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Spinal Frontiers · Wellbeing · Supplements

Supplements: what the evidence says

Which supplements are recommended, which have little evidence, and which carry risks: the official and independent sources, country by country.

25 sources · checked 6 Nov 2026

Long lists, skipped meals and night shifts make it tempting to reach for supplements. This page points you to sources that say objectively what the evidence shows: which supplements are officially recommended and for whom, which have little or no benefit, and which carry risks. We give no doses: use the official sources below, and talk to your own doctor or pharmacist, especially if you take medicines or have an operation coming up.

The common supplements at a glance

Most people get the nutrients they need from a varied, balanced diet, but some groups do benefit from specific supplements – and a few popular products carry real risks, including before surgery. Below is a two-minute guide to the supplements clinicians are asked about most, summarised from NIH, NHS, NCCIH, EFSA and Cochrane sources; it is general information, not personal advice.

Before an operation: Before any operation, patients should tell the surgical team about every supplement they take, as far in advance as possible: NCCIH notes that certain supplements may increase bleeding risk or affect the response to anaesthesia. Product labels may not match what is in the pack.

Good evidence for a specific group

Creatine

Creatine can increase strength and power for short bursts of intense effort with brief recovery, such as weight training or sprints. It has little value for endurance exercise. It is considered safe for healthy adults for several weeks or months.

Who might consider it, and cautions
Who
Healthy adults doing high-intensity strength or interval training.
Cautions
Usually causes some weight gain from water retention; rarely muscle stiffness, cramps or stomach upset. Sports supplements can be contaminated with unlabelled stimulants or steroids – third-party-tested products reduce this risk.

NIH ODS – Exercise and athletic performance (consumer)

Good evidence for a specific group

Iron

Most people get enough iron from a varied diet, but some groups are at real risk of iron deficiency anaemia. Iron supplements should be guided by a confirmed need rather than taken routinely.

Who might consider it, and cautions
Who
Women with heavy periods, pregnant women, frequent blood donors, people who avoid meat, poultry and fish, and people with cancer, gut disorders or heart failure. A GP may test and advise.
Cautions
Commonly causes constipation, nausea and stomach pain. Accidental overdose is a leading cause of fatal poisoning in young children – store safely. People with haemochromatosis should avoid iron and vitamin C supplements. Reduces the effect of levothyroxine and the absorption of levodopa; acid-reducing medicines can reduce iron absorption.

NHS – Iron · NIH ODS – Iron (consumer)

Good evidence for a specific group

Vitamin B12

Vitamin B12 is found naturally only in animal foods, so vegans need fortified foods or supplements. Absorption falls with age and with some medicines and conditions. In the UK the most common cause of deficiency is pernicious anaemia, which is usually treated with injections rather than tablets.

Who might consider it, and cautions
Who
Vegans and some vegetarians; adults over 50; people on long-term metformin or proton pump inhibitors; people after gastrectomy or weight-loss surgery; people with coeliac or Crohn's disease.
Cautions
B12 has not been shown to cause harm even at high doses, though the NHS notes there is not enough evidence on the effects of high daily doses. Suspected deficiency should be tested, not just treated, as the cause matters.

NIH ODS – Vitamin B12 (consumer) · NHS – Vitamin B12 or folate deficiency anaemia: causes

Good evidence for a specific group

Vitamin D

In the UK the NHS advises everyone to consider vitamin D in autumn and winter. With calcium it slightly increases bone strength in older adults, but it is unclear whether it prevents fractures or falls. Trials show it does not prevent cancer, heart disease, depression or type 2 diabetes.

Who might consider it, and cautions
Who
Everyone in autumn and winter (UK advice); all year for people who are rarely outdoors or housebound, live in care homes, cover most of their skin outdoors, or have dark skin; also people with conditions that limit fat absorption (e.g. Crohn's, coeliac disease) or after gastric bypass. Long indoor theatre days count as little sun exposure.
Cautions
Too much over a long period can raise calcium levels and damage the kidneys and heart; high levels almost always come from supplements, not sunlight. May interact with thiazide diuretics (calcium too high), statins (high doses), steroids such as prednisone (lower vitamin D) and orlistat. People with medical conditions should check with their doctor.

NHS – Vitamin D · NIH ODS – Vitamin D (consumer)

Mixed or limited evidence

Calcium

Some studies find calcium supplements, with or without vitamin D, raise bone density in older adults, but others do not, and it is not clear whether they prevent fractures. Studies disagree on whether supplements affect heart disease risk; experts overall think calcium intake does not.

Who might consider it, and cautions
Who
People whose diet is low in calcium, including postmenopausal women and those who avoid dairy (lactose intolerance, milk allergy, vegan diets) – ideally after discussing bone health with their doctor.
Cautions
Can cause wind, bloating and constipation. Reduces absorption of quinolone antibiotics (e.g. ciprofloxacin), levothyroxine and the HIV drug dolutegravir if taken too close together; with lithium can raise calcium levels.

NIH ODS – Calcium (consumer)

Mixed or limited evidence

Glucosamine and chondroitin

It remains uncertain whether glucosamine and chondroitin help knee osteoarthritis, and guidelines disagree: the 2019 ACR/Arthritis Foundation guideline strongly recommends against them for the knee. For the hip, evidence does not support glucosamine. Large studies found no major safety problems.

Who might consider it, and cautions
Who
People with knee osteoarthritis who wish to try them, after discussing the conflicting evidence with their doctor.
Cautions
Associated with an increased risk of bleeding in people taking warfarin – relevant before surgery. Little is known about safety in pregnancy and breastfeeding.

NCCIH – Glucosamine and chondroitin for osteoarthritis

Mixed or limited evidence

Magnesium

Supplements may lower blood pressure by only a small amount and modestly reduce migraine frequency in small studies. Whether they help diabetes or osteoporosis is not yet known. The NIH fact sheet does not cover sleep, and cramps are listed only as a sign of severe deficiency.

Who might consider it, and cautions
Who
People at risk of low magnesium: older adults, people with Crohn's or coeliac disease, type 2 diabetes or long-term alcohol misuse, and long-term users of acid-reflux medicines. Migraine use only under a clinician's care.
Cautions
Too much from supplements causes diarrhoea, nausea and cramping; extremely high intakes can cause irregular heartbeat. Reduces absorption of bisphosphonates and some antibiotics if taken too close together. Diuretics and long-term acid-reducing medicines can alter magnesium levels.

NIH ODS – Magnesium (consumer)

Mixed or limited evidence

Melatonin

Melatonin may help jet lag, especially after eastward flights. Studies in shift workers were small or inconclusive, and there is not enough strong evidence to recommend it for chronic insomnia, where cognitive behavioural therapy (CBT-I) is the first-line treatment. In the UK, the NHS says most adults aged 55 or over can take it for short-term sleep problems, and younger adults if a specialist recommends it.

Who might consider it, and cautions
Who
Travellers with jet lag; adults over 55 with short-term sleep problems, via their doctor; younger adults only on specialist advice.
Cautions
Short-term use appears safe for most people; long-term safety is unknown. Side effects include headache, dizziness, nausea and daytime sleepiness, especially in older adults. People taking blood thinners or with epilepsy need medical supervision; tell the doctor about liver or kidney problems or autoimmune conditions. Many products do not contain the amount stated on the label.

NCCIH – Melatonin: what you need to know · NHS – Who can and cannot take melatonin

Mixed or limited evidence

Omega-3 / fish oil

Eating oily fish is linked to heart health, and omega-3s lower triglycerides. In large trials of people without heart disease (VITAL, ASCEND), supplements did not reduce major cardiovascular events overall. The American Heart Association does not recommend them for people who are not at high cardiovascular risk.

Who might consider it, and cautions
Who
People with heart disease or high triglycerides, under their doctor's guidance; oily fish is the preferred source.
Cautions
High doses have antiplatelet effects and may prolong clotting with warfarin – INR should be monitored; relevant to perioperative bleeding planning. High-dose omega-3 slightly increased atrial fibrillation risk in people with or at high risk of heart disease. Side effects are usually mild (fishy taste, heartburn, nausea, diarrhoea).

NIH ODS – Omega-3 (consumer) · NIH ODS – Omega-3 (health professional)

Mixed or limited evidence

Probiotics

Probiotics taken with antibiotics may reduce antibiotic-associated diarrhoea and, with moderate certainty, C. difficile diarrhoea; the best strains and duration are unclear. Evidence for IBS is suggestive but not definite, and no benefit was found for Crohn's disease or urinary infections. Effects are strain-specific, so results for one product do not apply to another.

Who might consider it, and cautions
Who
People taking antibiotics who want to reduce the risk of diarrhoea, after discussion with their doctor or pharmacist.
Cautions
Generally safe in healthy people, but severe or fatal infections have been reported in premature infants; seriously ill or immunocompromised patients need caution and monitoring. Some products contain organisms not listed on the label.

NCCIH – Probiotics: usefulness and safety

Mixed or limited evidence

Zinc and vitamin C for colds

Regular vitamin C does not reduce the number of colds in the general population, though it may slightly shorten them; starting it once symptoms appear shows no consistent benefit. People under short periods of extreme physical stress had about half the cold risk. Zinc lozenges or syrup started early may speed recovery but do not seem to reduce symptom severity.

Who might consider it, and cautions
Who
People under heavy physical stress (for vitamin C); otherwise routine use is not justified according to the Cochrane review.
Cautions
Too much vitamin C causes diarrhoea and stomach cramps and may worsen iron overload in haemochromatosis; it may interact with chemotherapy and radiotherapy. Long-term excess zinc can cause copper deficiency; zinc reduces absorption of quinolone and tetracycline antibiotics and penicillamine.

Cochrane – Vitamin C for preventing and treating the common cold (2013) · NIH ODS – Zinc (consumer)

Little evidence of benefit

Collagen

There is no NIH or NHS fact sheet on collagen supplements. EFSA assessed the claim that collagen hydrolysate helps maintain joints and concluded that a cause-and-effect relationship has not been established.

Who might consider it, and cautions
Who
No group identified by these sources; anyone considering it for joint symptoms should discuss evidence-based options with their doctor.
Cautions
No safety data are summarised by these official sources; general supplement quality and labelling concerns apply.

EFSA – Opinion on collagen hydrolysate and maintenance of joints

Little evidence of benefit

Multivitamins

Most studies find multivitamin-mineral supplements have little or no effect on heart disease, cancer or other chronic diseases in the general population. Specific groups can benefit, notably before and during pregnancy (folic acid) and people with restricted diets.

Who might consider it, and cautions
Who
People planning pregnancy or pregnant (a prenatal product); vegetarians and vegans; people with poor appetite or very low-calorie diets; adults over 50 who may need vitamin B12 from supplements or fortified foods.
Cautions
Combined with fortified foods and other supplements, intake can exceed safe limits for iron, vitamin A, zinc and folic acid. Smokers (and perhaps former smokers) should avoid products with large amounts of beta-carotene or vitamin A; excess vitamin A in pregnancy may cause birth defects. Anyone on warfarin should check before taking any product with vitamin K.

NIH ODS – Multivitamin/mineral supplements (consumer)

Little evidence of benefit

Protein powders / whey

Protein supports muscle building and repair, but most active people can meet their needs from food. High protein intakes seem safe, yet there is no benefit to taking more than recommended amounts. Powders are a convenience, not a necessity.

Who might consider it, and cautions
Who
People whose diet genuinely falls short of their protein needs, for example with low appetite or very restricted diets.
Cautions
As with all sports supplements, some products have been found to contain unlabelled stimulants, steroids or hormone-like ingredients; look for independent third-party testing.

NIH ODS – Exercise and athletic performance (consumer)

Caution: interactions or risks

Ashwagandha

Small studies of six to eight weeks suggest ashwagandha extracts might reduce stress and anxiety and slightly improve sleep, but products and doses varied and more research is needed. Safety beyond about three months is unclear, and rare cases of liver injury have been reported.

Who might consider it, and cautions
Who
No group with established benefit; anyone considering it, especially if on medicines, should talk to their doctor first.
Cautions
Not recommended for people about to have surgery, or for those with autoimmune or thyroid disorders. Avoid in pregnancy and breastfeeding; may not be safe with prostate cancer. May interact with medicines for diabetes, blood pressure, thyroid and seizures, sedatives and immunosuppressants.

NCCIH – Ashwagandha · NIH ODS – Ashwagandha (consumer)

Caution: interactions or risks

Caffeine (tablets, powders, energy products)

Caffeine may help endurance and team-sport performance but not short maximal efforts, and people vary in how they respond. EFSA considers moderate single doses and moderate daily totals from all sources safe for healthy adults, with lower limits in pregnancy and breastfeeding. Concentrated products make it easy to exceed these totals without noticing.

Who might consider it, and cautions
Who
Healthy adults who already know how they tolerate caffeine; coffee and tea count towards the daily total.
Cautions
High intakes disrupt sleep and can cause irritability and anxiety – relevant before night shifts and after on-call. Very large single doses can be fatal. Pregnant and breastfeeding women have a lower safe limit; teenagers should keep intake low.

EFSA – Caffeine · NIH ODS – Exercise and athletic performance (consumer)

Caution: interactions or risks

Turmeric / curcumin

NCCIH says there is not enough evidence to conclude that turmeric or curcumin helps any health condition. Early evidence for knee osteoarthritis pain is positive but needs higher-quality trials. Cases of liver injury have been reported, particularly with 'high-bioavailability' formulations.

Who might consider it, and cautions
Who
No group with established benefit; people with osteoarthritis curious about it should discuss it with their doctor.
Cautions
Can cause nausea, reflux, diarrhoea or constipation. Stop and seek medical advice if signs of liver injury appear (fatigue, nausea, dark urine, jaundice). May be unsafe in pregnancy. Herbs can interact with medicines, so check with a doctor or pharmacist first.

NCCIH – Turmeric

Check any supplement yourself

Official guidance and reference sources

For readers who want the regulations and the formal guidance behind the summaries above.

What the official bodies agree on

  • Most people should get the nutrients they need from a varied and balanced diet; only some people need supplements. NHS: 'Most people should get all the nutrients they need by having a varied and balanced diet.' (NHS, source)
  • In the UK, everyone is advised to consider vitamin D in autumn and winter, and certain groups (for example people rarely outdoors, people who cover most of their skin, people with dark skin) all year round. (NHS, source)
  • Supplements are not an equivalent replacement for a varied diet and are usually unnecessary for healthy people who eat a balanced diet. BfR: 'Nahrungsergänzungsmittel sind dafür kein gleichwertiger Ersatz'; DGE: a poor diet cannot be offset by supplements. (BfR; DGE, source)
  • In Germany, people who already have adequate vitamin D status gain no additional benefit from supplements, so a general recommendation for the healthy population is not justified; supplements may make sense for risk groups, especially in winter. (BfR (December 2025), source)
  • Supplements are foods, not medicines, and are not intended to prevent or treat disease; they undergo no pre-market safety check and can carry risks including contamination and interactions. BLV: 'Nahrungsergänzungsmittel sind Lebensmittel, keine Heilmittel.' (BLV/FSVO (Switzerland); AGES (Austria), source)
  • USPSTF: evidence is insufficient to assess benefits and harms of multivitamins and most single or paired nutrients for preventing cardiovascular disease or cancer; it recommends against beta-carotene and vitamin E supplements for this purpose. (USPSTF (2022), source)
  • Tell your doctor and pharmacist what you take, including before surgery: some supplements interact with medicines. 'St. John's wort can interact in dangerous, sometimes life-threatening ways with a variety of medicines'; vitamin K can reduce the effect of warfarin; biotin can distort lab results such as troponin and thyroid tests. (NCCIH; NIH ODS; Verbraucherzentrale, source)
  • 'Natural' does not always mean safe, and some products sold as supplements (particularly for weight loss, sexual enhancement and bodybuilding) have contained undeclared prescription drugs. Report suspected side effects (UK: MHRA Yellow Card). (NCCIH; MHRA, source)

Eating well on a busy rota matters more than any pill: see Health & Nutrition for quick meals, and Body & Mind for sleep and exercise.

United KingdomOfficial advice

Vitamins and minerals

NHS (England)

Plain-English overview of each vitamin and mineral, food sources, and the risks of taking too much, starting from the position that most people can get what they need from a varied diet.

Cost
free
Language
English

Note: Pages show 'last reviewed' August 2020 with review overdue; UK-focused.

Open the source →Source checked

United KingdomOfficial advice

Vitamin D

NHS (England)

States who in the UK should consider vitamin D in autumn and winter and which groups are advised to take it all year round.

Cost
free
Language
English

Note: UK advice reflects UK latitude and sunlight; page last reviewed August 2020.

Open the source →Source checked

GermanyOfficial advice

Fragen und Antworten zu Nahrungsergänzungsmitteln

Bundesinstitut für Risikobewertung (BfR)

Federal risk assessor's Q&A on when supplements are unnecessary, which groups may benefit, and why supplements are not a substitute for a varied diet.

Cost
free
Language
German

Note: German only; dated December 2018.

Open the source →Source checked

GermanyOfficial advice

Ausgewählte Fragen und Antworten zu Vitamin D

Bundesinstitut für Risikobewertung (BfR)

Current German position on vitamin D: little added benefit for people who are already well supplied, which risk groups may benefit, and the risks of high-dose products.

Cost
free
Language
German

Note: German only; contains numeric reference values, which Spinal Frontiers should not reproduce.

Open the source →Source checked

GermanyOfficial advice

FAQ Nahrungsergänzungsmittel

Deutsche Gesellschaft für Ernährung (DGE)

The German nutrition society's view that healthy people on a balanced diet generally do not need supplements, with the specific situations where it does recommend them.

Cost
free
Language
German

Note: German only; DGE is a scientific society (publicly funded) rather than a government body.

Open the source →Source checked

SwitzerlandOfficial advice

Food supplements (Nahrungsergänzungsmittel)

Federal Food Safety and Veterinary Office (BLV/FSVO/OSAV/USAV)

Swiss regulator's explanation that supplements are foods not medicines, that healthy people rarely need them, and what the risks are (no pre-market safety check, contaminants, interactions, dubious online sellers).

Cost
free
Language
German, French, Italian, English

Note: Switzerland does not require supplements to be notified to the authorities; control relies on self-checks by manufacturers and sellers plus cantonal spot checks (page last modified June 2025).

Open the source →Source checked

AustriaOfficial advice

Nahrungsergänzungsmittel

Österreichische Agentur für Gesundheit und Ernährungssicherheit (AGES)

Austrian food-safety agency's view that supplements are unnecessary for the healthy general population, with official sampling results showing labelling and safety problems and advice on buying online.

Cost
free
Language
German

Note: German only; no date shown (sampling data to 2022).

Open the source →Source checked

European UnionOfficial advice

Dietary reference values (DRVs)

European Food Safety Authority (EFSA)

EFSA's scientific reference values for nutrients, including tolerable upper intake levels, with an interactive DRV Finder for health professionals.

Cost
free
Language
English

Note: Population reference values, not personal recommendations; contains numbers that Spinal Frontiers should not reproduce.

Open the source →Source checked

United StatesOfficial advice

Vitamin, mineral and multivitamin supplementation to prevent cardiovascular disease and cancer

US Preventive Services Task Force (USPSTF)

Graded recommendation on whether supplements prevent cardiovascular disease and cancer in healthy adults: insufficient evidence for most, recommendation against beta-carotene and vitamin E.

Cost
free
Language
English

Note: US-focused; final statement June 2022; applies to community-dwelling, non-pregnant adults only.

Open the source →Source checked

United KingdomEvidence summaries

SACN vitamin D and health report

Scientific Advisory Committee on Nutrition (SACN), UK Government

The full scientific review behind current UK vitamin D advice, for readers who want the evidence base rather than the headline.

Cost
free
Language
English

Note: Technical report (2016, page updated 2023); concerns musculoskeletal health, not general disease prevention.

Open the source →Source checked

InternationalEvidence summaries

Examine

Examine.com

Independent summaries of supplement research graded by outcome; states it is not affiliated with any supplement or food company, sells only information, and accepts no advertising or sponsorship.

Cost
freemium: much free content; Examine+ subscription for full database, guides and research feed
Language
English

Note: Commercial (subscription) business, not a public body; paid guides include dosing, which Spinal Frontiers should not reproduce.

Open the source →Source checked

United StatesEvidence summaries

Vitamins and Minerals (The Nutrition Source)

Harvard T.H. Chan School of Public Health

Academic, readable overview of what a good diet provides and where supplements may fill gaps.

Cost
free
Language
English

Note: US-focused; somewhat more open to multivitamins as a 'gap filler' than European bodies.

Open the source →Source checked

European UnionDatabases

EU Register of nutrition and health claims

European Commission (claims assessed by EFSA)

Lets readers check whether a health claim on a supplement label is authorised in the EU, and why many claims were rejected.

Cost
free
Language
English, other EU languages (about page)

Note: An authorised claim means a specific wording is permitted, not that a product is needed; search tool at https://ec.europa.eu/food/food-feed-portal/screen/health-claims/eu-register is a JavaScript app (not content-verified). Since Brexit the UK keeps its own GB register.

Open the source →Source checked

United StatesDatabases

Dietary Supplement Fact Sheets

NIH Office of Dietary Supplements (ODS)

Detailed, referenced fact sheets on individual vitamins, minerals and botanicals, in separate consumer and health-professional versions, including known medicine interactions.

Cost
free
Language
English, Spanish (many sheets)

Note: US-focused; reference values are US ones and differ from UK/EU/DACH values.

Open the source →Source checked

United StatesDatabases

About Herbs, Botanicals & Other Products

Memorial Sloan Kettering Cancer Center (MSK)

Evidence-based entries on herbs and supplements covering proven uses, adverse effects and herb-drug interactions, for patients and clinicians; also available as an app.

Cost
free (no cost stated; no login seen)
Language
English

Note: Cancer-centre perspective

Open the source →Source checked

United KingdomSafety & quality

MHRA safety alerts on products sold as food supplements

Medicines and Healthcare products Regulatory Agency (MHRA)

Example of a UK regulator alert (August 2025) on a supplement found to contain an undeclared prescription-only medicine, with how to report side effects via the Yellow Card scheme.

Cost
free
Language
English

Note: A single alert naming a specific product; better presented as an example, alongside the Yellow Card reporting site (https://yellowcard.mhra.gov.uk), which the alert names for reporting side effects.

Open the source →Source checked

United KingdomSafety & quality

Informed Sport

LGC Group

Batch-testing certification scheme for sports supplements against banned substances.

Cost
free to search (certification paid by brands)
Language
English

Note: Commercial certification scheme, not an endorsement; site does not state that residual risk remains; old URL informed-sport.com now redirects here; says nothing about efficacy.

Open the source →Source checked

GermanySafety & quality

Health assessment of food supplements

Bundesinstitut für Risikobewertung (BfR)

English explanation of how supplements are regulated in Germany (no pre-market registration, no binding maximum levels yet) and the BfR's role in assessing their safety.

Cost
free
Language
English, German

Note: Regulatory overview rather than advice on individual supplements; no date shown.

Open the source →Source checked

GermanySafety & quality

Klartext Nahrungsergänzung

Verbraucherzentralen (German consumer advice centres)

Independent consumer site that checks advertised supplement claims and lists current warnings and recalls; includes a clear page on supplement-medicine interactions and effects on lab tests.

Cost
free
Language
German

Note: German only; consumer organisation, not a regulator. Interactions page: https://www.verbraucherzentrale.de/wissen/lebensmittel/nahrungsergaenzungsmittel/wechselwirkungen-mit-medikamenten-10595 (updated February 2026).

Open the source →Source checked

GermanySafety & quality

Kölner Liste (Cologne List)

Kölner Liste (operated by HEIMSPIELE GmbH & Co. KG; partners include NADA)

Database of supplement products tested for doping substances; useful for anyone subject to anti-doping rules.

Cost
free to search (testing paid by manufacturers)
Language
German, English, Spanish

Note: Certification scheme, not an endorsement: states it is 'keine Empfehlung' to use any supplement; testing reduces but cannot exclude contamination risk; says nothing about efficacy.

Open the source →Source checked

European UnionSafety & quality

Caffeine

European Food Safety Authority (EFSA)

EFSA's risk assessment of caffeine from all sources including supplements and energy drinks, including effects on sleep: directly relevant to shift and night workers.

Cost
free
Language
English

Note: Based on a 2015 opinion; excludes people with medical conditions or on medicines; contains numeric intake levels.

Open the source →Source checked

United StatesSafety & quality

Dietary Supplements: What You Need to Know

NIH Office of Dietary Supplements (ODS)

Short primer on benefits, risks and interactions (e.g. vitamin K and warfarin, St John's wort) and on telling every clinician what you take.

Cost
free
Language
English, Spanish

Note: US regulatory context; updated January 2023.

Open the source →Source checked

United StatesSafety & quality

Using Dietary Supplements Wisely

National Center for Complementary and Integrative Health (NCCIH, NIH)

Concise safety guidance: interactions, risks around surgery and anaesthesia, 'natural' not meaning safe, and products found to contain undeclared drugs.

Cost
free
Language
English, Spanish

Note: US-focused; last updated January 2019. Related herb pages (e.g. St John's wort, updated May 2025) are more current.

Open the source →Source checked

United StatesSafety & quality

Dietary Supplements (FDA)

US Food and Drug Administration (FDA)

Explains that manufacturers, not the FDA, are responsible for checking a supplement's safety and labelling before sale, with the FDA acting only once products are on the market; links to recalls and safety alerts and to an FDA directory of selected supplement ingredients.

Cost
free
Language
English

Note: US regulator

Open the source →Source checked

How we compile this page

The summaries at the top were written from the NIH Office of Dietary Supplements, the NHS, NCCIH, EFSA and Cochrane, and reviewed from two angles: a busy surgeon's and a dietitian's. They are evidence summaries, not personal advice.

We list public-health bodies, regulators and independent evidence summaries, and two product-testing schemes for readers who are tested for doping or want third-party checks on contamination. A testing scheme is not an endorsement, and no list is complete. We do not recommend brands or products, take no money from supplement makers, and give no doses. Popular consumer guides that are tied to a supplement brand, or that give no references, are not listed. Each source was opened on 6 Nov 2026. This page is general information, not medical advice.

Not included or not yet confirmed:

  • The FDA database of tainted products sold as supplements and the EU health-claims register are linked from the official hub pages listed above.
  • We found no official guidance on nutrition or supplements for night and shift workers.
  • Some official pages, such as the NHS vitamins pages, were last reviewed several years ago; their advice is still current policy.
  • Pages that give doses or reference values are linked as sources; we do not reproduce the figures.
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