How Distil works.

Public evidence-review protocol.

Most supplement companies do not publish their methodology because hiding the reasoning is how they sell more. Distil's commercial position is the opposite of that. We earn when you are informed, not confused. So this page exists.

What follows is the actual rulebook: the compound database, the grading system, the exclusions that are off the table by rule, the personalisation pipeline, the independent safety check, and the limitations of what an evidence-graded report can and cannot do. All of it checkable.

The compound database.

Distil's database holds 98 compounds. There are thousands of supplements on the market. Most do not have enough peer-reviewed clinical evidence behind them to justify a recommendation. The 98 are the ones that do.

Every compound is graded A, B, or C against the published research, by the rules below. Anything that does not reach Grade C is not in the database. Anything that drops below Grade C in a future review is removed. The database is a curated set, not a comprehensive index.

What the grades mean.

Grade A. Multiple high-quality randomised controlled trials, or one or more meta-analyses, demonstrating the claimed benefit in human populations relevant to who might take it. The effect size is meaningful, the evidence has been replicated, and the finding is consistent across independent research groups. Example: Magnesium for sleep onset, Omega-3 for cardiovascular risk markers, Vitamin D for deficiency-corrected bone health.

Grade B. Solid clinical evidence, typically several human RCTs with consistent direction but smaller sample sizes, or one strong RCT supported by clear mechanistic understanding. Less fully replicated than Grade A but well-supported. Example: L-Theanine for stress-related arousal, Saffron for mild-to-moderate low mood, Ashwagandha (KSM-66) for sleep quality and subjective stress.

Grade C. Emerging evidence. A small number of human RCTs, or strong mechanistic and animal-model evidence with limited human replication. Reported as emerging in every report it appears in. Always flagged so the reader can decide whether the evidence threshold is enough for them. Example: NMN/NR for NAD+ raising in over-45s, Fisetin for senolytic activity, Urolithin A for mitochondrial function.

Grade D. Never recommended. Used in the database internally to mark compounds we have considered and rejected, so the same decision does not get re-litigated each review. Compounds in this category have either failed to replicate, shown null results in well-powered trials, or carry a safety profile that makes the benefit-to-risk ratio untenable. Grade D compounds are listed in the database with the reason, but they never appear in a recommendation.

Mixed grades use the lower badge.

A compound with Grade A evidence for one outcome and Grade B evidence for another is treated as Grade B in any report where the Grade B claim is the relevant one. The reader sees the lower of the two grades, never the higher. This is a deliberate under-claim rather than an over-claim.

Hard exclusions, off the table by rule.

Some compounds are excluded for specific clients regardless of how well they would otherwise score. The exclusions are absolute, not "use with caution":

• 5-HTP on SSRI, SNRI, or MAOI medication. Serotonin syndrome risk. Hard exclusion, no exceptions.
• NMN or NR with any cancer history. NAD+ raising compounds may support cancer cell proliferation. Hard exclusion.
• Iron without confirmed ferritin in the deficient range. Iron supplementation in a non-deficient person carries real oxidative-stress risk. We do not recommend iron unless a blood result confirms the need.
• High-dose biotin (over 5,000 mcg). Always flagged for interference with thyroid function tests and troponin assays used in cardiac diagnostics.
• St John's Wort. Grade D. Never recommended due to CYP3A4 induction interfering with oral contraceptives, SSRIs, warfarin, statins, and immunosuppressants.
• Cancer treatment in progress. No supplement stack is produced. The intake form gates this answer before any payment is taken.
• Pregnancy or breastfeeding. Same. Defer to NHS antenatal prescribing and your midwife or health visitor.

There are more. The full list lives in the database itself. The principle is consistent: the report does not produce output we believe is unsafe for the specific client, even if the client wants it. The answer is sometimes "not for you, not yet, here is what to test first".

How a compound earns its place.

A compound enters the database only after a structured evidence review. The protocol:

One. A literature search across PubMed: meta-analyses and systematic reviews first, then primary RCTs in the relevant outcome and population. Mechanistic-only evidence does not qualify a compound for inclusion.

Two. Each citation supporting the entry must have a verified PubMed identifier (PMID). Citations written from general knowledge alone are not acceptable. The PMID is the auditable trace.

Three. A grade is assigned by the rules above, against the evidence. Grade is determined by what the published research actually supports, not by what the compound is marketed for.

Four. Population modifiers are documented. A compound that works for older adults may not work for younger ones. Effective doses for women may differ from doses for men. The database holds these qualifiers explicitly so the personalisation step can apply them.

Five. Drug interactions are checked against the master table and added to the entry. Any interaction that would make the compound dangerous on a common medication is written into the exclusion logic.

Six. A "Last PubMed review" date is stamped on the entry.

The database is recalibrated every quarter. The cadence is enforced by an automated forcing function: on the first day of January, April, July, and October, a GitHub workflow opens a tracked issue requiring the calibration to be completed before the issue closes. The full log of every calibration appears at the bottom of this page.

The personalisation pipeline.

A report is not a search of the database. It is a personalised stack built for one specific person, against their full health profile. The pipeline runs in five stages:

Compound scoring. Every compound in the 98-compound database is scored against the client's profile: their goals, their conditions, their medications, their diet, their sleep, their bloodwork, their lifestyle, the supplements they already take. Most compounds do not score high enough to be included. Selectivity is the product.

Clinical safety cull. A second pass removes any compound that survived the first pass but fails clinical justification on closer inspection. This includes medication interactions, contraindicated conditions, and risks specific to the client's age or population.

Dose-locking. For every compound that survives both passes, the personalised dose is fixed, against the client's specific conditions and medications. Anticoagulants cap doses of certain compounds. CKD changes thresholds. Pregnancy (where the report is generated, not gated) constrains forms. Dose-locking is the safety-critical step.

Personalised writing. The report itself is written section by section, against the locked manifest. The same compound recommendation appears identically in the introduction schedule, the daily timing table, the compound card, the interactions summary, and the sleep stack where relevant. Cross-section drift is engineered out by architecture, not editorial review.

Independent safety review. A second model, separate from the one that wrote the report, reviews the output against a full safety checklist: dose caps, exclusion rules, medication flags, language standards, missing GP review notices, banned-claim language. The check is fail-closed: any critical failure holds the report for manual review and prevents delivery.

The independent safety check.

The safety check is the most important step. It runs as a separate model call after the report is generated. It does not write the report; it audits it. If anything fails, the report does not deliver. It is held until reviewed.

A failure can mean a dose that exceeds a safety cap. A compound that should have been excluded for a stated condition. A claim that crosses from "may support" into "will". A missing GP review notice on a compound that requires one. An interaction that was not flagged.

When a report holds, an alert reaches Sebastian directly. The report is reviewed, rebuilt if necessary, and only delivered when it passes. This has happened. Reports that were technically deliverable but visibly imperfect have been rebuilt rather than shipped.

The QC stage is the reason Distil reports can be trusted. It is the difference between an LLM-generated supplement guide and a clinical-grade artefact.

What Distil deliberately does not do.

The boundaries are as important as the methodology:

We do not sell supplements. We do not stock supplements. We do not have an associated brand of supplements.

We do not take affiliate commission from any retailer.

We do not recommend specific brands. The reports tell you what the product needs to contain (the form, the dose, the purity certifications, the things to avoid). You buy it from whoever you trust.

We do not run a subscription. The report is a one-time purchase. If your situation changes, you can buy a refresh. We do not auto-renew, and we do not email you reminders to come back.

We do not include affiliate-bait compounds purely because they sell well. The selection is dictated by the evidence score, not by what would generate the highest cart value.

Naming what we do not do is part of the brand. Most supplement companies cannot honestly make these statements. Saying it directly is the point.

What this is, and is not.

Distil reports are personalised, evidence-graded information. They are not medical advice.

A Distil report does not replace a GP, a registered nutritionist, or a specialist. It does not diagnose or treat any condition. Where the report identifies that a condition or medication interacts with a compound, the report flags it and recommends discussion with your GP. Where bloodwork is the right next step before supplementation, the report says that.

Compounds are graded against published clinical research. That research has limitations. Sample sizes vary. Effect sizes vary. Replicability varies. The grade reflects what the evidence supports, but no Grade A claim is "this will work for you specifically". It is "the research suggests this tends to support this outcome in populations relevant to your profile".

Honest framing is part of the brand. Anyone who promises more than this is selling something else.

Reassessment, and what comes next.

The report you receive is built against the profile you submit. Profiles change. Conditions emerge. Medications start and stop. Children happen. Goals shift. The report includes a 12-week reassessment framework so you know what to track and when to revisit.

Returning customers within six months pay £49 for a refreshed report (the same as the founder pricing rate); after six months it is the standard rate. There is no auto-renewal and no reminder email. You decide when, or whether, to come back.

Two changes are coming:

A named clinical reviewer. An Association-for-Nutrition registered nutritionist will join as the named clinical reviewer of every Distil report. Their qualifications, registration number, and review responsibilities will be on this page when the relationship is signed.

Continued public log. Every quarterly calibration is documented in the calibration log below. The cadence is enforced automatically: a GitHub workflow on the first of each calibration month opens an issue that stays open until the calibration is complete. If a quarter passes without a new entry, it is publicly visible here.

Calibration log.

Every quarterly calibration of the compound database is logged here. The most recent calibration is at the top.