B vitamins work together and are commonly called B-Complex. The
symptoms of deficiency include inflamed skin, digestive
problems, and mental impairment. B vitamins are essential for
converting the food you eat into usable energy. Deficiencies
used to be rare, seen mostly in vegetarians who don’t enough of
the foods containing B vitamins, and alcoholics who have
depleted their vitamin B reserves. Now, as more people are
converting to vegetarian diets, deficiency is increasing. The
combination of iron, b vitamins, and zinc is a powerful stress
fighter. Folic acid, or B9 with B12 have recently been tied to
preventing and even possibly reversing macular degeneration and
Alzheimer's. B vitamins are water soluble, so your body discards
what it doesn't need. B complex is sort of, well... complex.
You'll find the details of each B Vitamin in the Vitamin
listings-