Multivitamins are the most-bought supplement category and one of the weakest in evidence for healthy adults eating reasonably. Targeted supplementation based on actual deficiencies works better and costs less.
What the evidence shows
Multiple large trials show minimal or no health outcomes from daily multivitamin use in healthy adults. Some excess vitamin intake (A, E, beta-carotene at high doses) may have small negative effects in specific populations.
What targeted supplementation looks like
Vitamin D3 (1000-2000 IU daily, year-round UK). Omega-3 (1-2g daily if not eating oily fish 2x weekly). Iron only if tested deficient. B12 if vegan or over 50. Folate for pregnancy planning. These deliver value where multivitamins don't.
Test what you're actually low in. Supplement that specifically. Skip the daily multivitamin habit unless you're in a population that genuinely benefits (pregnancy, severely restrictive diets, malabsorption conditions).