Research Methodology

Sources we use

Depending on the product, a guide may draw on:

• the product label and its Supplement Facts panel;
• the seller's own pages: the sales or order page, FAQ, terms, shipping policy, and refund or guarantee policy;
• the affiliate program's public information for the product;
• scientific literature, searched mainly in PubMed, and reference material such as the NIH Office of Dietary Supplements;
• public regulatory records, such as FDA and FTC search results;
• third-party records such as Better Business Bureau profiles or marketplace listings, when they matter to a buyer.

Not every source type is used for every product, and each guide lists the sources behind what it shows. Seller sources are labelled as seller sources; they tell us what the seller says, not what is independently true.

Label provenance

Where the label information comes from matters, so each guide says what we examined. It may be a physical label, or label artwork published by the seller, which can be current, partially verified or no longer displayed by the seller. When we did not examine a physical container, the guide says so, and it states other limits, such as a label panel without directions or warnings, or artwork the seller no longer shows. We never describe label artwork as a physical label we inspected.

Label facts, seller claims and research

We keep four kinds of information apart: what the label declares, what the seller claims, research on individual ingredients, and research on the finished product. Amounts inside a proprietary blend are not split among its ingredients when the label does not give them.

Scientific evidence

Ingredient studies often use different doses, extracts, populations, formulations or durations than a finished product, so they cannot by themselves establish what that product does. We note those differences where they apply. We also search for studies of the finished product itself; when our searches find none, the guide says that no study was identified in the searches we performed, and which database we searched.

Offer, shipping and refund research

We check the seller offer as it appears on the page the purchase link opens, without buying: package prices and their arithmetic, seller-described savings and reference prices, package labels such as "Most Popular", shipping, the guarantee and the refund conditions. Seller package labels and reference prices are attributed to the seller and are not our recommendation. When the seller's own figures or policies do not agree, we report the difference as it appears.

Check dates and freshness

Offers, labels and seller terms change. Each guide shows the date each part was checked, and those dates are not real-time. Prices are shown only while the price check is at most 30 days old, shipping and refund information while its check is at most 60 days old, and label information while its check is at most 180 days old. Purchase links are rechecked periodically; a purchase link whose check is more than 30 days old is removed from the page until it is checked again.