Does eating beans of a mother cause flatulence on babies? Is it true that if you eat beans it could cause flatulence on babies (when breastfeeding them)? I can't find any research or scientific facts about that topic. I thought the body of the mother would filter "bad" ingedients.

When the mother eat beans, the fiber (oligosaccharides) from them is not digested in the small intestine, so it travels to the large intestine, where normal intestinal bacteria break it down to some absorbable nutrients (like short-chain fatty acids) and gas that is largerly expelled (fao.org). Some gas can be absorbed into the blood and then removed by the lungs (PubMed).

This means that neither the fiber nor the resulting gas ends up in the mothers breast milk, so it cannot give gas to the baby.

Breast milk contains human milk oligosaccharides (HMO). HMO is undigestible, but bacteria in the infant's intestine can break it down and produce gas. However, the amount of HMO in the breast milk is not likely related to the amount of beans or other high-fiber foods the mother consumes, but is genetically determined (PubMed).