Fiber is great for you. It provides support to your body’s natural detoxification system. It makes you feel fuller so you are less likely to overeat. It promotes better heart health. It even helps to keep your cholesterol in check. But there’s one major side effect risk: the gassiness after eating fiber.
What’s the deal with that? To begin, you should know that gassiness after eating fiber doesn’t come from all forms. There are two types of fiber: soluble and insoluble fiber. While they can both cause some degree of gas – as can most foods – it is the soluble form that tends to result in the stinky, uncomfortable and occasionally embarrassing side effects. The reason is that soluble fiber tends to be found in foods that also contain sugars. Since sugars can also make people gassy, the combination with fiber is an extra potent one.
The reason that gassiness after eating fiber occurs starts in the intestinal tract. A normal, healthy adult eating a typical balanced diet will produce between 1 and 4 pints of gas in a given day. That same healthy adult will pass that gas an average of around 14 times per day, says National Digestive Diseases Information Clearinghouse data.
Gassiness after eating fiber or any other foods happens because bacteria living in the lower portion of the intestinal tract – often called the colon – consume carbohydrates that made it through the small intestine undigested. This causes the carbs to ferment and gas is a natural result of the fermentation process as the carbohydrates break down. With soluble fiber, this usually means a double-whammy as both the fiber and the sugars (such as sorbitol, fructose, raffinose and lactose) all ferment and produce gas.
The foods that contain soluble fiber – that is, the ones with the greatest potential to make you pass gas – include beans and lentils (also known as legumes), oats, nuts, barley, peas and the majority of fruits. Some veggies such as cabbage, broccoli, Brussels sprouts and cauliflower will also have the same effect.
Beans are particularly likely to cause a gassy reaction within the body because they contain a type of sugar that is quite challenging for the body to digest. It is called stachyose. Because it’s challenging for the body to digest, it therefore takes longer to ferment and has a greater gas-producing potential.
To help to reduce the effect, pay attention to the amount of fiber you eat. As you increase it, do so slowly to allow your intestines to properly adapt to the change in your diet. Suddenly increasing fiber will only lead to gassiness. Spreading out the increases over a number of weeks may help to avoid that impact.