Multivitamin: documented benefits, dosage and risks
A multivitamin combines 10 to 30 micronutrients at nutritional doses: this guide summarises the composition, useful dosages, documented benefits, risks and the profiles for which supplementation is genuinely justified.
Immediate summarykey takeaway
A multivitamin brings together 10 to 30 micronutrients at nutritional doses. Its usefulness is real in case of deficiency, pregnancy or after age 65, but its overall benefit on mortality and cardiovascular risk remains unproven in the healthy adult: it complements the diet without replacing it.
Key facts & entities
Essential points
- 16.8% of Swiss adults aged 35 to 75 take a multivitamin (the Lausanne CoLaus study, more than 6,000 participants).
- The large meta-analyses find no effect on all-cause mortality.
- The COSMOS-Mind trial shows a cognitive gain equivalent to 1.8 years in adults aged 65 and over.
- A prenatal formulation with 400–800 µg of folic acid reduces the risk of neural tube defects (USPSTF grade A).
- The OASM (SR 817.022.32) governs the amounts of vitamins and minerals authorised in Switzerland; 32.7% of products analysed in Lausanne provided less than 15% of the NRV for magnesium.
- Fat-soluble vitamins (A, D, E, K) accumulate in the liver: respect the safety limits and do not combine several supplements.
- Food supplements fill occasional nutritional gaps but do not prevent chronic disease in a healthy adult, and their health effects on heart disease remain unproven.
- Adapt the recommended dosage and the supplement regimen to individual health, dietary restrictions and specific health conditions, ideally after talking with a dietitian, doctor or other health care provider before starting any supplement.
What is a multivitamin?
A multivitamin is a dietary supplement combining at least three vitamins and one mineral, formulated to provide doses close to the nutrient reference values (NRV) rather than high therapeutic doses. Typical commercial formulations contain between 10 and 30 micronutrients, presented as tablets, capsules, soft-gel capsules, powders or liquid ampoules.
Technical definition
Swiss legislation, via the OASM ordinance (SR 817.022.32, status 1st July 2020), regulates the minimum and maximum quantities authorised in every formulation placed on the market. This definition clearly distinguishes the product from a medicine: food supplements aim for basic nutritional coverage, not a pharmacological effect. A daily multivitamin is therefore designed to fill modest nutritional gaps rather than to treat a specific health issue.
Vitamins and minerals most often included
Standard formulations provide all the water-soluble vitamins of the B group (B1, B2, B3, B5, B6, B8, B9, B12), vitamin C, as well as the four fat-soluble vitamins A, D, E and K. On the mineral side, compositions vary more widely: iron, zinc, magnesium, calcium, selenium, iodine and copper are the most common. Differences between brands can reach a factor of 10 for certain minerals such as magnesium or calcium: it is worth carefully examining the nutrients actually present in a formulation.
Each micronutrient the human body needs plays a precise physiological role recognised by EFSA. The B-group vitamins play a central role in normal metabolism: thiamine (often supplied as thiamine mononitrate), biotin and pantothenic acid (as calcium pantothenate) contribute to normal energy-yielding metabolism and to the normal functioning of the nervous system. Vitamin C and zinc contribute to the normal functioning of the immune system and to supporting natural defences. Vitamin E, in the form of tocopherol, helps protect cells from oxidative stress, while beta-carotene is a precursor of vitamin A. Calcium and vitamin D — the latter essential to calcium absorption — contribute to the maintenance of normal bones and to bone health, magnesium contributes to normal muscle function and may help reduce fatigue, and the whole helps support everyday vitality. Some formulations add omega-3 fatty acids from fish oil, an extract rich in EPA and DHA.
Difference from a single-nutrient supplement
The single-nutrient supplement targets a documented deficiency with a high corrective dose, whereas a complete formulation aims for baseline coverage. The distinction is clinical: a patient with serum vitamin D below 50 nmol/L needs 800 to 2,000 IU/day of isolated cholecalciferol, a dose not found in a general-purpose formulation. Conversely, a supplement makes it possible to compensate for modest gaps spread across several micronutrients without focusing on a single deficiency.
Which benefits are actually documented?
Beyond the marketing promises, the scientific reality is nuanced. In a person already well nourished, a supplement is not a miracle health insurance; its best-established benefits concern cognition after age 65 and a modest reduction in total cancer in men.
Cognition in people aged 65 and over
A daily multivitamin taken for three years slows overall cognitive decline in adults aged 65 and over, the equivalent of 1.8 years gained. This result comes from the randomised COSMOS-Mind randomized controlled clinical trial (three-year follow-up), published in Alzheimer’s & Dementia3. An analysis compiling three COSMOS sub-studies10, including the COSMOS-Web arm2, confirms a benefit on overall cognition and episodic memory, more pronounced in people with a history of cardiovascular disease. The effect nonetheless remains conditional on use for several consecutive years.
Total cancer: modest reduction in men
The American Physicians Health Study II (often cited under the title Physicians’ Health Study II), a large randomized controlled clinical trial conducted in nearly 15,000 doctors aged 50 and over and followed for more than ten years, observed a modest but real reduction — of around 8% — in the total cancer risk in the supplemented group compared with placebo1. By contrast, no clear effect was observed on prostate, colon, lung cancer, bladder or breast cancer (the breast cancer signal was assessed in parallel cohorts of women), nor on cancer mortality. Reviews collated by the National Institutes of Health reach the same conclusion: the cancer risk reduction is real but small, and confined to the total cancer endpoint.
Macular degeneration, immune function and other targeted effects
Beyond cognition, two other documented health benefits deserve mention. In age-related macular degeneration, the AREDS and AREDS2 trials (National Eye Institute, National Institutes of Health) showed that a targeted formulation rich in vitamins C and E, zinc, lutein and zeaxanthin slows progression of advanced eye disease in patients already affected; this evidence concerns a specific therapeutic formula, not a generic multivitamin. On immune function, vitamin C, vitamin D, zinc and selenium contribute to the normal functioning of the immune system (EFSA health claims): correcting an insufficient intake supports immune defences, but supraphysiological doses do not produce additional health benefits and may have negative effects. No robust scientific evidence links a daily multivitamin to a reduced risk of heart disease, stroke or other chronic disease in well-nourished adults, and no consistent effect has been shown on skin quality or body weight.
Unproven effects: mortality, cardiovascular, fatigue
Conversely, the large research syntheses show no effect of the supplement on life expectancy: pooling several tens of thousands of participants, the risk of death remains unchanged8, 9. On the cardiovascular side, an analysis pooling more than two million people finds no clear cardiovascular benefit5; the favourable associations observed in some large cohorts remain very modest11. The 2021 major review in the Journal of the American College of Cardiology explicitly concludes that multivitamins, vitamin D, calcium and vitamin C have no preventive effect on major cardiovascular events4. To go further, we detail what studies really establish as advantages.
Dosage, timing and duration of a course
A standard adult formulation provides between 50% and 200% of the nutrient reference values (NRV) for each nutrient included. Above 200% of the NRV, doses leave the nutritional domain and enter a pharmacological logic that warrants medical advice.
The standard dosage of a multivitamin
The FSVO published in 2022 the dietary reference intakes for Switzerland, aligned with those of EFSA. For an adult aged 18 to 65, the recommended amounts are notably 80 mg/day for vitamin C, 15 µg for vitamin D, 700 to 900 µg RE for vitamin A, 2.5 µg for vitamin B12 and 330 mg for magnesium. The precise recommended dosage depends on age, sex and physiological status: women age 30 planning a pregnancy and a sedentary man aged 70 have very different needs, so the daily multivitamin should be matched to the profile rather than chosen by default.
The best time to take it
During a meal containing fats, ideally in the morning or at midday. The fat-soluble vitamins A, D, E and K require the presence of dietary fats to be absorbed via the intestinal chylomicrons; taking them on an empty stomach reduces their bioavailability by a factor of 2 to 3. Morning intake also synchronises the supply of B vitamins with the day’s energy metabolism and avoids the stimulating effect that some high-dose B vitamins can have on sleep. Our guide explains the timing best suited to your rhythm.
Whatever the form — tablet (often one tablet a day), capsule, soft-gel capsule, effervescent tablet to dissolve in a glass of water, or chewable gum — the key is to swallow it during a meal, for example at breakfast, and to follow the stated posology so as to supply each nutrient in sufficient quantity, without exceeding the recommended daily intake.
Duration of a course and frequency of use
A standard course lasts 1 to 3 months, renewable once or twice a year depending on the needs identified. Continuous daily use is justified only for profiles with proven insufficient intakes or increased needs (pregnancy, chronic illness, post-bariatric surgery). Outside these cases, alternating intake periods with breaks allows the actual usefulness of supplementation to be re-evaluated and prevents excessive accumulation of fat-soluble vitamins.
Risks, overdose and contraindications
When properly dosed, a supplement is generally safe, but it is not harmless. The risk concerns above all the fat-soluble vitamins (A, D, E, K) and certain minerals (iron, selenium, zinc), which accumulate in the body and whose chronic overdose can become dangerous.
At normal doses, adverse health effects remain rare; the most common side effects are mild — nausea, stomach upsets or transient diarrhoea — and improve quickly when the daily intake is reduced. Excessive consumption can lead to toxicity, especially with fat-soluble vitamins and iron, and increases the risk of more serious side effects at very high doses; sticking to the recommended dose remains the best prevention.
Tolerable upper intake levels set by EFSA
The European Food Safety Authority (EFSA), the food safety authority of the European Union, updated the tolerable upper intake levels (UL) of several nutrients in 2024. For preformed vitamin A, the UL is maintained at 3,000 µg RE/day in adults, because of teratogenicity and liver risk above that. For iron, EFSA could not set a UL and retained a safe level of 40 mg/day in adults (total intake): the absence of black stools, a sign of unabsorbed iron, was observed up to 20–25 mg/day of supplemental iron. Vitamin D has a UL of 100 µg/day (4,000 IU), above which the risk of hypercalcaemia becomes significant.
| Nutrient | NRV | EFSA limit (UL) |
|---|---|---|
| Vitamin A | 800 µg | 3,000 µg |
| Vitamin D | 5 µg | 100 µg |
| Vitamin E | 12 mg | 300 mg |
| Vitamin C | 80 mg | not established |
| Vitamin B6 | 1.4 mg | 12 mg |
| Folate (B9) | 200 µg | 1,000 µg |
| Vitamin B12 | 2.5 µg | not established |
| Calcium | 800 mg | 2,500 mg |
| Magnesium | 375 mg | 250 mg* |
| Iron | 14 mg | 40 mg** |
| Zinc | 10 mg | 25 mg |
| Iodine | 150 µg | 600 µg |
| Selenium | 55 µg | 255 µg |
Fat-soluble vitamins and liver storage
Vitamins A, D, E and K accumulate in the liver and adipose tissue, which makes their chronic overdose more dangerous than that of water-soluble vitamins. An excess of preformed vitamin A can cause hepatotoxicity, hypercalcaemia, bone damage and, in pregnant women, foetal malformations. Stacking several supplements containing the same fat-soluble vitamins — multivitamin, cod-liver oil, isolated vitamin D — exposes you to a silent excess of the UL. A detailed exploration of the risks of an overdose and the profiles to monitor is needed before any prolonged intake.
Common drug interactions
Vitamin K antagonises the effect of vitamin K antagonist anticoagulants (warfarin, acenocoumarol) — a sudden change in intake can destabilise the INR. Calcium and magnesium reduce the absorption of antibiotics in the tetracycline and quinolone families. High-dose vitamin B6 reduces the efficacy of levodopa in Parkinson’s disease. Anyone on chronic treatment should report supplement intake to their doctor or pharmacist.
How to choose a multivitamin
Five criteria help assess the quality of a supplement: OASM compliance, coverage of micronutrients of interest at nutritional doses, the use of bioavailable forms, the absence of problematic excipients and transparency on the origin of the raw materials.
Criteria of a quality formulation
Prefer bioavailable forms: methylfolate rather than synthetic folic acid, methylcobalamin rather than cyanocobalamin, bisglycinate rather than oxide for minerals. Check the absence of titanium dioxide and artificial flavourings, as well as compliance with the federal OASM ordinance. Our method details every point to identify the formulation that matches your profile.
Reading the nutritional label
The label must show the absolute quantity (in mg or µg) of each nutrient and the corresponding percentage of NRV. According to the OASM, a nutrient must be present at no less than 15% of the nutrient reference value to be listed on the label. Yet a Lausanne study (Marques-Vidal et al., 2014) on 245 multivitamins sold in Switzerland revealed that 32.7% of products showed a magnesium intake below this threshold, 26.1% for copper and 22.6% for calcium7. This frequent non-compliance makes critical label reading essential.
Preferred form
Methylfolate (L-5-MTHF) rather than high-dose synthetic folic acid.
Preferred form
Methylcobalamin rather than cyanocobalamin.
Preferred form
Bisglycinate or citrate; avoid the oxide (bioavailability < 4%).
Preferred form
Cholecalciferol (D3) rather than ergocalciferol (D2).
Also check what the formulation actually contains and how well it is tolerated: a product without lactose or gluten, ideally Swiss-made, limits unpleasant surprises. Match the supplement regimen to your individual health, your specific health conditions and any dietary restrictions (vegan, gluten-free, low-FODMAP) so that the formula supports daily wellbeing without disrupting it. In case of doubt — a proven vitamin deficiency, a restrictive diet, advanced age or ongoing medical follow-up — it is better to consult a healthcare provider: a doctor, pharmacist or registered dietitian can review the label and flag negative interactions. As a precaution, consult with a healthcare professional and talk to your health care provider, or speak to your usual healthcare provider before starting any supplement, especially when other medicines are involved; the same caution applies to other food supplements taken in parallel.
Marketing pitfalls to identify
Four signals warn of a mediocre formulation: the claim “provides 100% of NRV” when minerals are absent or only in traces, therapeutic claims not authorised by EFSA (“cures fatigue”, “boosts defences”), the absence of the precise chemical form, and “all-in-one” formulations exceeding 30 ingredients that sacrifice individual dosages for marketing volume.
For which profiles is supplementation useful?
Needs vary widely from one person to another. Four main situations have a documented clinical benefit: pregnancy, advancing age, restrictive diets and certain medical conditions.
Pregnant women or those planning a pregnancy
The USPSTF (grade A) and the WHO recommend the daily intake of 400 to 800 µg of folic acid at least one month before conception and during the first trimester. This dose reduces the risk of neural tube defects, which affect roughly 1 pregnancy in 1,000 in the absence of supplementation6. A prenatal formulation also provides iron (needs increased by 30%), iodine (150 µg/day per the FSVO) and vitamin D. Preformed vitamin A must be limited to 1,500 µg RE/day during pregnancy.
Age 65 and over
The cognitive benefit documented by the COSMOS trials justifies daily supplementation after age 65, particularly in people with a history of cardiovascular disease3. At this age, digestive absorption of vitamin B12 drops by 30 to 40% and cutaneous synthesis of vitamin D falls by 50% between ages 20 and 70 at equivalent sun exposure: the FSVO explicitly recommends vitamin D supplementation for people aged 60 and over, especially between October and March.
Restrictive diets and medical conditions
Three profiles show a documented clinical benefit: vegans (vitamin B12 must be supplemented, frequent deficits in iron, zinc, omega-3), people after bariatric surgery (lasting malabsorption requiring lifelong supplementation) and patients on long-term treatment affecting absorption (proton-pump inhibitors, metformin, antiepileptics, methotrexate). For people living with chronic disease or several health conditions, the expected health benefits depend on the specific deficiency corrected rather than on the supplement as a whole. High-level athletes and people in convalescence represent transient and targeted indications.
Swiss regulation of multivitamins
The OASM ordinance (SR 817.022.32) is the federal legal basis: it sets the list of vitamins and minerals authorised, the chemical forms allowed and the minimum and maximum quantities for each nutrient.
The OASM, federal legal framework
The FDHA ordinance on the addition of vitamins, minerals and certain other substances to foodstuffs (OASM, SR 817.022.32, status 1st July 2020) governs the composition of supplements. The FSVO (Federal Food Safety and Veterinary Office) is the supervisory authority. A product imported from a third country and not compliant with the OASM cannot be lawfully marketed in Switzerland, even if it is authorised in its country of origin.
Non-compliance observed on the Swiss market
A comprehensive analysis published by Marques-Vidal and colleagues in 2014 in BMC Complementary and Alternative Medicine reviewed all multivitamins marketed in Switzerland containing at least 10 components. Several did not comply with the 15% nutrient reference value rule required to list a nutrient on the label7. This non-compliance concerns mainly minerals whose required volume exceeds the physical capacity of a single capsule. Prefer references whose composition is explicitly OASM-2020-compliant.
Health claims and the EFSA framework
The health claims carried by food supplements in Switzerland follow the European Regulation 1924/2006 as transposed by the FSVO. Only claims validated by the European Food Safety Authority — the EU food safety authority responsible for the scientific assessment of nutrition claims — may appear on the label: “vitamin C contributes to normal collagen formation”, “magnesium contributes to a reduction of tiredness and fatigue”, for example. Any therapeutic wording (“treats”, “cures”, “prevents”) is prohibited and constitutes an offence under the Swiss law on foodstuffs (FSA, art. 18 — misleading information).
Summary
The essentials to remember about supplementation, its documented benefits and its limits.
✅ What is documented
- Cognition: slowing equivalent to 1.8 years after age 65 (COSMOS-Mind)
- Total cancer in men: modest 8% reduction (PHS II)
- Pregnancy: folic acid (400–800 µg) reduces the risk of neural tube defects
- Documented deficiencies and restrictive diets: real clinical benefit
🎯 What is not proven
- No proven effect on all-cause mortality or specific cancers (lung cancer, breast cancer)
- No effect on major cardiovascular events or chronic disease prevention in healthy adults
- Effect on fatigue limited to the correction of a proven deficiency
- A supplement complements the diet, it does not replace it — the overall health benefits remain modest
📌 Safety principles
- Respect the EFSA limits: 3,000 µg RE/day (vitamin A), 100 µg/day (vitamin D), 40 mg/day (iron); going further may lead to toxicity and unwanted health effects
- Take with a meal to absorb the fat-soluble vitamins (A, D, E, K)
- Never combine several supplements containing the same nutrients to limit the common side effects of overlapping intakes
- Check OASM compliance and bioavailable forms on the label
- Report intake to your doctor when on chronic treatment
VitaMix — our multivitamin formulation developed in Switzerland
VitaMix brings together a balanced blend of essential vitamins and minerals — vitamin C, vitamin D, B-vitamin complex, zinc — at nutritional doses, in bioavailable forms compliant with the OASM.
- Essential vitamins and minerals in a single intake
- Nutritional doses aligned with the reference values
- Bioavailable forms, without superfluous excipients
- Developed and made in Switzerland, OASM-compliant
⚠ Dietary supplement. Does not substitute for a varied and balanced diet or a healthy lifestyle. For specific medical indications, consult a healthcare professional.
