B vitamins are water-soluble vitamins that are not stored well in the body. They must be continuously replenished either through diet or supplements. Because the typical American diet consists of heavily processed foods that are nutritionally depleted, many people are not getting the right amount of B vitamins. These can be helpful for those who are stressed out and feel weak or fatigued, and are also required to keep the skin, hair, and nails healthy. B vitamins are also vital for cardiovascular health.