"Expensive urine" is the most durable criticism ever levelled at multivitamins. It dates from a 2007 television segment, it is repeated constantly, and for years it was a fair reading of the science.
The evidence has moved since then. Randomised trial data now exists on memory, on eye health, and — as of a 2026 conference presentation — on how the heart affects daily life. None of it turns a multivitamin into a miracle, and some of it confirms that badly designed products are worse than useless. But the blanket dismissal no longer matches the literature.
This article works through the evidence question by question: what the official reviewers say, why urine turns yellow, which nutrients are genuinely risky at high doses, and what the recent trials actually showed.
Table of Contents
- Are Multivitamins Really "Expensive Urine"?
- Why Does A Multivitamin Turn Urine Bright Yellow?
- Which Vitamins Are Risky At High Doses?
- Is High-Dose Vitamin B6 Dangerous?
- Can A Multivitamin Support Eye Health?
- Do Multivitamins Improve Memory?
- Does Omega-3 Status Change The Result?
- Do Multivitamins Affect Heart-Related Function?
- What Does The WHO Guideline Say?
- How To Choose A Multivitamin
- References
Are Multivitamins Really "Expensive Urine"?
Partly. It depends entirely on the product, and the official position is more nuanced than the slogan.
In 2022 the US Preventive Services Task Force, the independent American prevention panel, reviewed multivitamins for the prevention of cardiovascular disease and cancer. Its verdict was an "I" grade: the evidence is insufficient to weigh benefits against harms [1]. That is not an endorsement, but it is also not a recommendation against.
The contrast within that same review is instructive. The panel concluded that the harms of beta-carotene outweigh its benefits, and that vitamin E offers no net benefit [1]. It was willing to issue a clear negative where it thought one was warranted. For multivitamins as a category, it declined to — because the data were not there yet.
"Insufficient evidence" describes a moment in time. The sections below cover what has arrived since.
Why Does A Multivitamin Turn Urine Bright Yellow?
The bright yellow colour comes from riboflavin, also called vitamin B2. Riboflavin belongs to a group of compounds named flavins, after the Latin word for yellow, and it is absorbed very efficiently from the gut [7].
The familiar criticism attached to that colour is accurate as far as it goes. Absorption from a single dose has a ceiling, and the recommended daily intake of riboflavin is just 1.3 mg [8]. Anything the body cannot use is excreted.
Many multivitamins and B-complex products nonetheless contain riboflavin at doses orders of magnitude above the recommended intake. In those products the criticism lands squarely: the surplus is excreted, and the vivid yellow is the visible proof of it.
The conclusion to draw is about dosing rather than about multivitamins as a class. A formula built around recommended intakes behaves very differently from one built around headline-grabbing percentages.
Which Vitamins Are Risky At High Doses?
Several, and the evidence comes from large randomised trials rather than from theory.
Beta-carotene is the clearest example. During the 1990s two large trials gave high-dose beta-carotene to smokers in the expectation of preventing lung cancer. The Finnish ATBC trial instead recorded an 18 per cent higher incidence of lung cancer among the men receiving it [3]. The American CARET trial, which paired 30 mg of beta-carotene with retinol, found a lung cancer relative risk of 1.28 and was halted early [4]. The doses differed between the two trials — 30 mg in CARET, 20 mg in ATBC — and are often incorrectly reported as a single figure.
Vitamin E has its own signal. In the SELECT trial, men assigned to high-dose vitamin E developed prostate cancer at a higher rate than men on placebo [12].
Vitamin D at very high intermittent doses has been associated with more falls and fractures rather than fewer [11]. High-dose vitamin C carries a recognised association with kidney stones.
The pattern across these trials is consistent: the nutrient was not the problem, the dose was. Each of these compounds is essential, and each is obtained safely from food every day. What the trials tested was a pharmacological quantity of a single isolated nutrient, sustained for years — a very different exposure from the amounts present in a diet or in a formula built around recommended intakes.
Is High-Dose Vitamin B6 Dangerous?
Australia's Therapeutic Goods Administration has treated it as a genuine safety issue since 2022, when it began requiring a warning label on any product supplying more than 10 mg of vitamin B6 per day, following reports of peripheral nerve damage — tingling, numbness and burning sensations in the feet.
The regulator finalised a stronger decision in November 2025. Oral preparations supplying more than 50 mg and up to 200 mg per maximum recommended daily dose become Pharmacist Only Medicines from 1 June 2027, and more than a hundred listed complementary medicines will have their registrations cancelled [9].
For scale, the recommended daily intake of vitamin B6 is 1.7 mg [10]. Products supplying many multiples of that are common, and switching to an alternative form such as P5P is not a reliable way around the concern.
The regulator also flags a trap worth understanding: the most common symptoms of vitamin B6 toxicity resemble the symptoms of vitamin B6 deficiency [9]. Someone who develops tingling feet may read that a B vitamin helps nerve health and increase the dose, worsening the very problem they are trying to treat.
Can A Multivitamin Support Eye Health?
The eye is where nutrient formulas first produced a hard randomised outcome, and it is also where the field learned to correct itself.
The AREDS trial, published in 2001, gave people with age-related macular degeneration either a vitamin and mineral formula or a placebo. After five years, the risk of moderate vision loss was 19 per cent lower in the supplement group [2]. The outcome measured was vision itself, not a blood marker.
That original formula contained beta-carotene, the nutrient the smoking trials had already implicated. The follow-up study, AREDS2, tested the original against a reformulated version in which beta-carotene was removed and replaced with lutein and zeaxanthin, two pigments that concentrate in the retina.
The reformulation delivered on both fronts. Lung cancer occurred in 2.0 per cent of participants on the beta-carotene formula against 0.9 per cent on the newer one, mostly among former smokers [5]. On a direct head-to-head comparison, the lutein and zeaxanthin version outperformed the original on progression of the condition [6].
AREDS2 is the reason "do supplements work?" is the wrong question. One formula caused harm and its successor did not, because the ingredient list was revised in response to trial data. Formulation, not category, decides the answer.
Do Multivitamins Improve Memory?
This is where the strongest recent evidence sits, and it comes from COSMOS — a trial that randomised more than 21,000 older American adults to a daily off-the-shelf multivitamin or an identical placebo for roughly three and a half years.
The headline outcomes were negative, and that should be stated plainly. COSMOS did not prevent cancer. It did not prevent cardiovascular disease. It did not extend survival.
Cognition was a different story. Three separate research groups ran three cognitive sub-studies within the trial, in three different sets of participants, each with its own placebo comparison. Pooling all three produced a sample of 5,203 people, and the meta-analysis concluded that a daily multivitamin-mineral significantly benefited both global cognition and episodic memory, supporting a role in slowing cognitive decline in older adults [13].
The size of the effect was small — an expected result from sub-studies running around two years, a brief window against the timescale over which cognition changes.
What makes the finding hard to dismiss is its design rather than its magnitude. A large, randomised, placebo-controlled dataset showing a measurable cognitive benefit is a different class of evidence from the observational work that dominated this field previously. Observational studies of supplement users are notoriously difficult to interpret, because people who take a daily multivitamin also tend to differ in diet, income, exercise and healthcare access. Randomisation removes that problem by design, which is precisely why the COSMOS cognitive result carries weight the earlier literature could not.
Does Omega-3 Status Change The Result?
There is an intriguing signal that it might, and it comes from a trial that was not studying multivitamins at all.
VITACOG, run in Oxford, gave older adults with mild memory problems high-dose B vitamins for two years while tracking brain volume on scans. The analysis then divided participants according to how much omega-3 was circulating in their blood at baseline.
Among those who started with high omega-3 levels, B vitamin treatment slowed the rate of brain atrophy by 40 per cent relative to placebo. Among those starting with low omega-3, there was no detectable benefit [14].
The implication is that B vitamins and omega-3 may need each other to show an effect, which would explain why trials testing either nutrient in isolation have so often returned null results. This remains a hypothesis generated by subgroup analysis rather than a settled conclusion, but it is a serious argument for how these nutrients should be tested in future.
Do Multivitamins Affect Heart-Related Function?
A secondary analysis of the COSMOS dataset, presented at the Nutrition 2026 conference, looked at exactly this using the Kansas City Cardiomyopathy Questionnaire — a validated instrument scoring how much cardiac limitation intrudes on ordinary daily activity, from zero to one hundred.
16,027 participants completed the questionnaire annually across three years. The results split in an important way.
Across the full cohort, the multivitamin group recorded a small but statistically significant improvement in symptom burden — the component covering fatigue, swelling and breathlessness. The physical ability score, which covers dressing, bathing, walking and climbing stairs, showed no effect. The clinical summary score, which averages the two, improved slightly [15].
One figure was substantially larger, and it is the only place the researchers used the phrase "clinically meaningful". Among participants with carotid stenosis, a narrowing of the artery in the neck, the multivitamin group scored 7.58 points better than placebo [15] — above the threshold at which a difference becomes noticeable to the person experiencing it.
Two caveats carry real weight here. That subgroup comprised 122 people out of more than sixteen thousand, and the work is a conference abstract that has not yet completed peer review. It is a signal worth testing directly, not a established finding.
What Does The WHO Guideline Say?
In July 2026 the World Health Organization released the second edition of its guideline on reducing the risk of cognitive decline and dementia. It recommended against B vitamins, vitamin E, omega-3 and multivitamins for reducing dementia risk in the absence of a diagnosed deficiency [16].
Read alongside the COSMOS cognitive results, that appears to be a direct contradiction. The explanation lies in the guideline's own methodology.
The word "COSMOS" does not appear anywhere across the guideline's 168 pages. The document states directly that the effects of vitamin and mineral supplementation were not reassessed as part of the update. Supplements were excluded from the evidence review rather than re-examined and rejected.
The supplement question was handled in a single paragraph resting on three review papers, none of which covered the COSMOS cognitive analysis, and concluded that nothing had changed. Functionally, the 2026 recommendation reproduces the 2019 recommendation — a position formed before the COSMOS memory results existed.
This does not make the guideline incorrect. It means the guideline answers an older question than most readers will assume, and it should not be cited as a rebuttal to trials it never assessed.
How To Choose A Multivitamin
No supplement substitutes for a good diet, and the evidence above changes nothing about that. Where a multivitamin is being considered anyway, the trials point to a reasonably consistent set of design principles worth discussing with a doctor.
The recurring lesson from AREDS2, ATBC, CARET, SELECT and the TGA's vitamin B6 decision is that formulation determines whether a product is helpful, wasteful or harmful. Two products sharing the label "multivitamin" can differ so much in which compounds they use and at what doses that the trial evidence for one says nothing at all about the other.
Principles that follow from the trial data:
- Doses near recommended daily intakes rather than hundreds or thousands of per cent above them.
- Lutein and zeaxanthin rather than beta-carotene — the pairing that replaced it in AREDS2 and carries the trial data.
- Caution around vitamin A and vitamin E, given the safety signals recorded in the trials above.
- Chelated trace minerals, such as manganese glycinate, which are absorbed well and tend to be gentler on the stomach.
- Vitamin D at sensible rather than megadose levels, alongside vitamin K2, boron and magnesium, which may act together on bone health. K2's blood-vessel data remains weaker and needs hard outcome trials measuring heart attacks and strokes, not imaging alone.
- Third-party testing, from independent services such as labdoor.com.
From the MicroVitamin range
MicroVitamin was formulated around these principles: it includes lutein and zeaxanthin rather than beta-carotene, uses chelated forms for its trace minerals, and keeps its B vitamins near recommended daily intakes rather than at megadose levels. See the full ingredient list and doses on MicroVitamin.
The honest summary is that the worst multivitamins deserve the reputation the whole category inherited, and a few of them are actively worth avoiding. What has changed is that specific, well-designed formulas now have randomised placebo-controlled evidence behind them on cognition and eye health. That is a materially different position from the one the "expensive urine" line described in 2007.
References
1. https://jamanetwork.com/journals/jama/fullarticle/2793446
2. https://pmc.ncbi.nlm.nih.gov/articles/PMC3485447/
3. https://www.nejm.org/doi/full/10.1056/NEJM199404143301501
4. https://www.nejm.org/doi/10.1056/NEJM199605023341802
5. https://jamanetwork.com/journals/jama/fullarticle/1684847
6. https://jamanetwork.com/journals/jamaophthalmology/fullarticle/1790693
7. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7010026/
8. https://ods.od.nih.gov/factsheets/Riboflavin-HealthProfessional/
10. https://ods.od.nih.gov/factsheets/VitaminB6-HealthProfessional/
11. https://pubmed.ncbi.nlm.nih.gov/20460620/
12. https://jamanetwork.com/journals/jama/fullarticle/1104493
13. https://pmc.ncbi.nlm.nih.gov/articles/PMC11103094/
14. https://pubmed.ncbi.nlm.nih.gov/25877495/
15. https://nutrition2026.eventscribe.net/index.asp?presTarget=3453489
