How to Evaluate Health Claims — A Skeptic's Toolkit

The supplement industry makes thousands of claims. Here’s how to tell which ones hold up.

Dietary supplements in the United States are regulated under the Dietary Supplement Health and Education Act (DSHEA) of 1994. Under DSHEA, supplements do not require FDA approval before marketing, and companies can make “structure/function” claims (e.g., “supports immune health”) without clinical evidence — as long as they include the standard disclaimer.

This regulatory framework means the burden of evaluation falls largely on you, the consumer. Here’s how to do it.

The evidence hierarchy

Not all studies are created equal. From strongest to weakest:

Systematic reviews and meta-analyses (e.g., Cochrane Reviews) synthesize multiple RCTs. These are the highest quality evidence for treatment effects.

Randomized controlled trials (RCTs) compare a treatment group to a placebo group with random assignment. Gold standard for individual studies.

Observational studies (cohort, case-control) show associations but cannot prove causation.

Case reports, expert opinion, and mechanistic reasoning are the weakest evidence for clinical claims.

Red flags in supplement marketing

“Clinically studied” without a citation. This phrase is nearly meaningless without knowing what was studied, by whom, at what dose, with how many participants, and whether results were statistically significant.

Animal and cell studies presented as human evidence. “Studies show…” may refer to rat models or petri dish experiments that have limited relevance to human supplementation.

Proprietary blends. If a company won’t tell you how much of each ingredient is in the product, you can’t determine whether any ingredient is present at a physiologically meaningful dose.

Single-study claims. One study — especially a small, industry-funded one — is not sufficient evidence. Replication by independent groups is essential.

Appeal to authority. A physician endorsement doesn’t substitute for peer-reviewed evidence. Physicians can be wrong, biased, or financially incentivized.

How to check claims yourself

1. Search PubMed for the specific ingredient + the claimed benefit
2. Look for human RCTs, not just animal or cell studies
3. Check who funded the research — industry funding isn’t disqualifying but is a bias indicator
4. Look at sample size — studies with fewer than 30 participants per group should be considered preliminary
5. Check whether results have been replicated by independent groups
6. Consult the NIH Office of Dietary Supplements fact sheets for balanced assessments

We publish this toolkit because we believe a company confident in its own claims should be willing to teach customers how to evaluate all claims — including ours.

References

1. U.S. Congress. Dietary Supplement Health and Education Act of 1994. Public Law 103-417. NIH ODS
2. Oxford Centre for Evidence-Based Medicine. Levels of Evidence. CEBM
3. NIH Office of Dietary Supplements. Dietary Supplement Fact Sheets. ODS