Acacia gum

What it isGum arabic — a soluble prebiotic fiber from the acacia tree, sold as a supplement and used widely as a food emulsifier.

Why this oneIt is among the gentlest soluble fibers: slowly fermented, so it feeds colonic flora with less gas and bloating than inulin.

What limits itIt is a supplement, not a drug — evidence is soft, and effects on stooling are modest.