A dietary supplement can reach a U.S. shelf without its manufacturer proving, to anyone, that it works. This guide answers the most common questions about how that gap works, synthesized from the reporting in The Hollow Aisle.
Under the Dietary Supplement Health and Education Act of 1994 (DSHEA), a manufacturer can formulate a new supplement, begin production, and start selling it to the public without submitting any evidence of safety or effectiveness to the FDA beforehand — and in most cases without notifying the agency the product exists at all. A prescription drug faces the opposite presumption: unsafe and unproven until its maker demonstrates otherwise, through years of clinical trials.
Less than it appears to. The manufacturer sets what counts as a "serving," which can make a modest dose look more potent. A "proprietary blend" can legally disclose a blend's total weight without revealing how much of each individual ingredient it actually contains. And a claim like "supports immune function" requires no clinical evidence at all — only a disclaimer, printed in small type, that most shoppers never read: "This statement has not been evaluated by the Food and Drug Administration."
A disease claim — asserting a product treats, cures, or prevents a specific disease — turns a product into an unapproved drug the moment it's made, and can trigger real FDA enforcement. A structure/function claim — asserting a product "supports" a normal bodily function — requires no clinical evidence at all. Most supplement marketing copy is written to sit as close as possible to that line without crossing it.
| The claim | What a shopper often hears | What it's legally permitted to mean |
|---|---|---|
| "Supports heart health" | Reduces heart disease risk | Plays some role in cardiovascular function |
| "Supports immune function" | Fewer or milder illnesses | Involved in some aspect of immune activity |
| "Helps maintain healthy blood sugar" | Helps manage diabetes | Applies only to levels already in the normal range |
Enforcement is almost entirely reactive. A pattern typically has to emerge from adverse event reports before the FDA can act, and even then, the agency generally cannot compel a recall directly — the great majority of supplement recalls are technically voluntary, negotiated only after harm has already been documented. The FDA has used its DSHEA authority to remove an entire ingredient category from the market exactly once, in 2004, after ephedra was linked to more than 150 deaths, including a young professional athlete's.
Subscription "auto-ship" models convert a single purchase into recurring revenue. Affiliate marketers, including many health influencers, typically earn 10 to 50 percent of a referred sale — regardless of whether the product delivers any benefit to the buyer. And in multi-level marketing specifically, a 2024 federal staff report reviewing dozens of companies' own income disclosures found most participants earned $1,000 or less per year, with at least seventeen companies where most participants earned nothing at all.
"The industry's dominant business models all generate income from a sale independent of whether the product benefits the buyer."The Hollow Aisle
Unevenly. The National Academy of Sciences has recommended a minimum of 25 hours of nutrition education in medical school since 1985; national surveys have found the actual average closer to 19–24 hours, with only about a quarter to a third of schools meeting the recommended minimum. A 2014 survey found only about 14 percent of primary care physicians felt adequately prepared to counsel patients on nutrition — and supplement-specific training fares no better.
Every figure on this page is drawn from the sourced reporting in The Hollow Aisle. See the book for full citations.