Prebiotics: Fiber Types, FOS, GOS, Inulin & Resistant Starch
Prebiotics are dietary substrates that selectively feed beneficial gut bacteria, promoting their growth and metabolic activity. While all prebiotics are fiber, not all fiber is prebiotic — the distinction is selectivity. True prebiotics preferentially stimulate the growth of beneficial species while not equally feeding pathogenic bacteria.
Major Prebiotic Types
- Inulin & FOS (fructooligosaccharides): Found in chicory root, Jerusalem artichokes, garlic, onions, bananas, and asparagus. These are the most studied prebiotics and primarily feed Bifidobacteria.
- GOS (galactooligosaccharides): Found naturally in breast milk and legumes. Strong bifidogenic effect.
- Resistant starch: Found in cooled potatoes, green bananas, and legumes. A potent producer of butyrate.
- Beta-glucans: Found in oats, barley, and mushrooms. Both prebiotic and immune-modulating.
- Pectin: Found in apples, citrus fruits, and berries. Supports diverse SCFA production.
Start slow: Rapidly increasing prebiotic intake can cause significant gas and bloating as gut bacteria adjust. Gradually increasing fiber intake over 2-4 weeks allows the microbiome to adapt.
For the differences between prebiotics, probiotics, and postbiotics, see the comparison page.