Understanding supplement labels and serving sizes

Supplement labels are regulated documents, not adverts, which is why they are the most reliable part of any pack. They are also written in a compressed style that hides the comparison you actually want. Here is how to decode one in under a minute.

Serving size comes first

Every amount on the panel refers to one serving, and a serving is not always one capsule. If product A lists 400 mg per capsule and product B lists 400 mg per two capsules, B contains half as much per capsule — and the pack will run out twice as fast.

%NRV and %DV

In the EU and UK, labels show %NRV — Nutrient Reference Value. In the US and Canada, the Supplement Facts panel shows %DV — Daily Value. Both are single reference figures that let shoppers compare products; neither is a personal recommendation, and some nutrients have no reference value, in which case the panel simply shows the amount.

Units and conversions

Micrograms (mcg or µg), milligrams (mg) and International Units (IU) all appear, sometimes on the same pack. 1000 mcg is 1 mg. For vitamin D, 1 mcg equals 40 IU. Vitamin A and vitamin E have their own conversions, which is why their labels often show both a weight and an equivalence figure.

Ingredient order and blends

Ingredients are listed by weight, heaviest first, so a botanical named on the front of the pack but appearing last in the list is present in a small amount. A 'proprietary blend' gives a total weight for several ingredients without breaking them down — legal in some markets, but it prevents you from knowing how much of each you get.

1. Serving size and servings per container.
2. Amount per serving, with %NRV or %DV where one exists.
3. The nutrient form, for example magnesium citrate rather than just magnesium.
4. Other ingredients: capsule shell, bulking agents, sweeteners, allergens.
5. Best-before date and storage instructions.

What a claim can and cannot say

Permitted wording differs between markets, and food supplements may not be presented as treating or preventing disease. If a pack or a website implies a cure, that is a warning sign about the seller rather than a feature of the product. Approved claims tend to sound modest by comparison — that is what compliance looks like.

The bottom line

Serving size, amount per serving, form, extras, date. Five lines, always in the same place, and enough to compare any two products on the shelf honestly.

This article is educational. Food supplements are not a substitute for a varied diet or medical care. Speak to a healthcare professional about your own situation.