Here is a brief information about vitamin b complex. Ingredients and sources, combined from wikipedia and answer.com
B complex is a group of water-soluble vitamins including thiamine, riboflavin, niacin, pantothenic acid, biotin, pyridoxine, folic acid, inositol, and vitamin B12 and occurring chiefly in yeast, liver, eggs, and some vegetables.
B complex include the following vitamins-
The group of “B” vitamins includes eight different varieties of vitamins and is collectively called as vitamin B complex. The different vitamins of B complex are available individually in many natural foods but very seldom available in a single source. The human body needs all the eight vitamins on a daily basis and it becomes improbable for us to include so many different varieties of foods in our daily diets. A typically balanced diet that involves various food items, at different intervals during the course of the day, can supplement this requirement but very few of us have the time or inclination to follow this kind of a diet. So, as a result many of us miss out on the required vitamins due to improper intake
All the vitamins in B complex are water soluble. Human body is made of 80% water and when these vitamins come into contact with water, they dissolve. Dissolved vitamin B complex is easily absorbable but human body is designed absorb only the required amounts of nutrients and will either expel the excess quantities or store them for later use. Vitamins in their dissolved state cannot be stored and as a result, are expelled via urine. This means that we will need to replenish all the vitamins of B complex on a daily basis or otherwise suffer health complications.