What is the best 3rd party supplement testing?

Not detected means nothing without a number: the detection limit, the quantification limit, and why the method decides what a report's result means before the result is read

What is the best third-party supplement testing is a question that is answered by one number that most testing claims leave out, and once the number is understood the shelf's testing claims sort themselves. The number is the detection limit. Every analytical method has a lowest amount of a substance that it can detect, below which the substance is present or absent and the method cannot say which, and a report that reads not detected for lead has said only that the tub contains less lead than that method's limit, which may be a thousandth of the standard or ten times it. A testing claim that reads tested, laboratory tested, or not detected with no number beside it has made a statement whose meaning the buyer cannot know, and the best third-party testing is simply the testing whose report carries the numbers that give its results a meaning, which the good laboratories print as a matter of course and the testing claims on labels never do.

A good report carries four numbers for each thing it tested. The method, named by its technique and often its standard method number, because the method sets the limits; the laboratory's accreditation for that method on a food supplement or food matrix, which says an assessor watched it run and checked its validation, and which a buyer verifies in the accreditation register's schedule for that laboratory; the limit of detection and the limit of quantification for each analyte, the first being the lowest amount the method can see and the second the lowest amount it can put a reliable figure on, with results between the two reported as detected but below quantification; and the result against a stated specification limit, the number the brand or the regulation sets as the maximum, so that the buyer sees the figure, the limit and the margin. A report with all four is a measurement a buyer can rely on and compare between brands; a report missing the limits is read with that gap, and a label with none of the four is read as a claim.

The method decides what a result means before the result is read, and heavy metals are the clearest case. Inductively coupled plasma mass spectrometry detects lead, mercury, arsenic and cadmium at parts per billion, well below the specification limits the regulations set for a supplement, so that a not detected from that method on an accredited matrix means the tub contains a trace at most; an older or cheaper technique, with a detection limit at or above the specification, can report not detected for a tub that contains the contaminant below its own limit and above the standard, and the report is accurate and the tub is non-compliant at once. A buyer who reads the method first knows which not detected they are holding, and a brand that names its method has told the buyer which, which is the difference between the best testing and a word.

One number that turns a claim into a test and four that make a report readable, and what the best testing looks like analyte by analyte, how the report is obtained, what it still does not cover, and the worked example's own report read for its numbers, which is the next section.

What the best testing looks like for each thing tested, metals, microbes, assay and banned substances; how the report is obtained by lot; what the best testing still does not cover; the worked example's report; and the verdict

The best testing differs by what is tested, and each has its own standard. For heavy metals it is mass spectrometry on an accredited supplement matrix with a detection limit in parts per billion and the four metals, lead, mercury, arsenic and cadmium, each reported against the regulatory limit; the specification limits are low and a method that cannot see below them is the wrong method. For microbiology it is culture against the pharmacopoeial or food limits for total counts, yeasts and moulds and the named pathogens, with the detection limit expressed as the lowest count the plating can resolve and the pathogens reported as absent in a stated sample weight, since absent in one gram and absent in twenty-five are different statements. For the assay of the active it is a validated method for that nutrient on that matrix, chromatography for a vitamin or a marker compound, elemental analysis for a mineral, reported as a quantity per capsule against the label figure within the tolerances, with the method's uncertainty stated so the buyer knows whether 95 percent of label is a shortfall or the method's noise. For banned substances it is the certification programmes' screens, which test each lot against the prohibited list at the detection limits the anti-doping laboratories use and publish a pass by lot, and whose value lies in those limits being the ones a drug test would apply.

The report is obtained by lot, with an email to the brand quoting the lot number on the tub and asking for the certificate of analysis for that batch, and the reply is read for the four numbers before anything else: the method named, the laboratory named and found on the accreditation register with that method on its schedule, the detection and quantification limits printed beside each analyte, and the results against the limits. A brand whose certificate carries all four has the best testing available; a brand whose certificate reads not detected with no limits has testing whose meaning it has not shown; and a brand that sends a statement instead of a certificate has a claim. The same reading is applied to the testing pages on brand websites, which rarely survive it.

What the best testing still does not cover is stated so the number is not asked to do more than it can. A report describes the sample the laboratory received, and whether that sample represented the batch sold depends on how it was taken, which the report does not say and the buyer asks the brand; a report against a brand's own specification is only as strict as the specification, so a buyer reads the limit against the regulatory one; and a report says nothing about whether the product works, which is the evidence question answered elsewhere. The best testing proves the tub, with numbers, and the trials prove the nutrient, and a purchase needs both.

The worked example's own report is read for its numbers: {FL} has each batch tested for lead, mercury, arsenic and cadmium by inductively coupled plasma mass spectrometry at a UK laboratory accredited for that method on a food supplement matrix, with the detection limit stated for each metal on the certificate and the result reported against a stated specification limit, released by lot number on request, which is the four-number standard this page describes; the product is 1500mg magnesium bisglycinate stated as 300mg elemental at 80% NRV, released against specification in a UK facility certified to GMP and BRC, two capsules with the evening meal, 180 capsules for £19.99 at 22p a day, and not enrolled in a banned-substance programme, which the page states. The full label breakdown is here.

The verdict: the best third-party supplement testing is the testing whose report carries numbers, the method, the accreditation for it on a supplement matrix, a detection limit and a quantification limit for each analyte, and the result against a stated limit, because not detected means nothing until the lowest detectable amount is beside it. Heavy metals by accredited mass spectrometry in parts per billion is the standard, a cheaper method with a higher limit can pass a tub a better one would fail, and a certificate obtained by lot and read for its four numbers is the whole of the question.

What to check on the label

Questions people also ask

What does third-party tested really mean on a supplement?

On its own, nothing a buyer can measure: a testing claim becomes a test only when its report carries numbers, the method named by technique, the laboratory's accreditation for that method on a supplement matrix verified in the register's schedule, the limit of detection and the limit of quantification for each analyte, and the result against a stated limit; a report reading not detected has said only that the tub contains less than the method's limit, which may be a thousandth of the standard or ten times it, and a label reading tested with no number is a claim.

Why does the detection limit matter for supplement testing?

Because it is the number that gives a result its meaning: every method has a lowest amount it can detect, below which it cannot say whether a substance is present, so a cheaper method with a detection limit at or above the specification can report not detected for a tub that contains the contaminant below its own limit and above the standard, accurately and uselessly; heavy metals by inductively coupled plasma mass spectrometry are detected at parts per billion, well below the regulatory limits, which is why a report's method is read before its result and why the best testing states the limit beside every analyte.

What should a certificate of analysis include?

Four numbers for each thing tested: the method, named by technique and often its standard number; the laboratory's name, found on the accreditation register with that method on its schedule for a food supplement or food matrix; the limit of detection and the limit of quantification for each analyte, with results between the two reported as detected but below quantification; and the result against a stated specification limit, read in turn against the regulatory one; a certificate with all four is a measurement a buyer can rely on and compare, and one missing the limits is read with that gap.

Which supplement test is most important?

Heavy metals for a mineral or a soil-grown extract, by mass spectrometry on an accredited supplement matrix with a detection limit in parts per billion, because metals are the contaminant a buyer cannot see, taste or feel and the one that accumulates; microbiology for anything that could carry it; the assay of the active for anything where the dose is the point, reported per capsule against the label within tolerance with the method's uncertainty stated; and a certification programme's banned-substance screen at the anti-doping detection limits for anyone who is drug tested, since a screen at a higher limit than a drug test is not a screen.

What testing does this site's magnesium have and what are its numbers?

Each batch is tested for lead, mercury, arsenic and cadmium by inductively coupled plasma mass spectrometry at a UK laboratory accredited for that method on a food supplement matrix, with the detection limit stated for each metal on the certificate and the result reported against a stated specification limit, released by lot number on request; the product is 1500mg magnesium bisglycinate stated as 300mg elemental at 80% NRV, released against specification in a UK facility certified to GMP and BRC, at 22p a day, and it is not enrolled in a banned-substance programme, which a drug-tested athlete notes.

Sources

1. The heavy metals analysis literature: inductively coupled plasma mass spectrometry is the standard method for quantifying lead, cadmium, mercury and arsenic in dietary supplements against regulatory maximum levels. PubMed record
2. ISO/IEC 17025, the standard for testing and calibration laboratories: accreditation to it by a national body attests to a laboratory's technical competence and the validity of its results for the methods in scope, and is what makes a certificate of analysis a document someone has audited. https://www.ukas.com/accreditation/standards/laboratory-accreditation/
3. The official methods of analysis for dietary supplements: validated methods for the identity and quantity of vitamins, minerals, botanical markers and contaminants in supplement matrices, with the method's validation covering the sample type, which is why a laboratory names the method and the matrix on its report. https://www.aoac.org/official-methods-of-analysis/
4. The UK accreditation service's schedules of accreditation: each accredited laboratory holds a published schedule listing the specific tests, methods and sample types it is accredited for, searchable by laboratory name, so that accredited is a statement about named methods on named matrices rather than about the laboratory as a whole. https://www.ukas.com/find-an-organisation/

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