Reading a probiotic label
A guide meant for whichever bottle you are holding. SlimTide is the worked example, because its panel is complete enough to work through, but nothing here depends on it.
Four things make a probiotic label checkable: the genus, the species, the strain, and a colony-forming unit count at the end of shelf life. Most labels give you the first two. The last two are where the useful information is, and US regulations require neither.
Everything else on this page is how to read what the law does require: what a Supplement Facts panel must carry, how a proprietary blend’s descending order sets a ceiling on every ingredient inside it, and how to check a fibre amount against a published Daily Value.
What a Supplement Facts panel must carry
Start here, because everything a label is allowed to imply elsewhere is constrained by what it had to print here.
The Supplement Facts panel is the only part of a supplement label that is a measurement. The front of the bottle is marketing, the side panel is instructions, and the panel is the part where somebody had to commit to numbers.
FDA’s labeling guide sets out what it has to contain. The four requirements below are the ones that decide whether you can check anything at all.
- A serving size, and servings per container
- Everything else in the panel is per serving. A serving of two capsules in a 60-capsule bottle is a 30-day bottle, not a 60-day one, and this is the single most common way a label reads larger than it is.
- A quantitative amount per serving for each dietary ingredient
- The milligram, gram or microgram figure. This is the requirement that makes a label checkable, and it is the one a proprietary blend is permitted to sidestep.
- For a proprietary blend, the total weight of the blend
- On its own line, with the ingredients in it listed underneath in descending order of predominance by weight. No individual amount is required. What that buys you is covered further down this page.
- A footnote where no Daily Value has been established
- Printed as “Daily Value not established”, usually against a dagger. It is a statement about reference intakes, not about whether the ingredient does anything, and it is routinely misread as the second.
What a panel is not
It is not approval. FDA does not approve dietary supplements, and a complete, correct panel means the label complies with the labeling rules — not that the amounts in it do anything.
That is the whole trick of reading one well. A good panel tells you what is in the bottle accurately enough that you can compare it with published research yourself. The comparison is the part nobody does for you.
The four things a probiotic label should give you
Genus, species, strain, and a count at end of shelf life. Each one is useless without the one before it.
NIH’s Office of Dietary Supplements defines a probiotic as live microorganisms that, when administered in adequate amounts, confer a health benefit on the host. Four pieces of information are needed before you can tell whether a bottle meets that sentence, and they build on each other.
Genus — the first word
Lactobacillus, Bifidobacterium, Clostridium, Akkermansia. It is the broadest grouping and on its own it tells you very little. It matters chiefly as a warning: some genera contain species nobody wants to swallow, which is why the levels below it are not optional.
Species — the second word
Bifidobacterium infantis, Clostridium butyricum. Most labels get this far, and it is the point at which the organism becomes searchable. It is still not the level at which the research is indexed.
Strain — the letters and numbers after the species
MIYAIRI 588. ATCC BAA-835. DSM or CNCM followed by a number. This is the level at which probiotic effects are demonstrated. ODS is explicit that effects are strain-specific and that failing to take the strain into account produces misleading conclusions. A species name without a strain cannot be looked up against any trial, because the trial was run on a strain.
Colony-forming units, at the end of shelf life
CFU is the count of viable organisms — the ones capable of forming a colony, which is to say the live ones. ODS advises choosing products that state CFU at the end of the product’s shelf life rather than at the time of manufacture, because probiotics die during storage. A count at manufacture describes a moment you were not present for.
And one thing a count does not tell you
ODS also notes that products with higher CFU counts are not necessarily more effective than those with lower ones. A count is not a score.
It is the minimum information needed to compare a bottle with a trial. Without it no comparison is possible in either direction, which is a different complaint from saying the number is too small.
Why so many probiotic labels give you a weight
It is not a loophole somebody invented. It is what the rules ask for, and it is the thing to notice.
ODS states the position plainly: current US regulations require only that the total weight of microorganisms be listed on a supplement label, not a viable colony-forming unit count. A manufacturer may add a CFU figure voluntarily, and many do.
So a line reading Probiotic Blend — 36 mg is a compliant label. It is also a label that has told you the weight of a powder. Weight is the same whether the culture in it is alive or dead, and a probiotic is defined by being alive.
| What the label prints | What it lets you do |
|---|---|
| Probiotic Blend — 36 mg | Nothing quantitative about organisms. You know how much powder there is. |
| Probiotic Blend — 36 mg, with three species named underneath | You know which organisms, and — because the order must be descending by weight — a ceiling on each. You still cannot look any of them up. |
| The same, plus a strain designation for each | You can find the trials. You can check the safety record. A clinician can answer a question about it. |
| The same, plus CFU per serving at end of shelf life | You can compare the bottle with the dose the trials used, which is the whole point of the exercise. |
Scroll this table sideways →
The gap between the first row and the last is where nearly every probiotic purchase is actually decided, and it is invisible unless you know the rows exist.
Reading a proprietary blend as a ceiling
A blend hides the individual amounts. The order it prints them in does not.
FDA’s labeling guide requires a proprietary blend to carry the total weight of the blend on its own line, with the ingredients listed underneath in descending order of predominance by weight. That second requirement is quantitative, and almost nobody uses it.
If the blend totals T milligrams and an ingredient is printed in position k, then every ingredient above it weighs at least as much as it does. So k ingredients each weigh at least as much as the one in position k, and that one can weigh at most T divided by k.
| Printed position | The sum | Weighs at most |
|---|---|---|
| First | 36 ÷ 1 | 36 mg |
| Second | 36 ÷ 2 | 18 mg |
| Third | 36 ÷ 3 | 12 mg |
Scroll this table sideways →
On a 36 mg blend of three organisms, that is 36, 18 and 12 mg as ceilings. The third organism cannot be more than a third of the blend no matter what the marketing says about it, and the first is not guaranteed to be any particular amount at all.
- What the ceiling is good for
- Catching a blend sold on its last ingredient. If the interesting organism is printed fourth in a 50 mg blend, it is at most 12.5 mg and probably far less.
- What it is not good for
- Establishing a dose. A ceiling is an upper bound; the actual amount could be a hundredth of it. Never treat T divided by k as the amount present.
- Where the trick fails
- When ingredients are present at similar weights, or when the blend is only two items long, the ceiling is loose enough to be uninformative. It is still the only arithmetic a blend permits.
- A note on milligrams and organisms
- On a probiotic blend this whole calculation is about powder weight. Even a perfect split between three organisms would not tell you how many of any of them are alive.
Checking a fibre amount against a published figure
Two divisions, both of which can be done in your head at the shelf.
Fibre is the easiest ingredient on a supplement label to put in proportion, because FDA publishes a Daily Value for it: 28 g a day for adults and children four and over. Any declared fibre amount can be divided into that.
FDA also publishes a rule of thumb for reading its own labels: 5% of the Daily Value or less is low, and 20% or more is high. Those two thresholds turn a milligram figure into a judgement without needing any other information.
| Step | The sum | The result |
|---|---|---|
| Convert the Daily Value to milligrams | 28 g × 1,000 | 28,000 mg |
| Divide the declared amount into it | 211 ÷ 28,000 | 0.75% of a day |
| Compare with FDA’s 5% threshold | 0.75% against 5% | Well inside the band FDA calls low |
| Ask how many servings would reach 5% | 1,400 ÷ 211 | 7 capsules |
Scroll this table sideways →
The same two divisions work on any fibre supplement. If a bottle declares 5 g of fibre a serving, that is about 18% of the Daily Value and nearly at FDA’s high threshold. If it declares 200 mg, it is a rounding error.
Where a specific published intake exists for the specific fibre, use that instead of the Daily Value. For chicory inulin the European Union authorised its bowel-function claim only for food providing 12 g a day, which on a 211 mg capsule is 57 capsules. A named intake from a regulator that examined the evidence beats a general reference figure every time.
The order to do it in
Six checks, in the order that discards the most bottles soonest.
Find the panel and read the serving size first
Then multiply everything else by it in your head. A label that makes you work to find the serving size is telling you something about itself.
Look for a strain designation on every organism
Letters and numbers after the species name. If there is none, you cannot look the organism up, and no amount of front-panel copy changes that.
Look for CFU, and check which moment it describes
At end of shelf life is the figure worth having. At manufacture is worth less. Neither at all is the most common answer on a retail shelf.
Apply the blend ceiling to anything in a proprietary blend
Total weight divided by the position in the list. It takes five seconds and it occasionally ends the decision on the spot.
Put the declared fibre against 28 grams
And remember FDA’s own thresholds: 5% or less is low, 20% or more is high.
Read the storage line, and the one four lines below it
On a live-organism product this is not housekeeping. If a label asks for refrigeration in one place and a cool, dry place in another, you have found a real problem and the seller is the only one who can resolve it.
None of the six requires anything you cannot do standing up. Together they are the difference between choosing a probiotic on its panel and choosing it on its front label.
What none of this establishes
A checkable label is not a good product. It is a product you are able to have an opinion about.
Yes
- A complete panel means you can compare the bottle with published research
- A strain designation means you can find the trials and the safety record
- A CFU count at end of shelf life means you can compare the dose with the trials’
- A blend total means you can at least derive a ceiling
Settle this first
- A complete panel does not mean FDA approved anything — it does not approve supplements
- A strain designation does not mean that strain was studied for what you want
- A high CFU count does not mean a better product; ODS says so directly
- A ceiling is an upper bound and never an amount
The purpose of reading a label well is not to arrive at a verdict. It is to arrive at the point where the remaining questions are specific enough to ask a seller, a pharmacist or a doctor — and to notice when a bottle has made that impossible.
See the SlimTide packs
One, three or six bottles. The price is on the seller’s checkout page, because it is one of the few figures this site was never given — and a figure we were not given is not a figure we will print.
Shipping cost and delivery time were not supplied either, which matters more than usual on a product whose label asks for refrigeration. The guarantee is 60 days from purchase unless the sales page prints longer.
References
The sources behind the numbers on this page.
- U.S. Food and Drug AdministrationDietary Supplement Labeling Guide, Chapter IV: Nutrition Labeling · sourceWhat a Supplement Facts panel must carry, and the proprietary-blend rule: the blend's total weight on its own line with the ingredients listed underneath in descending order of predominance by weight.
- Office of Dietary Supplements, National Institutes of HealthProbiotics — Health Professional Fact Sheet · sourceThe definition of a probiotic, what colony-forming units are, the fact that US regulations require total microorganism weight rather than viable CFU, the advice to prefer products stating CFU at end of shelf life, strain specificity, and the safety record in immunocompromised people.
- U.S. Food and Drug AdministrationDaily Value on the Nutrition and Supplement Facts Labels · sourceThe Daily Value for dietary fibre is 28 g, and FDA's own rule of thumb that 5% DV or less of a nutrient per serving is low and 20% or more is high.
- European UnionCommission Regulation (EU) 2015/2314 of 7 December 2015 authorising a health claim made on foods · source“Chicory inulin contributes to normal bowel function by increasing stool frequency”, authorised only for food providing a daily intake of 12 g of native chicory inulin. The source of the 12 g figure used throughout this site.