Proprietary blends explained: what a label is allowed to hide

What a proprietary blend line actually is

A Supplement Facts panel has one job: say what is in the container, and say how much of each thing. A proprietary blend line does the first half and declines the second. It prints a blend name, a single total weight, and underneath it a list of ingredient names with no figure beside any of them.

On this bottle that line reads Proprietary Blend, 195 mg, and under it sit six botanical extracts: Grape Seed, Horse Chestnut, Motherwort, Hawthorn Berry, Gotu Kola and butcher's broom. You are told the six names, and what the six weigh together. You are not told what any single one weighs, and no arithmetic on the panel recovers it.

A blend is not an ingredient, a process or a delivery system. It is a formatting decision about disclosure. That is ordinary in this aisle, and a blend by itself is not evidence of anything. It is simply the format that removes dose from the conversation.

What the rules permit, and who checks

A boundary first. This site cites six sources and none of them is a regulation on blend formatting, so we will not quote a rule we have not opened. What follows is what the FDA publishes for consumers, plus what is printed on the bottle.

The FDA questions and answers page on dietary supplements is direct about the starting point: the agency “does not have the authority to approve dietary supplements before they are marketed”. Nobody at a federal desk signed off on this panel before it went on sale. Responsibility sits with the firm, which must have substantiation that a claim it makes is truthful and not misleading.

So the firm decides what the panel says, and nobody checks it in advance on your behalf. The same page notes that some supplements might interact with medicines or other supplements, which matters more than usual against a blend: an interaction question is a dose question.

Reading a blend total against an ingredient count

The arithmetic, in full. Six extracts share 195 mg. 195 mg divided by six is 32.5 mg, call it 33 mg. That average is the most quoted figure on any blend and the most misunderstood.

It is not a dose, and no ingredient is obliged to be near it. What it gives you is two hard bounds, and they hold whatever order the list is in. The largest of six numbers cannot sit below their mean, so the heaviest extract here is at least 32.5 mg. The smallest cannot sit above it, so the lightest is at most 32.5 mg.

Then the ceiling and the floor for a single ingredient. The ceiling is close to the whole blend: one extract could be nearly 195 mg on its own, the other five traces. The floor is close to zero. Both of those bottles print exactly this panel line.

So read a blend total against the ingredient count, never on its own: 195 mg across two ingredients is a different proposition from 195 mg across six.

A percentage of an unknown amount is still an unknown amount

Now the part that catches out careful readers, because it looks like the opposite of hidden information.

Two of the six extracts carry a printed standardisation figure. Grape seed extract is printed as greater than 95% proanthocyanidins, horse chestnut extract as greater than 20% aescin. Most labels here print none at all, so those figures are worth something. They also do not say what people read them as saying.

A standardisation figure is a concentration, not an amount. It describes the extract in the drum: of whatever weight of it went into the bottle, at least this proportion is the named compound. To turn a concentration into an amount you multiply by a weight, and the weight is what the blend line removed. A percentage of an unknown amount is still an unknown amount.

Work it through. Grape seed is printed first, so if the order is a weight order it is at least 32.5 mg, and more than 95 per cent of at least 32.5 mg is more than about 30.9 mg of proanthocyanidins. That is a floor, and the only marker floor this panel supports. Horse chestnut is printed second, and second place has no floor at all: the heaviest could be nearly the whole blend, leaving the second a trace, and 20 per cent of a trace is a smaller trace. So the aescin amount here is unknown in a way the grape seed figure is not, though both percentages sit on the same line.

One last trap: a bigger percentage is not a bigger dose. Ninety-five per cent is a purity statement about one extract, twenty per cent is about a different compound in a different plant.