CWeak evidence, or evidence againstOther
The short answer
Large trials have repeatedly failed to show that multivitamins prevent disease in well-fed people. Nutritional insurance that mostly insures against nothing.
Who this is actually for
People with genuinely erratic diets, malabsorption, or after bariatric surgery.
What it is legally allowed to claim
Nothing. There is no authorised EU health claim for this substance, so any packet promising a specific benefit is making a claim it is not entitled to make. That is worth knowing before you judge the price.
How much is too much
Varies by product. Check that no single nutrient exceeds its upper level.
Cautions and interactions
Many contain doses far above the reference intake for no benefit. Avoid ones with high vitamin A if you could become pregnant.
Ask a pharmacist before you start anything. Interactions with prescribed medicines are the most common way supplements cause harm, and they are easy to check. Bring the actual packet, or a photo of the ingredients panel, because doses and forms vary enormously between products. Nothing here is a substitute for advice about your own situation.