A nutrition label is not written so you can understand it at a glance: it is written to comply with a regulation. That makes it reliable and opaque at the same time. These are the four things you need in order to read one in ten seconds.
1. The serving rules over everything else
Every figure on the panel refers to one serving, not to the package. It is the commonest mistake and the most expensive: a bag that looks like a single portion can declare two and a half servings, and then the calories you just read have to be multiplied by two and a half.
Before looking at anything else, read two lines: serving size and servings per container. If they do not match what you are about to eat, the rest of the panel does not say what you think it says.
2. The percentage refers to a person who is not you
The percent daily value is calculated against a reference diet of 2,000 kcal. It is not your diet: it is a convention so that labels can be compared with one another. If you eat 2,600 kcal, all those percentages run high for you; if you eat 1,600, they run short.
It is for comparing two products, not for planning your day.
3. The 5 and 20 rule
It is the shortcut published by the labelling authority itself, and it works without a calculator:
- 5 % or less of the daily value in a nutrient: that product is low in it.
- 20 % or more: it is high in it.
What makes it useful is applying it in both directions. You want 20 % or more in fibre, calcium, iron or potassium. You want 5 % or less in saturated fat, sodium and added sugars. With two products in your hands, that comparison takes five seconds and is right almost every time.
4. The printed figure has legal leeway
Here is what almost nobody knows. The figure on the label is not exact, and it does not have to be: the regulation allows a tolerance, and it allows it in two different directions depending on the nutrient.
- For nutrients you want to get — added vitamins and minerals, protein, fibre — the product must contain at least what is declared. It may have more.
- For those you want to limit — calories, sugars, total fat, saturated fat, sodium — the product may not exceed what is declared beyond a margin. It may have less.
In other words: the manufacturer has an incentive to declare protein on the low side and sodium on the high side, because that way it complies comfortably in both directions. The label is honest and is still giving you the scenario that suits it best.
The rounding trick
When an amount falls below a certain threshold, the regulation allows it to be declared as zero. That is why products exist that advertise «0 g trans fat» and carry partially hydrogenated oil in the ingredient list. Each serving has little; three servings no longer do.
The practical rule: when the panel says zero and the ingredient list says otherwise, the ingredient list wins.
The ingredient list, in order of weight
Ingredients are ordered from most to least by amount. That turns the list into a bar chart without bars: if sugar appears third, there is more sugar than everything that comes after it put together.
The trick to distrust is splitting the sugar: a product carrying glucose syrup, brown sugar, dextrose and juice concentrate spreads the same thing across four names, so none of them climbs to the top places. Added together they would be first.
What a claim can and cannot say
«No added sugar» does not mean no sugar: apple juice has no added sugar and is loaded with its own. «Light» may refer to the colour. «Natural» has, in practice, no definition that obliges anything.
The claims that are regulated — those linking a nutrient to a function of the body — have a public register where you can look up which were approved and, more interestingly, which were applied for and rejected. That second list is the one that really shows what is demonstrated and what is not.
Where each figure comes from
- FDA — Nutrition facts panel, the 5 and 20 rule, tolerances and rounding rules.
- ODS · NIH — Dietary reference intakes.
- European register of nutrition and health claims — approved and rejected.
United States Government agencies publish in the open and their works are not subject to copyright under 17 U.S.C. § 105. Every figure can be checked one by one; the writing of this article is our own work.
This is a summary. The detail — the fine print of the reference tables, the nineteen micronutrients with their recommendation and upper limit, and the approved claims in their official wording — needs more room. It is in the Codex of the Table, a 78-page PDF in Spanish, English and French.
Published by VILLUMINATIONS. This text is informational and does not replace the care of a licensed health professional.
