Assurance of "double blind" design: In order that the investigators will not know to which group the subject belongs, the code of the randomization will be saved in the computer in a protected by user name and the password will be know only to Research Assistant 2 (responsible for randomization, who will be the only one who knows in which box, No. 1 or No. 2, has the active ingredient, Vit. B12. The code which were assigned to the boxes for the investigators will be revealed only after the data has been processed. The research assistants will not take part in data processing.