Methionine In Feline Diets
The basic 30-year formula of Uretic™ fed to tens of thousands of cats through multiple generations has not changed. Nutraceuticals have been incorporated for their health benefits and these can only help urinary problems, not encourage them. See: http://www.wysong.net/dietfeatures.php.
The new Uretic™ (there is actually no "new" Uretic™ since the formulas are constantly being upgraded as science advances), just like the old Uretic™, is high in protein. A higher protein diet also helps to promote a more acidic urine pH which discourages struvite formation. But urinary stones in cats is a multifactorial problem and cannot be reduced to the inclusion or exclusion of just one particular ingredient. See: http://www.wysong.net/pet-health-and-nutrition/rationale-for-feline-diets.php.
The rumor that the new formulas may cause stones began with those who objected to the removal of synthetic methionine from the formula, not because the diets caused stone formation. This formula change was done due to the potential toxicity of methionine as a synthetic isolate. What critics have not recognized is that the formulas have been enhanced with natural methionine as found in sesame seeds. See: http://www.wysong.net/pet-health-and-nutrition/methionine.php.
L-Methionine in sesame, as opposed to the synthetic DL-methionine, naturally helps acidify urine. A more acidic urine pH (lower pH), is helpful in preventing urinary tract infections and struvite crystals.
Results of Uretic™ use can be found here: http://www.wysong.net/testimonials.php