Supplement Label Index

Glossary

30 technical, regulatory and statistical terms used across Supplement Label Index, each with a plain-language definition, a real example, and links to where it shows up on the site.

Form & bioavailability

Bioavailability
The proportion of a declared dose that actually gets absorbed into the bloodstream in a usable form. Different chemical forms (salts, extracts, formulations) of the same compound can have very different bioavailability even at an identical declared dose -- the whole reason this site tracks "form," not just "amount."
Example: A 2011 randomized trial found a curcumin phytosome formulation raised total curcuminoid absorption roughly 29-fold compared to the same unformulated curcuminoid mixture -- yet 98.1% of on-market curcumin products with a matched form (1,962 of 1,999) are plain curcuminoids or an unspecified curcumin extract; only 1.9% name a phytosome-type formulation.
Chelate / chelated mineral
A mineral bound to a molecule at two or more points, forming a ring; in supplements the ligand is usually an amino acid such as glycine, as opposed to an inorganic salt (like oxide or carbonate). Chelation is marketed as improving absorption, and some chelated forms genuinely do outperform their inorganic counterparts in trials -- but "chelated" isn't a single defined compound, and quality varies by which chelating agent is used and how.
Example: Magnesium glycinate (a glycine chelate) is rated Tier 1 on our scale, on the strength of limited evidence; "magnesium amino acid chelate," a vaguer label declaration, is Tier 2 -- lower serum and salivary magnesium than citrate in the same trial, and "amino acid chelate" isn't one specific compound.
Curcuminoids
The umbrella term for curcumin and its two related pigment compounds (demethoxycurcumin and bisdemethoxycurcumin), all naturally present in turmeric root. A label reading "Curcuminoids 500mg" describes this baseline, concentrated-but- unmodified material -- not a formulation engineered to help the body absorb it, like a phytosome.
Example: 98.1% of on-market curcumin products with a matched form are plain or unspecified curcuminoids, the baseline, lowest-absorption form; only 1.9% name a phytosome-type formulation.
Quality tier
Our own 1-3 rating (not an official grading system) for how well a specific chemical form of a compound is supported by absorption or efficacy research relative to other forms of the same compound. Tier 1 is the best-evidenced form (bioavailability or clinical outcome), Tier 2 is acceptable, and Tier 3 is a low-cost, low-bioavailability form. "Unrated" means we found no comparative study for that form, or the label names no form and the compound's default form carries no rating.
Example: Magnesium citrate is Tier 1 (it produced the highest serum and salivary magnesium response in a head-to-head trial); magnesium oxide is Tier 3 (virtually insoluble, ~43% soluble even under peak gastric acid).
Standardized extract
A botanical extract guaranteed to contain a minimum percentage of a specific "marker" compound believed to drive the plant's effects (e.g. withanolides in ashwagandha, curcuminoids in turmeric). An unstandardized extract or raw powder carries no such guarantee -- it may contain a similar compound at a much lower, unknown concentration.
Example: Only 3.2% of on-market ashwagandha products (70 of 2,159 with a recognised form) are labelled as a standardized extract of >=5% withanolides, the material used in a widely cited 64-person trial (Chandrasekhar 2012); 49.6% are plain root powder or do not name a form (the site assigns those to root powder), neither of which guarantees withanolide content.
Withanolides
The class of steroidal lactone compounds in ashwagandha root believed to drive its stress-reduction and other studied effects. Standardized ashwagandha extracts guarantee a minimum withanolide percentage; plain root powder and unstandardized extracts do not.
Example: A widely cited ashwagandha trial (Chandrasekhar et al. 2012, n=64) used a high-concentration, full-spectrum extract standardized specifically for withanolide content.

Label & market structure

cGMP (current good manufacturing practice)
The FDA's manufacturing-quality rules for dietary supplements (21 CFR Part 111), which cover how a facility controls ingredients, equipment, testing and records. A recall that cites cGMP deviations is about the process that made a product rather than a single contaminant found in it.
Example: FDA enforcement records often cite cGMP in the reason for a recall, for example "CGMP Deviations: Intermittent exposure to temperature excursion during storage."
Excipient
Any ingredient in a supplement other than the active compounds -- fillers, binders, coatings, colors, and sweeteners. Excipients are declared in a label's "other ingredients" section, separate from the Supplement Facts panel's active ingredients.
Example: Titanium dioxide, a white color additive, appears as an excipient on 4,518 on-market products despite being removed from the EU's authorized food additives in 2022.
Formula Twins (exact-twin / near-twin)
Our term for a cluster of products sharing an identical formula across multiple brands. An "exact-twin" cluster requires every compound, form, rounded elemental amount, and serving size to match precisely; a "near-twin" cluster relaxes the match to the same compounds and forms and the same serving size, ignoring the declared amounts.
Example: 4,192 exact-twin clusters cover 17.0% of on-market products; loosening the match to near-twin raises that to 27.8%.
On-market / off-market
DSLD's own status flag: "on-market" products are listed as currently marketed, and "off-market" products carry an Off Market flag or date (discontinued or withdrawn). The status may lag real-world retail availability.
Example: Of 214,780 total labels ever recorded in DSLD, 121,959 are currently on-market and 92,821 are off-market.
Private label / contract manufacturing
A manufacturing model where a contract manufacturer produces a stock formula and packs it under each customer brand's own label ("private label" or "OEM" manufacturing). It's a normal, legal, and common way simple, commodity formulas reach the market, and one reason the exact same formula can appear under many different brand names -- though our data only show identical declared formulas, not who manufactured them.
Example: 212 products, sold under 91 different brand names, share the exact same "Super CoQ-10 100 mg" formula -- one of 4,192 such exact-formula clusters covering 17.0% of the on-market catalog.
Proprietary blend
A group of ingredients listed together under one combined name and total weight, without disclosing how much of each individual ingredient is inside. Proprietary blends are legal, but they make it impossible to know the dose of most individual ingredients inside the blend from the label alone (required nutrients such as vitamins and minerals still carry their own amounts).
Example: 27.2% of on-market products (33,203 of 121,959) declare at least one proprietary blend -- see the full breakdown, including which compounds are most often hidden inside one, on the Proprietary Blends report.
Reformulation
A product whose declared dose of a tracked compound changed by 20% or more between two DSLD releases, either on the same DSLD id or on a relaunched label with the same brand and name but a new id -- a real, if imperfect, signal that a manufacturer changed a product's recipe rather than simply re-submitting the same label.
Example: Cases are listed on the Reformulations report once two different DSLD releases have been compared (none yet).
Serving order / multi-column label
Some labels declare different amounts for different serving sizes in separate columns (e.g. "per 2 tablets, ages 4-8" and "per 4 tablets, ages 9+"). Every per-product dose figure on this site (except the Formula Twins comparison) uses only the label's first serving column, so a nutrient isn't double-counted by summing across age-specific columns that describe the same product.
Example: This convention is why every per-product dose total on this site, from compound pages to the dose-percentile tool, reads the same regardless of how many serving columns a label happens to declare.
Serving size (units per serving)
The amount a label treats as one serving, which for capsules, tablets, softgels and gummies is a count of units -- often more than one. Every "per serving" amount on a Supplement Facts panel describes that whole serving, not a single capsule, so a "400 mg" line on a four-capsule serving is 100 mg per capsule.
Example: A label listing 400 mg of magnesium per serving where the serving is 4 capsules delivers 100 mg per capsule; taking one capsule delivers a quarter of the listed amount.

Data & methodology

Decile
One of ten equal-sized groups a sorted data set is divided into -- the 10th, 20th, 30th... percentile cut points. Compound pages chart dose deciles to show the full shape of the market's dose distribution, not just a single median number.
Example: Magnesium's dose deciles run from a 10th-percentile dose well below the RDA up to a 90th-percentile dose that starts to approach it.
DSLD (Dietary Supplement Label Database)
The NIH's public database of dietary supplement labels, the main source behind the label counts on this site (recall, regulatory and reference-dose figures come from the additional sources listed on the Sources page). DSLD is survey-sourced plus voluntary manufacturer submissions -- not an exhaustive market census -- and every value in it is manufacturer-declared on the label, not independently lab-tested.
Example: The current analysis is based on the January 16, 2026 DSLD release, covering 214,780 labels ever recorded.
FDA recall classification (Class I, II, III)
FDA's rating of how serious a recalled product's problem is. Class I is a situation where there is a reasonable probability that using the product will cause serious adverse health consequences or death; Class II is where use may cause temporary or medically reversible adverse health consequences, or the chance of a serious outcome is remote; Class III is where use is not likely to cause adverse health consequences. The class describes the hazard, not the size of the recall.
Example: A Class II recall for an undeclared allergen and a Class III recall for a labeling error can both involve the same number of bottles.
Lift (statistical association)
The ratio of how often two things actually occur together to how often you'd expect them to occur together by chance alone, given how common each one is individually. A lift of 1.0 means no relationship; above 1.0 means the pair travels together more than chance predicts; below 1.0 means less.
Example: Chondroitin and Glucosamine are declared together 35.46x more often than chance would predict (995 products) -- the highest lift among the compound pairs we track that appear together in at least 100 products.
Median
The middle value of a sorted data set -- the 50th percentile. Used for dose statistics on this site instead of the average (mean) because a handful of extreme outlier doses can skew an average without affecting what a "typical" product actually looks like.
Example: The median declared magnesium dose across on-market products is 80mg elemental magnesium, well below the 420mg adult RDA.
Meta-analysis
A study that statistically combines the results of multiple independent trials on the same question, generally considered stronger evidence than any single trial alone. Several of this site's studied-dose citations are meta-analyses covering dozens of underlying trials and thousands of participants.
Example: A 2013 meta-analysis of 19 randomized trials and 1,683 subjects (trial doses roughly 0.1-5mg) is the main citation behind the 0.5-5mg studied dose range we use for melatonin.
Momentum score
Our own measure (not an official metric): the number of products containing a compound or excipient that entered DSLD in the last 12 months divided by the number that entered in the 12 months before. Above 1 means it is appearing on more new labels than a year earlier. Used to power the Trending pages.
Example: See which compounds and excipients currently have the highest momentum score on the Trending report.
Percentile
The value below which a given percentage of a data set falls. The 90th percentile of declared doses for a compound is the dose that's higher than 90% of products declaring it, and lower than the remaining 10%.
Example: Compound pages with enough dose data (all except probiotics) have a "Where does your dose rank?" tool that looks up the whole-number percentile for any dose you enter, using the same underlying percentile data.
PMID (PubMed ID)
The unique identifier PubMed (the National Library of Medicine's biomedical literature database) assigns to an indexed study. Every citation with a PMID on this site can be looked up directly at pubmed.ncbi.nlm.nih.gov/ followed by the PMID (for example pubmed.ncbi.nlm.nih.gov/23691095/) to read the original study.
Example: Ferracioli-Oda et al.'s melatonin meta-analysis carries PMID 23691095.
Randomized controlled trial (RCT)
A clinical study design that randomly assigns participants to a treatment or control (placebo) group, the standard for establishing whether a treatment actually causes an observed effect rather than merely correlating with it. Cited throughout this site's compound reference data as the basis for dose ranges and form-quality ratings.
Example: A 2003 RCT (n=46) comparing three magnesium preparations (citrate, oxide, amino-acid chelate) with placebo found citrate produced the highest serum and salivary magnesium levels, and that citrate and amino-acid chelate were absorbed better than oxide (by urinary excretion).
UPC (Universal Product Code)
The barcode number printed on a retail package (DSLD stores it in a combined UPC/SKU field). A UPC generally identifies one specific product and pack size, which makes it a much more reliable way to match a label to another record (such as an FDA recall notice) than a product or company name.
Example: A recall notice that lists a product's UPC can be matched to the DSLD label carrying the same UPC, without relying on similar-looking product names.

Dose & reference values

Elemental amount
For a mineral sold as a compound salt (e.g. magnesium oxide, zinc citrate), the mass of the actual mineral itself, excluding the weight of whatever it's bound to. A label declaring "1000mg magnesium oxide" is not the same as "1000mg of magnesium" -- oxide is only about 60% elemental magnesium by weight. Every mineral dose comparison on this site is normalized to elemental amount so different salts of the same mineral are comparable; other nutrients are put on a common unit basis, such as mcg RAE for vitamin A or mg NE for niacin.
Example: Magnesium oxide is 60.3% elemental magnesium by weight; magnesium glycinate is only 14.1% elemental magnesium, so a much larger total compound mass is needed for the same elemental dose.
Fairy-dust threshold
Our own reference cutoff (not an official regulatory term): 20% of the low end of the studied dose range in our reference data. A product declaring less than that is unlikely to reproduce any tested effect. It still legally lists the ingredient; it just does so at a token amount. A few compounds have no threshold.
Example: 33.2% of on-market magnesium products fall below magnesium's fairy-dust threshold of 48mg (20% of the 241mg low end of its studied dose range).
RDA (Recommended Dietary Allowance)
The average daily intake level of a nutrient sufficient to meet the requirements of nearly all (97-98%) healthy people in a given life stage and sex group, set by the National Academy of Medicine. It's a target for adequacy, not a safety ceiling -- that's what the Tolerable Upper Intake Level is for.
Example: Magnesium's RDA for adults 31 and older is 420mg (men) / 320mg (women); it is 400mg / 310mg at ages 19-30. 94.7% of on-market magnesium products declare less than 420mg (the adult male RDA) in a single serving.
Tolerable Upper Intake Level (UL)
The highest average daily intake likely to pose no risk of adverse health effects for almost all people in a life stage/sex group, set by the National Academy of Medicine. Exceeding a UL is not automatically unsafe for a given individual -- ULs are conservative, population-level thresholds, not a bright line between safe and unsafe.
Example: 29.5% of on-market niacin products declare more than the adult upper limit of 35mg niacin in a single serving -- by far the highest share of any compound we track this way.

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