If you sell a supplement, you have probably heard the phrase "structure/function claim" thrown around by your agency or your compliance lawyer.

Most brand owners nod along. Few actually know where the legal line sits.

That line decides whether your ad copy is safe or whether it turns your supplement into what the FDA calls an unapproved new drug. That is not a small distinction. It is the difference between a scroll-stopping ad and a compliance letter.

What a Structure/Function Claim Actually Is

The Dietary Supplement Health and Education Act (DSHEA) of 1994 is the law that makes most supplement marketing possible in the first place.

Under DSHEA, you are allowed to say your product affects the structure or function of the body.

Think "supports immune health," "helps maintain healthy cholesterol levels already within a normal range," or "promotes restful sleep."

You do not need FDA approval before you run that kind of claim. That is the whole appeal of the supplement category over the drug category.

But the same law draws a hard wall around disease claims, meaning any claim that your product diagnoses, treats, cures, mitigates, or prevents a specific disease.

Cross that wall, even with one word in one ad, and your product is legally being marketed as a drug. Supplements are not approved to do that.

The Disclaimer You Are Required to Use

Every structure/function claim needs the same standard disclaimer, word for word, visible wherever the claim appears.

"This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease."

This is not optional fine print. It is what legally separates your supplement claim from a drug claim in the first place.

If your landing page carries the claim but not the disclaimer, you have a gap your compliance audit will catch eventually. Better your agency catches it first.

Structure/Function vs. Disease Claim: Side by Side

Here is where most brands actually get tripped up. The wording looks almost identical, but the legal category is completely different.

Allowed Structure/Function Claim	Disease Claim (Not Allowed)
"Supports healthy joint comfort and mobility"	"Relieves arthritis pain"
"Helps maintain blood sugar levels already within a normal range"	"Lowers blood sugar" or "treats diabetes"
"Promotes calm and relaxation"	"Reduces symptoms of anxiety disorder"
"Supports a healthy heart"	"Prevents heart disease" or "lowers blood pressure"

Notice the pattern. The allowed column always talks about a normal body function staying in a healthy range. The not-allowed column always names a specific disease, disorder, or abnormal condition and claims to act on it.

The 30-Day Notification You Might Be Skipping

Here is a step most DTC marketing teams never hear about.

Under 21 CFR 101.93, the brand (not the agency) is required to notify the FDA within 30 days of first marketing a new structure/function claim on a product label.

This notification does not ask for FDA approval. It is simply a formal record that you are making the claim and that you have substantiation on file for it.

Most founders have never filed one. If you are running the same claims language across label, website, and ad copy, it is worth asking your regulatory counsel whether this notification has actually been filed for your current claims.

The FTC Layer: Why "FDA-Allowed" Isn't the Finish Line

Here is the part that trips up even brands with clean DSHEA-compliant claims.

The FTC regulates your advertising separately from how the FDA regulates your label. The FTC does not care whether your claim is a structure/function claim or a disease claim.

It cares about one thing: do you have competent and reliable scientific evidence behind the claim, before you run the ad, not after a complaint.

That means a vague "clinically studied" claim with no study attached, or a testimonial implying a disease outcome, can get flagged by the FTC even if your FDA paperwork is perfect.

We wrote a full breakdown of how this plays out specifically for creator and UGC content, since testimonials are where disease claims sneak in the most. You can read our FTC disclosure rules guide for supplement UGC for the endorsement side of this.

What Changes in 2026

This is not a static area of law. The FDA's own 2026 priority list puts, in its words, "a brighter spotlight on modernizing oversight of dietary supplements."

A few developments worth tracking if you run supplement ads this year:

1. Peptides sold "for research purposes only." Regulatory attorneys expect the FDA to take a harder look at peptides like BPC-157 marketed in a non-drug context, since the research-use label is increasingly seen as a workaround rather than a real limitation.
2. The self-affirmed GRAS pathway. A proposed rule could eliminate the ability for companies to self-affirm that a new ingredient is Generally Recognized As Safe, which would change how fast new formulations can go to market.
3. DSHEA itself under review. Industry attorneys are openly saying the 30-plus-year-old law "should be re-evaluated and updated," which signals the baseline rules of this guide could shift in the next few years, not just enforcement intensity.
4. Caffeine labeling restrictions. New rules are expected around how caffeine content gets disclosed, which matters if your formula leans on stimulant blends in its claims.

None of this means panic. It means build your claims library on the current rules now, so you are not scrambling when the rules tighten.

Red-Flag Phrases We Catch Before They Become a Problem

When we start with a new supplement client, claims review is one of the first things we do, before a single dollar goes toward media spend.

These are the phrase patterns that almost always need a rewrite:

• Any verb that implies treatment: "cures," "heals," "fixes," "reverses," paired with a named condition.
• Comparative drug language: "works like Ozempic," "natural alternative to [prescription drug]."
• Testimonials that name a diagnosis: "my doctor said my cholesterol numbers improved" reads very differently from "I feel more energetic."
• Before/after claims tied to a disease state rather than a general wellness metric.
• Missing disclaimer text on a landing page, even when the ad itself has it.

This is the exact review we walk every new client through. If you want to see the fuller checklist, our compliance audit breakdown covers what we check on that very first call, before we touch a single campaign.

Why This Matters More Than Your Ad Account

Most brands only think about claims language after an account gets flagged.

By then, you are not just rewriting copy. You are often rebuilding ad accounts from scratch, which costs weeks of lost learning data and momentum.

We have written separately about what that recovery process actually looks like, in our guide to getting a restricted Meta ad account back online. It is a far harder conversation than getting the claims right the first time.

Getting your claims library right before you scale spend is cheaper, faster, and a lot less stressful than recovering from a restriction after the fact.

How We Handle This for eBrandX Clients

This is part of why we built a compliance pass into every creative brief we run for supplement brands, not as a one-time audit, but as a standing part of how we write and approve ad copy.

Every structure/function claim in a script, headline, or caption gets checked against the disease-claim line before it ever reaches a media buyer.

If your current agency is not doing that, or if you are not sure whether they are, that is worth a direct conversation before your next big creative push.

If you want more of this kind of breakdown, plus the templates and swipe files we actually use with clients, our Supplements Scaling Insiders community covers compliance, creative, and scaling strategy in more depth than a blog post can.

Claims language is not the most exciting part of running a supplement brand. But it is the part that decides whether your best-performing ad is an asset or a liability. Get it right once, and you stop thinking about it until the rules change again.