Vitamin B12 or cobalamin is essential for the body as it is involved in several essential metabolic reactions. However, humans cannot synthesize it, which requires an exogenous intake to avoid the undesirable consequences of its deficiency. Various studies have shown that lactic acid bacteria can increase cobalamin levels in food. In this context, this book summarizes the new scientific data on this production of B vitamins by lactic acid bacteria and their modulation in human health.