John M. Carmack
There's no such thing as 100%
Your cereal box says "Vitamin C: 100%." A hundred percent of what? Of a number some very careful scientists picked for an average adult who is not you.
That's not a scam. It's a compromise. And once you see how it's built, the label reads differently.
The alphabet soup, decoded. All these acronyms live under one umbrella: the DRI, the Dietary Reference Intakes the US and Canada publish (Europe has its own, called DRVs; they mostly agree). The DRI isn't one number. It's a small family (NIH ODS):
- EAR — the amount that covers half of people. Useful to scientists, useless to you: aim for the EAR and it's a coin flip whether you came up short.
- RDA — the EAR plus a safety cushion, set to cover about 97–98% of healthy people. THIS is the "aim for roughly here" number. Most labels are built on it.
- AI — when the data's too thin to draw an RDA, they set an "Adequate Intake" instead: an honest best guess. A lot of nutrients are AIs, not RDAs. The science isn't finished.
- UL — the ceiling. The most you can take every day before the risk of harm starts to climb. Not a target. A guardrail.
So a nutrient isn't a number. It's a range. Picture a line: a floor on the left (go under, you're deficient), a target in the middle, a ceiling on the right. You want to live in the wide, comfortable part.
Roughly 22× headroom between the target and the ceiling. This is why nobody's ever hurt themselves with an orange (NIH ODS, Vitamin C).
Other nutrients give you far less room.
Same picture, a much tighter band — under 4× headroom (NIH ODS, Zinc). The shape of the safe range is different for every nutrient.
Not every nutrient even has a ceiling. Thiamin, riboflavin, B12, biotin, vitamin K — no UL has been set for any of them. That does NOT mean "megadose freely." It means the evidence for harm at high intakes is too thin to draw the line. Absence of a ceiling is absence of data, not a green light. (That's the kind of honesty a label has no room to print.)
Now, the label's one number. The %DV — Percent Daily Value — is a single figure the FDA picked for everyone, on a 2,000-calorie basis (the current set took effect in 2020; FDA). One number. For a pregnant 30-year-old, a sedentary 70-year-old, a teenage athlete, and you.
Take iron.
A man needs about 8 mg; a menstruating woman, 18; pregnancy, 27 — all under the same 45 mg ceiling (NIH ODS, Iron). Same label, wildly different "100%." The %DV can't tell you which one you are. It was never trying to — it's a shelf-comparison tool, not a personal target.
Here's the part where I talk you off the ledge. None of this means you should start weighing food and running spreadsheets at dinner. Eat a varied diet — actual plants, a real mix — and you land in the comfortable middle on almost everything without trying. The numbers matter at the edges: a nutrient you're genuinely low on, or a supplement you're taking by the fistful. That's it.
And I'll say the vegan part plainly, because I always do: the one number a plant-based eater should actually put on the calendar is B12. Supplement it (NIH ODS, B12). It's cheap, it's non-negotiable, and — see above — it has no ceiling to fret about. Everything else, breathe.
Why Vegify cares. Because "100% of the label" is the wrong question, and we'd rather answer the right one: are you in your range, for the nutrients that matter to you? That means storing nutrients as floors, targets, and ceilings — not single numbers — and eventually letting the range fit the actual person doing the cooking. That feature's coming. This post is the groundwork.
The label isn't lying to you. It's just answering an easier question than the one you have. :)
(Reference values from the NIH Office of Dietary Supplements; adult US DRIs. General information, not medical advice — targets shift with age, sex, pregnancy, and health.)