B-complex vitamins are essential to mental and emotional well-being. They cannot be stored in your body, so we depend entirely on our daily diet for an adequate supply. B vitamins levels in the blood are affected by alcohol, refined sugars, nicotine, and caffeine, so it is no surprise that many people may be deficient in these. The first clinical effects of insufficient quantities of vitamin B are mood changes, insomnia, changes in appetite, sugar cravings, and impaired drug metabolism. As a group, the B vitamins play an essential role both in mood and anxiety.