Prebiotics are food components that feed gut bacteria rather than acting on the body directly. The bacterial shift they cause is well documented, dose-related, and reverses within a fortnight of stopping. Measured benefits are small, largest where blood sugar control is already impaired. Costs are mostly gas, bloating, and loose stools. Most research is industry-funded, and reviewer confidence is low. (Full Review)
| Marker | Target | Why |
|---|---|---|
| HbA1c | 4.8–5.4% | Primary efficacy endpoint; the best-evidenced effect |
| Fasting glucose | 75–86 mg/dL (4.2–4.8 mmol/L) | Moved most reliably in trials, and cheap to repeat |
| Fasting insulin | 2–5 µIU/mL | Detects insulin resistance improvement earlier than glucose does |
| LDL-C | < 100 mg/dL (2.6 mmol/L), lower with plaque | Captures the modest lipid effect |
| Triglycerides | < 80 mg/dL (0.9 mmol/L) | Second lipid endpoint, and the more fermentation-sensitive one |
| hs-CRP | < 1.0 mg/L, optimally < 0.5 mg/L | Tracks systemic inflammation, the proposed downstream benefit |
| ALT | < 25 U/L (men), < 20 U/L (women) | Directly responsive endpoint in fatty liver disease |
| Alkaline phosphatase and bilirubin | ALP 50–90 U/L; total bilirubin 0.2–1.0 mg/dL | Safety screen for impaired bile flow before high-dose use |
| 25-hydroxyvitamin D | 40–60 ng/mL (100–150 nmol/L) | Determines whether increased calcium absorption can be used |
| Bone mineral density | No established target for this intervention; track change from the individual's own baseline | The only hard skeletal outcome with supporting trial data |
Cadence: Baseline panel before starting, rechecked at eight weeks, then annually. Glucose is monitored more closely for the first six weeks on insulin or a sulfonylurea. Bone density, where relevant, is a two-year interval measurement.