Prebiotics

What it does

Prebiotics are fermentable fibers (inulin, fructooligosaccharides, galactooligosaccharides) that feed beneficial gut bacteria and drive production of short-chain fatty acids like butyrate. Mechanistically solid and cheap, but clinical endpoint results are modest and vary by fiber type.

What the research says

• Increase beneficial gut bacteria and short-chain fatty acid production

  Evidence: moderate. Inulin, FOS, and GOS RCTs consistently show bifidogenic effects and higher SCFA output

• Modest metabolic benefits (glucose, satiety, triglycerides)

  Evidence: emerging. Small RCTs with heterogeneous results across fiber types and baseline diets

Mechanistically sound and very safe, but human clinical endpoints are modest, highly variable by fiber type and baseline diet, and less impressive than the mechanism suggests.

Is it worth it?

Cheap and safe; food sources (vegetables, legumes, whole grains) are an even better buy than powders.