will cure) has not been hurting anymore. Iím so pleased that I can now resume my walking and running exercises. Itís been about 2 years since Iíve been able to walk for longer than 10 minutes without having to stop because of the arthritic pain. Additionally, my blood pressure which was borderline hypertensive is now well within normal ranges.
Again, Iím not sure whether or not the wheatgrass is solely responsible for my improvement in health, but Iím sure it was a contributing factor.