Home / Multivitamins / Guide
Multivitamins · Weak evidence
Is taking a multivitamin worth it
The short answer. A multivitamin corrects deficiencies; it does not improve the performance of people who do not have them. In well-fed people, sports nutrition reviews find no ergogenic effect. Its value lies in filling a specific gap, and to find out whether you have that gap there is a better tool than a tub: a blood test. It is also the only category on this site that is not scored, because there is no single reference dose for twenty micronutrients at once.
Reviews find no consistent effect. It is listed because it sells, not because it works. No figure on this page is attributed to a specific product: the effect belongs to the ingredient and every number carries its source next to it.
01 What it does and how much
Each row is a measured effect, with the figure the study gives and the source number. Where the evidence gives no figure, the column says so instead of making up a percentage.
| Effect | How much | Detail |
|---|---|---|
| Performance in people without deficiencies | no effect | It is the consistent finding: where there is no deficiency, correcting one adds nothing. A micronutrient is not a lever you can push above normal to perform better. [1] |
| Performance in people with a deficiency | corrects it | Here there is an effect, and it can be large. But then what is needed is to correct THAT deficiency at its dose, not a tub with twenty things at small doses. [1] |
| Comparable reference dose | does not exist | Twenty micronutrients with different reference values cannot be reduced to one effective dose. That is why this category is listed with its price per capsule and no score: scoring it would mean making up the criterion. [1] |
02 How to take it
- Dose. The one on the pack, checking that no micronutrient shoots far above its reference value.
- When. With a meal. Vitamins A, D, E and K need fat to be absorbed.
- How long before you notice it. If it corrects a real deficiency, weeks or months depending on the nutrient.
Details that change the result
- More is not better. Fat-soluble vitamins (A, D, E, K) accumulate and at high doses can cause problems, unlike water-soluble ones.
- The deficiencies that genuinely recur have names: vitamin D in people who spend the day indoors, B12 on vegan diets, iron in women with heavy periods. All three are measured with a blood test and corrected with their own supplement at its dose.
- A multivitamin with caffeine or "energising" extracts is not a multivitamin: it is something else with vitamins in it.
- It does not replace eating vegetables and fruit. The food matrix provides fibre and compounds the tub does not.
03 When it makes sense and when it does not
Worth it if
- A restrictive diet by choice or necessity, with few food groups.
- Vegan diet, above all for B12, which is not optional there.
- Little sun exposure for months, for vitamin D.
- Repeated deficiencies in blood tests, and in that case the specific nutrient beats the multi.
Not worth it if
- As generic insurance without knowing whether anything is missing. A blood test is usually cheaper and more useful.
- Hoping for more energy or performance without any deficiency.
- To make up for a bad diet. The hole is in the diet and stays there.
04 Sources
Every figure above comes from here. They are position stands from scientific societies, meta-analyses and peer-reviewed reviews: if a claim cannot hang from one of these lines, it is not on the page. References are cited in their original form.
- Kerksick CM et al. ISSN exercise & sports nutrition review update: research & recommendations. J Int Soc Sports Nutr. 2018;15:38. Los micronutrientes solo mejoran el rendimiento cuando corrigen un deficit previo. doi:10.1186/s12970-018-0242-y
This is not medical advice. It is what some studies say about an ingredient, not a protocol for you. With an illness, medication or pregnancy involved, the decision belongs to a healthcare professional who knows you.
Questions about multivitamin
Answered with the data on this page
- Is a multivitamin any use if I eat well?
- If you eat a varied diet and have no deficiencies, sports nutrition reviews find no effect on performance. Correcting a deficiency that does not exist improves nothing. Where it does help is when there is a real gap, and a blood test tells you that.
- Which vitamins genuinely tend to be lacking?
- Three keep coming up: vitamin D in people who spend the day indoors, B12 on strict vegan or vegetarian diets, and iron in women with heavy menstrual losses. All three are measured in a routine blood test and are better corrected with the specific supplement at its dose than with a multi.
- Why do multivitamins have no score on this site?
- Because there is no honest way to score them. This site’s score compares an active’s dose with a cited reference dose, and a multivitamin carries twenty micronutrients with different reference values. Inventing an effective dose for the whole would mean inventing the criterion, so the category is listed by price per capsule with no score.
- Is taking too many vitamins bad?
- It can be with fat-soluble ones. A, D, E and K accumulate in the body, and at high sustained doses they can cause problems. Water-soluble ones like C and the B group are cleared more easily in urine, so there what you mostly lose is money.
And now, which to buy
Prices, kept apart from the evidence
This page explains what multivitamin does and deliberately names no brand. The comparison is the other half: 114 products from 12 stores from €0.027 per capsule, sorted by price and by how verifiable their certification is.
Other guides
What each supplement does, with its sources