Research Methodology

About this page

SupplementFactStack.com™ publishes one Consumer Brief per supplement, rating each marketing claim on the published research. This page explains how we research, rate and list products, and how a manufacturer or reader can ask us to correct something.

Our briefs are written for adults. They are for general education only. They are not medical advice, and nothing here replaces a talk with your doctor or pharmacist.

SupplementFactStack.com™ is a FactStack™ Research, LLC educational brand. We earn commissions when you buy through the retailer links in our Where to Buy tables. Every retailer listed in those tables is an affiliate partner. The section on ratings and commissions below explains how we keep the two apart.

How we research a supplement

Each brief starts from a full evidence review of the supplement. Every supplement is re‑evaluated monthly, and each brief shows the date of its review.

1. We list every marketing claim sellers make for the supplement, from testosterone to sleep.
2. We search the published research for human trials, systematic reviews and meta‑analyses on each claim. We log every search with its result count, and list every study we include or exclude with the reason, in the manner of a PRISMA 2020 systematic review.
3. We check named reference sources: ten in all, including Cochrane, the NIH Office of Dietary Supplements, USP, NSF and ConsumerLab. Where one disagrees with us, we record why.
4. We rate how sure we can be. We use a modified version of GRADE, the system medical researchers use to grade evidence as high, moderate, low or very low certainty.
5. We check each key trial for bias with the Cochrane risk‑of‑bias tool, which asks whether a study’s design could skew its results.
6. We say plainly when evidence is weak. Briefs flag small, old, unrepeated, unreviewed (preprint) and industry‑funded studies, and name the funder when it is known. We also argue the case against our own conclusion, using the Bradford Hill criteria to ask whether a link is likely to be cause and effect.
7. We leave out claims with no human evidence. They are listed as not scored, never rated.

Every brief lists at least 19 outside sources, each linked to the specific study, record or page it relies on. Each brief shows its date and version number, and a newer version replaces an older one when the research or the product list changes.

How we check safety and regulatory statements

We publish a recall, warning letter, import alert, legal status or similar statement only after reading it in the issuing authority’s own record.

Every review checks ten regulators: the US FDA, California Proposition 65, Health Canada, the EU (EFSA, the European Commission and its RASFF alert system), the UK Food Standards Agency, Australia’s TGA, Singapore’s Health Sciences Authority and Japan’s Consumer Affairs Agency, plus Korea’s MFDS and Taiwan’s TFDA when the supplement has a tie to those markets. Regulators tell us about safety, legal status and permitted claims, never about whether a supplement works.

• Read at the source. Each such statement is checked on the agency’s own page or record, such as an FDA enforcement report or warning letter, and linked to that exact record.
• Translated records are labeled. When the record is in another language, the brief says “According to <agency> records (translated)”.
• Secondary reports are labeled or left out. A finding seen only in a news story or third‑party report appears, if at all, as “reported”, and never in a brief’s Bottom line.
• Allegations are called allegations. California Proposition 65 notices are filed by private enforcers. We describe them as allegations, not findings, and say when no amount has been published.
• Status is dated. Recalls and actions show the month and year, and briefs note when a recall was still listed as ongoing at a stated date.

The Manufacturer Recalls & Warnings table in each brief covers the last 36 months, newest first.

How to read our ratings

Each claim gets one word in each of five columns, and the FactStack™ Rating gives the overall result as Favorable, Caution or Warning. The ratings describe the research on the ingredient, never a particular product or brand.

• Colors follow the words: green for the strongest, yellow for the middle, red for the weakest and grey for TBD or Not Graded.
• Safety comes first. Any claim with a Safety Risk of Avoid is rated Warning, however strong its other columns.
• At a Glance boxes at the top of each brief repeat the row for the best‑supported claim.
• No scores are shown. The rating comes from a fixed scoring method applied the same way to every supplement: Supporting Evidence counts for 55%, Safety Risk for 30% and Product Quality for 15%, combined so that a weak rating in any one pulls the result down. We show the word, not the number.

How we build the Where to Buy tables

Where to Buy lists products from our affiliate retailers that hold at least one of NSF/ANSI 173, NSF Certified for Sport or USP Verified status or are made in the USA, with each criterion shown so you can decide for yourself. It is a list, not a recommendation.

• Retailers. Products come from Amazon, Botanic Choice, Green’s Nutrition, HerbsPro and iHerb. We review their catalogs twice a month, on the 15th and the 25th.
• Certifications come from the certifiers. NSF/ANSI 173, NSF Certified for Sport and USP Verified are marked only when the exact product appears in NSF’s or USP’s own public listing. A seal on a label or a retailer page is not enough on its own. A blank cell means we did not find a current listing.
• Made in USA comes from the seller. We record what the label, product page or brand site says. “Packaged in the USA” alone does not count, and those products are left out.
• Recall screen. We leave out a brand’s products for a supplement when, in the last 36 months, the FDA took action against that brand over that supplement: a Class I or II recall, a warning letter, an import alert or an advisory letter. We also leave out any brand with an FDA Class II recall or warning letter on any product, and any product named in a California Prop 65 notice or a non‑US recall, along with that brand’s products of the same ingredient and form. Brands with lesser actions on other products stay listed and are marked in the Recall Screen column.
• Order. Products are ranked by how many of the five criteria they meet, then by price, lowest highest.
• Duplicates. When the same product is sold by more than one retailer, we keep the lowest‑priced listing.
• Prices. Prices are as shown on the date of our product review and change often. Amazon prices are not shown, under Amazon’s rules; use the Check Price link.

How we keep ratings separate from commissions

Our ratings are set from the research before any products are added to a brief, and no brand or retailer can pay to change them.

• Order of work. Each supplement is researched and rated first. The product list is built separately and added to the brief afterward.
• No paid placement. No brand or retailer pays to be rated, listed or ranked, and none sees or approves our content before it is published.
• Commissions are disclosed. Every retailer in a Where to Buy table is an affiliate partner, and we say so at the top of each brief and under the table. Our affiliate partners across the site are Amazon, Botanic Choice, Everlywell, Green’s Nutrition, HerbsPro and iHerb.
• Records are kept. We keep dated records of each brief’s inputs, ratings and versions, and we archive older versions rather than deleting them.

How we use AI tools. We use AI tools to gather, check and summarize research and to build each page from fixed rules. Every brief passes an automated rules check before it is saved, and is reviewed by a person before it is published. Ratings come from a fixed scoring method applied the same way to every supplement, and any judgment call in scoring is logged for human review.

Corrections and disputes

If you believe something in a brief is wrong, email Inquiry@tabbycatllc.com we will review it and reply within 10 business days.

Who can write. Manufacturers, brand owners, retailers, researchers and readers. You don’t need to be a partner or customer.

What to send.

1. The brief’s name, its date and version (shown in the header), and the statement or table cell you dispute.
2. What you believe is correct, in a sentence or two.
3. Your evidence. For example: an NSF or USP listing for the exact product, a later status on an FDA record, a published study we missed, or a corrected label.
4. Your name, company and how to reach you.

What happens next.

1. Acknowledge within 3 business days, with a reference number.
2. Review against the original source records and the evidence you sent, within 10 business days. If a review needs more time, we tell you why and give a new date.
3. Decide and reply in writing, with one of three outcomes:
   • Corrected: we fix the brief and publish a new version.
   • Clarified: we add context or a date, such as a later recall status.
   • No change: we explain why, with the sources we relied on.
4. Record it. Every request and outcome is logged with dates.

How corrections appear. A corrected brief gets a new version number and date, and a short note in What’s New says what changed and when. Factual errors about a named brand or product are corrected as a priority, and the corrected page goes up as soon as it is ready.

What we never do. We never accept payment, free product or an affiliate deal in exchange for changing a rating, a listing or a correction outcome. Asking for a correction never affects a brand’s ratings, listing or ranking. A rating changes only when the research or the source records change.

Contact and page history

• General Questions, Corrections and disputes: Inquiry@tabbycatllc.com
• Mail: FactStack™ Research, LLC, 1750 HWY 160 W STE 101 BOX 112, FORT MILL, SC 29708
• This page: published October 20, 2026. When our methods change, we update this page the same day and note the change here.