Evidence keeps accumulating for certain ingredients. In at least one case, exact amounts are recommended.
March 2018 - No dog treat or dietary supplement is allowed to say it actually treats or cures arthritis. That would be a health claim and a flagrant violation of Food and Drug Administration regulations forbidding health claims on products that havent been proven with clear-cut scientific evidence, meaning research and clinical trials conducted according to strict protocols. Health claims are generally reserved for drugs, not foods or supplements you can get without a prescription.