What is a dietary supplement?

A dietary supplement is a product intended to supplement the diet, containing one or more dietary ingredients — vitamins, minerals, herbs or botanicals, amino acids, enzymes, probiotics or other substances. Supplements come in various forms: pills, capsules, gummies, powders, liquids. In most countries they are regulated as food, not as medicines — meaning they do not have to prove efficacy or safety before going on sale.

Which supplements have the strongest evidence?

Supplements with robust clinical trial evidence for specific conditions include: folate (folic acid) for reducing neural tube defects in pregnancy; iron for iron-deficiency anaemia; vitamin D for deficiency prevention (particularly in those with limited sun exposure); vitamin B12 for deficiency (especially in vegans and older adults); omega-3 fatty acids for reducing triglycerides and cardiovascular risk; and iodine for preventing goitre in deficient populations. The evidence base for most other supplements is considerably weaker.

Are supplements regulated?

Regulation varies enormously by country. In the US, dietary supplements are regulated under the Dietary Supplement Health and Education Act (DSHEA, 1994) as a category of food — manufacturers do not need to prove efficacy or safety before sale. The EU (Food Supplements Directive 2002/46/EC) requires notification and sets maximum permitted levels for vitamins and minerals, but does not require efficacy proof. Australia (TGA), Japan and Canada have stricter evidence requirements for therapeutic claims. WHO's Guidelines on Food Supplements provide a harmonisation framework.

Can supplements be harmful?

Yes — supplements can cause direct harm and interact with medicines. Serious risks include: liver damage from herbal supplements (kava, black cohosh, pyrrolizidine alkaloids); vitamin toxicity at high doses (vitamin A, vitamin D, iron, selenium); stimulant effects and cardiovascular toxicity from ephedra-containing products (now banned in many countries); contamination with heavy metals (particularly in Ayurvedic and traditional Chinese medicine products); and adulteration with undeclared pharmaceutical substances (sildenafil in "herbal" sexual enhancement products, stimulants in weight-loss supplements).

What are drug-supplement interactions?

Supplements can interact significantly with prescription medicines. Clinically important interactions include: St John's Wort (Hypericum perforatum) induces cytochrome P450 enzymes, reducing plasma concentrations of antiretrovirals, ciclosporin, oral contraceptives and warfarin; high-dose omega-3 and vitamin E increase bleeding risk in patients on anticoagulants; ginkgo and ginseng affect platelet function; magnesium and calcium reduce absorption of certain antibiotics (quinolones, tetracyclines); and high-dose vitamin C may affect certain cancer chemotherapy regimens. Patients should always inform their healthcare provider of supplement use.

What is the GMJ Supplement Desk and Citation Guard?

The GMJ Supplement Desk on news.gmj.ge is a daily evidence-based reporting service covering dietary supplements, nutraceuticals and functional foods. It covers 63 ingredients across 7 formats. Uniquely, the GMJ Supplement Desk operates under a Citation Guard requirement: every article must contain a minimum of 6 verified PubMed citations before publication. This ensures that all supplement claims are traceable to peer-reviewed evidence — a standard not required of supplement manufacturers themselves and rare in journalism.

What is the GMJ SupplementIndex?

SupplementIndex (supplement.ge) is the GMJ's standalone evidence database for dietary supplements — currently covering 385 ingredients in 55 data fields. It draws on NIH DSLD (67,000+ products), the GSRS (615 substances) and EFSA opinions. Each ingredient entry includes evidence summary, dosage guidance, safety/toxicology, drug interactions, labelling information and verified product cross-references. It operates under Creative Commons BY 4.0 as a public-good resource — freely available to consumers, pharmacists and clinicians.

What is the difference between a supplement and a medicine?

The key regulatory distinction is the standard of evidence required before sale. A medicine (pharmaceutical drug) must demonstrate safety and efficacy through clinical trials before regulatory approval; manufacturers bear the burden of proof. A supplement (in most countries) only needs to demonstrate that it is safe and that label claims do not constitute disease treatment claims — no efficacy proof is required. This regulatory asymmetry allows supplements to be marketed with implied health benefits that have not been rigorously tested.

What supplement labelling problems have been found?

Independent laboratory testing of supplement products consistently reveals problems: products containing less active ingredient than stated (up to 80% in some botanical surveys); products containing ingredients not listed on the label; contamination with heavy metals (lead, arsenic, mercury — particularly in Ayurvedic and traditional Chinese medicine products); adulteration with undisclosed pharmaceutical substances (found commonly in sexual enhancement, weight-loss and sports performance supplements); and microbiological contamination. The USP, NSF International and ConsumerLab provide third-party quality verification programmes in the US.

What is the evidence for vitamin D supplementation?

Vitamin D deficiency — defined as serum 25-hydroxyvitamin D below 50 nmol/L — is prevalent globally, particularly in populations with limited sun exposure. Supplementation clearly corrects deficiency and prevents osteomalacia (bone softening) and rickets. Evidence for other claimed benefits (cancer prevention, cardiovascular protection, immune function) is more mixed: large randomised trials (VITAL, D-HEALTH, ViDA) have not consistently demonstrated benefits in people who are not deficient. Current consensus is to supplement in deficiency or high-risk populations (elderly, housebound, dark-skinned people in low-sun climates, veiled women) but to avoid high-dose supplementation in people who are not deficient.

What is melatonin and does it work for sleep?

Melatonin is a hormone produced by the pineal gland that regulates the sleep-wake cycle. As a supplement, it has moderate evidence for reducing sleep onset latency (time to fall asleep), particularly in: jet lag (timing of administration matters); circadian rhythm disorders; and in older adults with reduced endogenous melatonin production. Evidence is weaker for general insomnia in otherwise healthy adults. Unlike most supplements, melatonin has clear pharmacological activity. Doses used in studies range from 0.5mg to 5mg; high doses (10mg) sold commercially exceed physiological levels and are not more effective.

How does GMJ News cover supplements?

The GMJ Supplement Desk produces daily evidence-based coverage of dietary supplements, operating under a strict Citation Guard requirement of 6+ verified PubMed citations per article. Coverage spans 63 ingredients in seven format types. The GMJ SupplementIndex (supplement.ge) provides the comprehensive ingredient evidence database. This places GMJ among the most rigorously evidence-based supplement information sources globally — in contrast to the largely unregulated commercial supplement information landscape.

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Supplements & Nutraceuticals

GMJ News knowledge hub · last reviewed September 2026 · Georgian Medical Journal

Summary Statistics Glossary GMJ news FAQ Documents Organizations Research

More than half of adults in high-income countries take dietary supplements, feeding a global market well above 150 billion US dollars a year — yet under frameworks like the US DSHEA (1994), supplements reach the market without pre-approval of safety or efficacy, and quality, dosing accuracy and interactions with medicines remain the consumer blind spots documented by the NIH Office of Dietary Supplements and EFSA. GMJ News covers this field with original, evidence-graded journalism generated from our own structured databases: browse the Ingredients A-Z evidence profiles and the full SupplementIndex — dosage, safety, interactions and label literacy, referenced to NIH ODS, EFSA and Cochrane.

Key messages

Massive and mostly unregulated market

The global dietary supplement market exceeded $170 billion in 2023 and is growing rapidly — yet in most jurisdictions, supplements require no proof of efficacy before sale and face only post-market safety regulation.

Evidence varies enormously

A handful of supplements have strong evidence — vitamin D in deficiency, folate in pregnancy, iron for anaemia, omega-3s for cardiovascular risk — but the majority lack robust clinical trial evidence for their marketed claims.

Labelling and quality problems

Independent testing repeatedly finds that supplement products do not match their labels: some contain less active ingredient than claimed; others contain unlisted substances including prescription drugs; and botanical supplements may be adulterated or contaminated.

Citation Guard standard

GMJ News Supplement Desk articles require a minimum of 6 PubMed-verified citations per article. This Citation Guard standard ensures that every claim published on the Supplement Desk is traceable to peer-reviewed evidence — a standard not required by supplement manufacturers themselves.

Drug-supplement interactions

Supplements can interact with prescription medicines, sometimes with serious consequences: St John's Wort reduces the efficacy of antiretrovirals, warfarin and oral contraceptives; high-dose vitamin E increases bleeding risk; ginkgo and ginseng affect anticoagulation.

Regulation varies by country

In the US, supplements are regulated as food under DSHEA (1994) — not as medicines. The EU, Japan and Australia have stricter frameworks. WHO's Guidelines on Food Supplements provide a harmonisation framework, but enforcement varies enormously.

Key statistics

$170B+

global supplement market 2023

Grand View Research 2024

>50%

of adults in high-income countries use supplements

NHANES/EFSA

77K+

products in the DSLD (US database)

NIH DSLD

No pre-market

efficacy proof required in most countries

DSHEA 1994 (US)

PubMed citations required per GMJ Supplement Desk article

GMJ Citation Guard

385

ingredients in GMJ Supplement Index (supplement.ge)

SupplementIndex v10

Global dietary supplement market size (USD billions) 2019-2027 — market research estimate

Source: Grand View Research market estimates. High growth driven by wellness trends, ageing populations and COVID-19 effects.

Glossary of key terms

Dietary supplement
FDA/DSHEAA product intended to supplement the diet containing a dietary ingredient — vitamins, minerals, herbs, amino acids, enzymes, probiotics or other botanicals. Regulated as food in the US (DSHEA 1994), not as medicines.

DSHEA
FDADietary Supplement Health and Education Act (1994) — the US regulatory framework. Shifts the burden of proof from manufacturers (who do not need to prove efficacy before sale) to the FDA (who must prove a product is unsafe to remove it). Widely criticised for insufficient consumer protection.

Randomised controlled trial (RCT)
Cochrane/WHOThe gold standard for evaluating supplement efficacy — randomly allocating participants to the supplement or a placebo and comparing outcomes. Observational data (correlations) are insufficient because of confounding: healthy people tend both to take supplements and to have healthier lifestyles.

PubMed
NLM/NIHThe US National Library of Medicine's biomedical literature database — containing over 35 million citations. PubMed PMID (PubMed Identifier) is the universal citation reference for peer-reviewed biomedical publications. All GMJ Supplement Desk articles require verified PubMed citations.

DSLD
NIHDietary Supplement Label Database — a US NIH database of over 77,000 supplement products with label information. The basis for the GMJ SupplementIndex database of 385 ingredients.

Pharmacovigilance
WHO/EMAThe science and activities relating to the detection, assessment, understanding and prevention of adverse effects or any other medicine or supplement-related problem. Supplement pharmacovigilance is severely underdeveloped globally.