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SupplementAbsorption.comPreview · grades pending reviewer sign-off

Methodology

Sources

Studies are found in PubMed and Europe PMC. For paywalled papers we use the abstract only and link the source; free full text (PubMed Central) is used where available. 805 studies screened as off-topic for the launch supplements are excluded. Data last built 2026-10-31.

Verbatim quotes, no invented numbers

Every finding shown is copied word for word from the abstract or full text, tagged with where it came from (abstract, or the table/section of the full text). We do not compute, normalize or estimate absorption values. Extraction is automated and each quote is marked unverified until a human checks it against the paper.

Species labels

Studies are sorted human first, then primate, pig, rodent, other animal and in vitro. Animal and lab results may not apply to people.

  • Human — Study in people
  • Primate — Non-human primate study; may not apply to people
  • Pig — Pig study; may not apply to people
  • Rodent — Rat/mouse study; may not apply to people
  • Other animal — Animal study; may not apply to people
  • In vitro — Lab/cell study; not evidence of effects in people
  • Species unclear — Species not yet confirmed

Evidence grades (rubric v2, draft — pending reviewer)

Single-form human pharmacokinetic (PK) studies count. A form studied in many people gets a high grade even if nobody compared it head-to-head with another form.

1. Absorption evidence grade (per form)

Counts human single-form arms only (IV arms excluded). Consistency is the median coefficient of variation (CV) of the same PK parameter across studies under matched conditions.

  • A: ≥5 human studies, ≥100 participants in total, ≥2 randomized or crossover studies, and median CV ≤100% (or consistency not evaluable).
  • B: ≥3 human studies, or 2 consistent studies.
  • C: 1–2 human studies.
  • D: animal or in vitro data only.

Median CV ≤50% is consistent. 50–100% is heterogeneous but not penalized. Above 100% lowers the grade one step.

2. Form comparison grade (per pair)

  • Head-to-head studies weigh more. Their grade follows the A–D scale: A for 2+ agreeing human randomized/crossover studies, B for one, C for limited or conflicting data.
  • Matched single-form (indirect) evidence: A with ≥3 studies per form, B with ≥2, otherwise C, but only when ranges separate clearly under matched conditions (parameter, analyte, matrix with serum = plasma, fed state, dosing, AUC interval, baseline correction, units).
  • When both exist and agree, the pair takes the better grade. When they conflict, it drops one step below the better grade. A head-to-head finding of no difference is never overridden by indirect evidence.
  • Comparisons where baseline correction is not reported are capped at C.

The page grade is the best form or comparison grade. Grades are auto-computed drafts pending reviewer sign-off. With-food and best-time grades come from an earlier abstract screen and are labeled that way. This is not medical advice.

Calculator

Cost per mg uses only the price and label amount you enter. Cost per mg absorbed is shown only as a range, and only when a reviewer-verified fractional-absorption range quoted from a cited study exists for that form. We never show a single "mg absorbed" figure or suggest a dose.

Corrections

Found an error? Corrections contact to be added before launch.