Vitamin U, molecular model. The chemical formula for vitamin U, also called S-methylmethionine, is C6.H15.N.O2.S. Atoms are represented as spheres and are colour-coded: carbon (blue), hydrogen (gold), nitrogen (dark blue), oxygen (red) and sulphur (yellow). Vitamin U is not officially recognised as a true vitamin, since it is a derivative of the amino acid (protein component) methionine. Vitamin U is found in a wide variety of fruit, vegetables and legumes. It is believed to have beneficial effects on the function of the digestive system. However, there is currently little research conclusively demonstrating the benefits or deficiency effects of vitamin U (as of 2008).