Vitamin B is a complex of several vitamins. The name arises because it was once considered a single vitamin, much like Vitamin C or Vitamin D. Since later research has shown it is in fact a complex of chemically distinct vitamins that happen to often coexist in the same foods, the name has gradually declined in use, being replaced by the generic term "the B vitamins", the vitamin B complex, or by the specific names of each vitamin.

The B vitamins are:

• Vitamin B-1 (Thiamine)
• Vitamin B-2, also Vitamin G (Riboflavin)
• Vitamin B-3, also Vitamin P or Vitamin PP (Niacin)
• Vitamin B-5 (Pantothenic acid)
• Vitamin B-6 (Pyridoxine and Pyridoxamine)
• Vitamin B-7, also Vitamin H (Biotin)
• Vitamin B-9, also Vitamin M (Folic acid)
• Vitamin B-12 (Cyanocobalamin)

Several other substances which are not human vitamins have been referred to as B vitamins. These include:

• Vitamin B-4 (Adenine)
• Vitamin B-7* — more commonly called Vitamin I
• Vitamin B-8 (Ergadenylic acid)
• Vitamin B-10, also Vitamin R (Pteroylmonoglutamic acid mixed with other B vitamins)
• Vitamin B-11, also Vitamin S
• Vitamin B-13 (Pyrimidinecarboxylic acid or orotic acid, often misspelled erotic acid)
• Vitamin B-14 — a mixture of B-10 and B-11
• Vitamin B-15 (Pangamic acid )
• Vitamin B-16
• Vitamin B-17 (Amygdalin)
• Vitamin B-22, often claimed as an ingredient of Aloe vera extracts
• Vitamin B-c, another name for Vitamin B-9 (Folic acid)
• Vitamin B-h (Inositol)
• Vitamin B-t (L-Carnitine)
• Vitamin B-w, another name for Vitamin B-7 (Biotin)
• Vitamin B-x, also PABA (Para-Aminobenzoic acid)

In addition to coexisting in the same foods, the B vitamins often work together to bolster metabolism, maintain healthy skin and muscle tone, enhance immune and nervous system function, and promote cell growth and division — including that of the red blood cells that help prevent anemia.

Together they also help combat the symptoms and causes of stress, depression, and cardiovascular disease.

All B vitamins are water soluble, and are dispersed throughout the body and must be replenished daily with any excess excreted in the urine.

Brewer's yeast is a good source of Vitamin B.

Source material

Linda Clark's "Know your Nutrition": ISBN 0879834013