If considering that ones intake is nutricianly complete from whichever sources,than:
Since the protein forms of amino acids found in animals arent different than the amino acids found in plant sources there may be another lack in an individuals system that is being replenished by the meat eating. Methylsulfonalmethane, msm,nutricinal sulfer may be responsible here, since it is found in high concentrations in meat. A study of its importance in the cells health and its placement in western scientific understanding is an interesting study.
As a side issue:
Another thing is that we often come under the persuasion that UT is a cure all ,due to an individuals remarkable recovery of health after having tried many other avenues, rather than its being an optimizer.Many of us on the UT continuim attest to its being a super optimizer but still just that. As an optimizer it can only help to the degree that ones system is not lacking something of importance since ut is really only readministering the fluid nutrients and cleaned up water already in the bloodstream. ( not to start the topic of what is really energising the micro built macro system we call organic life, because there are numerous examples of superior health while individuals are eating little or nothing)