Do Multivitamins Actually Work?
About one-third of all adults in the United States take a multivitamin/mineral supplement, and they’re popular around the world. It sounds like a no-brainer – the more vitamins and minerals, the better, right?
Well, that isn’t actually as clear as you might think.
Multivitamins Generally Improve Nutrient Intake (But Not Always)
It’s true that multivitamins will generally help when it comes to getting adequate nutrient intake. However, there are some key caveats to keep in mind.
Research does show that both men and women who consume multivitamins are significantly more likely to have adequate nutrient intake. But most adults – multivitamin-users or not – get enough nutrients from their diet.
They also make you more likely to get too much of certain nutrients, like vitamin A. This might not sound too bad, but excessive consumption also carries risks.
Multivitamins Don’t Reduce Mortality Overall
Generally speaking, studies looking at the effect of multivitamin use on all-cause mortality don’t find a difference.
For example, one meta-analysis of randomized controlled trials used a pooled sample of over 91,000 people, with an average age of 62. It didn’t find any difference in mortality risk between people who took multivitamins and those who didn’t. There was a trend towards reduced risk for primary prevention – for participants who didn’t already have a condition – but this didn’t reach significance.
Multivitamins Have Mixed Effects on Specific Conditions
Many studies on multivitamin supplementation look specifically at cardiovascular disease or cancer risk.
One systematic review combined the results of 84 studies with almost 740,000 participants in total and found “little or no benefit” in preventing cardiovascular disease, cancer and death. However, the study found a small benefit of multivitamin use on cancer.
The devil is in the details, though: the absolute risk reduction was 1.2% at most, some vitamins were useless (such as vitamins D and E) and others (beta carotene) actually increased lung cancer risk.
Who Should Take Multivitamins?
The evidence suggests [1] that folic acid, iron, iodine and vitamin D are helpful during pregnancy, vitamin D-fortified milk is good for breastfeeding infants and that adults aged 50 or over should consider B12 supplementation. Other than this and specific deficiencies, there is little benefit to multivitamin use.
