Vitamin C is important for overall health & bodily function. Usually it’s well known for boosting your immune system & increasing energy. Vitamin C supplements can however give people stomach issues. The best Vitamin C supplement for someone dealing with IBS is one that contains Sodium Ascorbate instead of Ascorbic Acid. Sodium ascorbate is ascorbic acid that has been buffered with sodium making it easier on the stomach. It is usually available in powdered form making it easy to mix in with food or water. It does have a salty taste though.
There are also some that feel ‘megadosing’ with Vitamin C can cure many different ailments. These claims have not been definitively proven & I would not recommended megadosing for someone dealing with IBS.
I have personally used Source Naturals’ Sodium Ascorbate, but you’re free to use which ever brand you like.