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Vitamin B-12 deficiency and irritable bowel syndrome (IBS) symptoms are similar.  If a person is having symptoms of IBS, it is a good idea to have diagnostic tests that will rule out vitamin B-12 deficiency.  Examples of symptoms experienced in both IBS and Vitamin B-12 deficiency are: frequent and uncontrollable diarrhea, stomach cramping and pain.

A lack of sufficient vitamin B-12 affects the digestive system because the vitamin is essential in the metabolism of carbohydrates, fats, and proteins.  It is a reasonable assumption that people with severe symptoms of IBS may develop a vitamin B-12 deficiency due to problems with food intake, digestion, and absorption.  Chronic IBS-related diarrhea may also lead to an increased loss of B-12.