Supplement labels carry phrases such as supports immune function or helps maintain healthy joints. Those wordings are legally specific, and their permitted scope explains why they sound the way they do.
The claim category was created by statute
Federal law distinguishes claims about treating or preventing disease, which require the product to be a drug, from claims about affecting the structure or function of the body.
The second category was opened to supplements by legislation, allowing manufacturers to describe an effect on a normal body process without seeking prior approval for the claim.
The manufacturer must notify the regulator that the claim is being used and must hold substantiation, but the claim itself is not reviewed or authorized before it appears.
The line is drawn at disease
A claim crosses into drug territory when it names a disease, implies treatment of one, or describes a symptom characteristic of a specific condition.
Supports cardiovascular health sits on one side of the line. Lowers cholesterol names an established disease marker and sits on the other, which is why the first phrasing is ubiquitous.
Implication counts as well as wording, so imagery, product names and accompanying material can turn an otherwise permissible claim into a disease claim.
The mandatory disclaimer is part of the bargain
Any label carrying a structure-function claim must also carry a statement that the claim has not been evaluated by the regulator and that the product is not intended to diagnose, treat, cure or prevent disease.
The disclaimer exists precisely because the claim was never reviewed. It is the mechanism by which the absence of evaluation is disclosed to the buyer.
Because it appears on essentially every product in the category, it has largely stopped functioning as a signal, which is a predictable consequence of a universal warning.
Substantiation is held rather than submitted
The requirement is that a claim be truthful and not misleading and that the manufacturer possess adequate substantiation, but that evidence is not filed for review beforehand.
Enforcement is therefore reactive, arriving after a product is on the market, through warning letters or action by the agency handling advertising rather than labeling.
The quality of substantiation consequently varies enormously between a company holding controlled human trials and one relying on a mechanistic argument about an ingredient class.
What a reader can take from the wording
The presence of a structure-function claim indicates a legal category, not a level of evidence. It tells a reader what the manufacturer is permitted to say, not what the product does.
Anyone considering a supplement while taking prescription medication, managing a diagnosed condition, or during pregnancy needs a pharmacist or physician involved, because interaction and appropriateness are clinical questions the label cannot answer.