The short version
- The US Preventive Services Task Force gives folic acid an A recommendation, 400 to 800 micrograms daily for all persons planning or capable of pregnancy, reaffirmed in 2023 against an estimated 3,000 neural-tube-defect-affected pregnancies a year in the US.
- A 2024 systematic review and meta-analysis found vegan adults had significantly lower serum vitamin B12 and higher total homocysteine than omnivores, and that vegans who supplemented had better readings on every biomarker measured.
- In 3,490 US females aged 12 to 21, iron deficiency was present in 38.6% at a ferritin cutoff of 25 micrograms per litre, and 83.6% of those had no anaemia.
- In 2022 the US Preventive Services Task Force found the evidence insufficient to judge multivitamins for preventing cardiovascular disease or cancer, and recommended against beta carotene and vitamin E.
- An estimated 23,005 US emergency department visits a year and about 2,154 hospitalisations are attributed to adverse events from dietary supplements.
A reasonable way to judge a supplement company is to ask whether it has ever told you to buy less. So here is our attempt, written at the top of the category rather than buried at the bottom of a product page.
For a healthy adult who eats a reasonably varied diet, the number of supplements with evidence strong enough to justify a standing monthly charge is small. Not zero. Small. Most of what gets sold in this industry is sold against a worry rather than against a measurement, and a worry has no dose.
The situations where the evidence is genuinely on the side of supplementing
Anyone who could become pregnant. This is the strongest case in the entire category and it is not close. The US Preventive Services Task Force gives folic acid an A recommendation: 400 to 800 micrograms daily for all persons planning or capable of pregnancy. It reaffirmed that position in 2023, noting that neural tube defects affect an estimated 3,000 pregnancies a year in the US. An A grade means the Task Force found high certainty of substantial net benefit. Almost nothing else on a supplement shelf has one. What form that folic acid should take, and what else belongs in a prenatal vitamin, are separate questions worth their own answers.
People on a vegan diet. Vitamin B12 is not meaningfully available from plants. A 2024 systematic review and meta-analysis found vegan adults had significantly lower serum B12 and significantly higher total homocysteine than omnivores, which the authors read as functional B12 deficiency and not merely a low lab number. The same analysis found that vegans who supplemented had better readings across every biomarker than those who did not. This is a genuine gap that a cheap tablet closes.
Menstruating women, for iron — after a test. In a nationally representative sample of 3,490 US females aged 12 to 21, iron deficiency was present in 38.6% at a ferritin cutoff of 25 micrograms per litre, and 83.6% of those had no anaemia at all. A standard blood count misses it. But iron is the clearest example of why measuring beats guessing: it is the one common supplement where taking it when you do not need it is a bad idea.
Anyone with a documented low result, a malabsorption condition, or a genuinely restricted intake. That is a clinical conversation, not a shopping decision.
That last group is the honest use case for a broad multivitamin: one tablet covering several plausible gaps for someone whose intake is genuinely restricted, whose appetite has dropped, or whose absorption is impaired. If none of those describe you, it is the first item to skip rather than the first to buy.
Where the general case falls apart
Notice what those four have in common: a specific nutrient, a specific population, and a reason. Now compare the general case. In 2022 the Task Force reviewed vitamin, mineral and multivitamin supplementation for preventing cardiovascular disease and cancer in healthy adults and issued an insufficient-evidence statement — after decades of trials, it could not determine whether the benefits outweigh the harms. On two supplements it went further and recommended against: beta carotene, where it concluded with moderate certainty that harms outweigh benefits, and vitamin E, where it found no net benefit.
Vitamin D is the interesting middle case, and it deserves the nuance. It is worth correcting when it is low. It is also the ingredient where more stopped being the answer some years ago, and where the question of how much vitamin D you should take now has better data behind it than the question of whether to take it.
Supplements are not a free bet
The usual argument for taking something with weak evidence is that it cannot hurt. Mostly true, not always. Using nationally representative surveillance from 63 emergency departments, researchers estimated 23,005 US emergency department visits per year attributable to adverse events from dietary supplements, and about 2,154 hospitalisations. Weight-loss and energy products drove most of the cardiac presentations in young adults. Among adults 65 and over, 37.6% of supplement-related visits were choking or difficulty swallowing the pill itself — micronutrients were implicated in 83.1% of those.
None of that makes supplements dangerous as a class. It makes them a real intervention with a real, small downside, which is the correct frame for deciding whether one earns a place in your month.
Four questions to run on your own shelf
- What would tell me this is working? If you cannot name the signal — a lab value, a symptom, a training metric — you have no way to stop.
- Did anything measure that I was short? A basic panel tells you more in a morning than a year of guessing.
- Would I still take this if it cost double? A good way to find the items you are keeping out of habit. If more than a couple fail, it is worth looking hard at what to cut from your stack.
- Do I know who tested it? Third-party testing is the difference between a claim and a verified batch, and it is the one quality question worth asking of every brand, ours included.
What we'd actually tell you
Measure, then supplement the thing that was low, at the dose that matches, and retest. If you are pregnant or planning to be, folic acid is the exception that needs no test and no debate — start it and talk to your clinician about the rest. If you eat no animal products, take B12.
Everything beyond that should have to argue for itself. Including ours.
Good questions
Do I need to take any supplements if I eat well?
Probably very few. For a healthy adult eating a varied diet, the list with evidence strong enough to justify a standing monthly charge is short. The clear exceptions are folic acid for anyone who could become pregnant, B12 on a vegan diet, iron where a ferritin test shows you are low, and whatever a blood test or a clinical condition specifically identifies.
Isn't it worth taking something just in case?
Rarely, because a worry has no dose. Just-in-case supplementing means you cannot tell whether it is working and cannot tell when to stop. It also is not entirely free: an estimated 23,005 US emergency department visits a year are attributed to supplement-related adverse events. Test, treat the specific gap, retest.
Which blood tests are worth asking for before I buy anything?
Ask about vitamin D, B12, ferritin and thyroid function as a starting panel, and discuss with your clinician what makes sense for you. Ferritin is the one most often missed in menstruating women, because a standard complete blood count will look normal while iron stores are depleted. One morning of testing usually redirects more money than any article can.
You sell supplements. Why would you tell me not to buy them?
Because the alternative is selling you something you cannot evaluate, which works exactly once. We would rather have three products you can justify than eight you keep out of habit. If an item on our site does not answer the question of who it is for and what would tell you it is working, that is a fair reason not to buy it.
Is a multivitamin a reasonable safety net?
It is the most common answer and the weakest one. The US Preventive Services Task Force found the evidence insufficient to determine whether multivitamins prevent cardiovascular disease or cancer in healthy adults. A multivitamin can be sensible for someone with genuinely restricted intake, reduced appetite, or absorption problems. As general insurance against an unmeasured worry, it mostly buys reassurance.
How long should I give a supplement before deciding it does nothing?
Decide the window before you start, and make it specific to the mechanism. Something correcting a measured deficiency should be re-tested at the interval your clinician suggests, often three months. Something aimed at a symptom needs a defined trial period and an honest verdict at the end of it. An open-ended subscription with no evaluation date is a habit, not a protocol.
Sources
- US Preventive Services Task Force. Folic Acid Supplementation to Prevent Neural Tube Defects: US Preventive Services Task Force Reaffirmation Recommendation Statement. JAMA, 2023. View study
- Niklewicz A, Hannibal L, Warren M, Ahmadi KR. A systematic review and meta-analysis of functional vitamin B12 status among adult vegans. Nutr Bull, 2024. View study
- Weyand AC, Chaitoff A, Freed GL, et al. Prevalence of Iron Deficiency and Iron-Deficiency Anemia in US Females Aged 12-21 Years, 2003-2020. JAMA, 2023. View study
- US Preventive Services Task Force. Vitamin, Mineral, and Multivitamin Supplementation to Prevent Cardiovascular Disease and Cancer: US Preventive Services Task Force Recommendation Statement. JAMA, 2022. View study
- Geller AI, Shehab N, Weidle NJ, et al. Emergency Department Visits for Adverse Events Related to Dietary Supplements. N Engl J Med, 2015. View study
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
