A 200-gram serving of baked beans in tomato sauce could contain as much as 9.6 grams of sugar, per BBC Good Food. Excess sugar in your system can sit in your digestive tract and ferment, eventually becoming food for your gut bacteria, leading to gas buildup. Some people may experience cramping along with the gas.
There are other reasons why beans in general cause an increase in flatulence — their complex carbohydrate content, fiber profile, and lectins. Complex carbs are challenging to digest and need the help of gut bacteria to break them down, resulting in gas. While some amount of fiber is necessary to make you poop, too much or too big an amount consumed too quickly can also lead to flatulence. Bloating and gas are side effects of lectins too.
While all legumes could lead to flatulence, some are bigger trouble-makers in that department, per registered dietitian nutritionist Kelsey Kunik (via Eating Well). “Soybeans, pinto beans, black beans, and lentils are most likely to cause gas because of the amount of fermentable sugars and fiber,” explained the expert. Straining the canned goods in a colander or sieve and holding them under running water for a few minutes helps remove the added sugar component. But this is not all that gets removed during a good old rinse.