I have used it while eating meat although it's not as good - it still works - in fact the taste of the urine after you eat meat can really tell you which one is really not agreeing with you. I am a type O blood type however so most meat agrees with my blood and urine comes from the blood. Check the guides tho - they do say meat is bad. I think that's why the fasts are so good. There's no extra load on the body.