Vitamin B is important for metabolism, immune health, energy & the nervous system. That last part is particularly important. Your digestive system has a vast nerve network called the Enteric Nervous System. Nervous system dysfunction is one theory behind the cause of IBS. It is very important someone dealing with IBS is getting enough Vitamin B.
Vitamin B is actually a classification of many different vitamins ranging from Vitamin B1 to Vitamin B9, as well as Vitamin B12. Most people will want a Vitamin B Complex which includes all the B-Vitamins. I personally use Nature’s Bounty Vitamin B Complex With Vitamin C.
Vitamin B12 is particularly important for nerve health. There are two main types on the market: Cyanocobalamin and Methylcobalamin. The methyl version is more easily absorbed by the body, while Cyanocobalamin has to be converted to it’s methyl form first. The body does not do a good job absorbing B12 through the digestive tract. That is why B12 usually comes in sublingual tablets that you dissolve under your tongue. The tongue has pathways to the bloodstream with are more direct & large enough to pass the B12 molecules through. A lot of these products have sugar substitutes in them like mannitol or sorbitol, so beware because these can cause digestive upset for some. You may want to have your vitamin B12 levels tested by your doctor. If they are low then then you might need to look into B12 injections or a prescription nasal spray.