Vitamin B1, molecular model. Vitamin B1 (thiamine) is an essential nutrient that humans are unable to produce and need to obtain from their diet. It is found in flour, beans, pork, and salmon. Vitamin B1 is important for the normal function of the heart, muscles and nervous system, as well as normal growth and development. Deficiency can lead to the disease beriberi, which causes weight loss, emotional disturbances, and limb pain and weakness. Vitamin B1's chemical formula is C12H17N4OS.Atoms are represented as spheres and are colour-coded: carbon (C, grey), hydrogen (H, turquoise), nitrogen (N, blue), oxygen (O, red) and sulphur (S, yellow).