Gas in the intestinal tract is caused when the good bacteria present in the digestive tract become less. This bacteria helps in digestion and also in producing vitamins and increasing immunity. The bacteria produces gas while digesting food and sugars and starch and cellulose that have not been digested while passing from the small intestine. The gas is caused by sugary and sugary fruits. Another factor is the decrease in the consumption of fibre. Carbonated sodas also cause gas.