Labels
Daily Values, and what a percentage is a percentage of
Two rows on this panel carry percentages, and both are right. Niacin at 20 mg is printed as 125%, and the FDA’s Daily Value for niacin is 16 mg — 20 over 16 is exactly 1.25. Zinc at 11 mg is printed as 100%, and the Daily Value for zinc is 11 mg. Correct arithmetic is worth saying out loud, because it often is not. This post is about what those percentages are percentages of, and what they leave out.
Two percentages, both correct
Check them yourself; it takes ten seconds each. The FDA publishes the Daily Values used on Nutrition and Supplement Facts labels. Niacin’s is 16 mg. Twenty divided by sixteen is 1.25, printed as 125%. Zinc’s is 11 mg. Eleven divided by eleven is one, printed as 100%.
This is a low bar and a surprising number of labels fail it, so the credit is real. Both rows also state the chemical form, which is more than required: Vitamin B3 (as Niacin) and Zinc (as Zinc Oxide). The second of those is a genuinely informative disclosure and we will come back to it.
What the two rows do not do is cover the capsule. Together they account for 31 mg of the 601 mg declared — about 5%. The other 95% is a proprietary blend with no individual amounts, so there is nothing to compute a percentage of. Every percentage on this panel describes a twentieth of what is in the bottle.
What a Daily Value actually is
A Daily Value is a single reference figure, set by the FDA, used to put a nutrient amount into proportion on a label. It exists so that a shopper can compare two products without carrying a reference table, and it is deliberately one number rather than a set of them.
That design has consequences a reader should hold on to. A Daily Value is not a dose for you specifically: it does not vary by age, sex, body size, diet or anything else about the person holding the bottle. It is not a target to be hit, and it is not a ceiling. And it is not a statement that the nutrient does anything at that amount — it is a reference point for labelling, nothing more.
So 100% of the Daily Value means the serving contains the reference amount. It does not mean the serving covers your needs, that you were short of it, or that more would be better. It means one division came out at one.
The Daily Value also only exists for substances that have one. That is the whole mechanism behind the third row on this panel: the FDA requires individual weights for ingredients with an established Daily Value, and does not for the rest. L-citrulline, L-carnitine, pine bark, maca, grape skin and saffron have none, so none of them carries a weight. The two percentages on this label and the six missing amounts are two sides of the same rule.
Why 125 per cent is not a warning
A figure over a hundred looks like an overdose and usually is not. A Daily Value is a reference, so exceeding it is an ordinary event: a bowl of fortified cereal exceeds several before breakfast.
What a percentage over a hundred should prompt is a different question, with a different number behind it: how far is this from the Upper Intake Level? The Daily Value says where the reference sits. The Upper Intake Level says where caution begins. They are set by different bodies for different purposes and they are easy to confuse because both get quoted in milligrams.
| Nutrient | On this label | Daily Value | Tolerable Upper Intake Level | Headroom |
|---|---|---|---|---|
| Vitamin B3 (as Niacin) | 20 mg · 125% | 16 mg | 35 mg for adults, from supplements | 15 mg |
| Zinc (as Zinc Oxide) | 11 mg · 100% | 11 mg | 40 mg for adults | 29 mg |
Both rows sit comfortably below their upper levels, and that is the useful conclusion: 125% of a Daily Value is not the number to be uneasy about when the Upper Intake Level is 35 mg and the serving is 20 mg.
There is a third number for niacin, and it belongs here because it is the one people actually notice. The NIH writes: “Thirty to 50 mg or more nicotinic acid typically causes flushing; the skin on the patient's face, arms, and chest turns a reddish color because of vasodilation of small subcutaneous blood vessels.” At 20 mg this capsule is below that threshold. The complication is that the label says “niacin” without saying which niacin — nicotinic acid and niacinamide are both covered by the word and only one of them flushes. At this amount it is unlikely to matter; the naming convention still covers two different compounds.
Content is not absorption
Here is the part a percentage genuinely cannot tell you, and the label deserves credit for making it visible at all.
A Daily Value percentage always describes content: how much of the nutrient is in the serving. It says nothing about how much of that gets across the gut wall. That is true of every supplement on every shelf, and it is not a trick. It becomes interesting only when the label tells you the chemical form — and this one does.
NIH Office of Dietary Supplements — Zinc
“Absorption of zinc from supplements that contain zinc citrate or zinc gluconate is similar, at approximately 61% in young adults; the absorption from supplements that contain zinc oxide is 50%.”
So the 100% on this panel is 100% of the zinc in the capsule, in the form with the least favourable figure of the common ones: 50% against roughly 61% for citrate or gluconate. Nothing about the label is misleading here. The percentage is correct, the form is stated, and the two facts simply sit in different columns of your mental arithmetic.
The general lesson transfers. When a panel names a form, look the form up; when it names none, the percentage is the only thing you have and you should know that is what you have. A label that prints “Zinc 11 mg, 100%” and nothing else is telling you less than this one, while looking identical at a glance.
The practical risk is stacking
Neither of these amounts is a problem on its own. The problem, if there is one, arrives when they are added to something else, and this is where a Daily Value percentage is at its most misleading — not because it is wrong, but because it invites you to stop after one bottle.
Zinc is in most multivitamins. It is in a great many cold remedies. It turns up in men’s formulas and in separate zinc tablets that commonly run to 15, 25 or 50 mg. Add a 25 mg zinc tablet to this capsule and you are at 36 mg, closing on the 40 mg Upper Intake Level from a cabinet rather than from any single product.
The NIH records what sustained high intakes do: doses of 50 mg or more, taken for weeks, “can interfere with copper absorption (which can cause low copper status), reduce immune function, and lower HDL cholesterol levels”. At 11 mg this product is nowhere near that. Two products and a cold remedy is a different sum.
Niacin behaves the same way. B-complexes, energy products and fortified foods all carry it, the label here does not say which form its 20 mg is, and an Upper Intake Level of 35 mg is not far away if two or three sources are running at once.
The arithmetic is simple and almost nobody does it: add the milligrams across everything you take, then compare the total with the Upper Intake Level. Not the percentages — the milligrams. Percentages from different labels are percentages of the same reference and can be added, but the milligram is the figure that means something at the end of it.
How to read a percentage on any panel
Four questions, in order, applicable to any Supplement Facts panel you pick up.
- Does the arithmetic check out? Amount divided by the FDA’s Daily Value. Two rows on this label pass. It is a low bar and it is worth checking, because a panel that gets this wrong has told you something about how carefully it was made.
- What is the Upper Intake Level? That is the number that answers “is this a lot”, and it is never printed on a label. Niacin 35 mg, zinc 40 mg, both from the NIH.
- Is the form stated? If yes, look it up: form drives absorption, and a stated form is a disclosure rather than a detail. If no, you cannot compare two products on anything but content.
- What else are you taking that contains it? The only question on this list whose answer is not on any label, and the one most likely to matter.
Run those four on this bottle and it comes out well on the first three and hands you the fourth to do yourself. Both percentages are right, both forms are stated, both Upper Intake Levels are comfortably clear, and the zinc form is the least absorbed of the common ones — which you only know because the label said so.
The larger point is about scope. Everything in this post applies to 31 mg of a 601 mg capsule. The remaining 570 mg has no Daily Values, no percentages, no individual amounts and therefore nothing to check in any of these four ways. The part of this label that can be read carefully is the part that is barely there.
Read the blend row first, then decide
Thirty capsules, one a day. Two named nutrients with percentages that both check out, and then 570 of the 601 milligrams in the capsule inside a proprietary blend with no amounts on it. The live price and the 60-day return terms are both on the seller’s checkout screen.
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