Vitamin B12, also known as cobalamin, is a B vitamin essential for energy production, particularly in the skeletal muscles. Individuals who lack vitamin B in adequate amounts will often experience fatigue and muscle weakness. Most deficiencies are due to lack of red meat in the diet, as this is the best source of B12 or a genetic mutation which results in the inability to produce a protein called Intrinsic Factor, which in necessary to convert B12 into its active form.
As previously noted, the best source for vitamin B12 is red meat, this is perfectly fine in moderation but red meat has been linked to an increase in medical conditions such as colon and/or rectal cancer and can also cause intestinal discomfort if it is eaten in large quantities. Some of these negative side effects are due to the presence of nitrates, which act as a preservative and coloring agent in red meat.
If you are a serious body builder, a lack of B12 will be deleterious to your muscle development and growth and will leave you feeling rather fatigued after a training session. This problem is well known, which is why vitamin B12 is often available in large quantities in many pre-workout formulas. This is an efficient way to obtain the necessary vitamin B12 stores for energy and muscle development, while avoiding the harmful effects of traditional sources.
If an individual must increase their vitamin B12 intake, a pre-workout may be one of the better ways to do this.