"Vitamin U", although this is not recognised as a vitamin, rather merely a name. S-Methylmethionine is sometimes called vitamin U in , but it is not recognized as a by mainstream science. Methionine in itself has not been demonstrated as effective for treating and duodenal ulcers. Its proponents claim that sources of methionine are limited, or claim it can be found only in raw ; however, these claims are incorrect. Methionine is a common found in a wide variety of , , and .