Interesting look at the history (and uselessness) of taking vitamin supplements.
As it turns out, we do actually need vitamins to live and we die, often horribly, if we don’t have enough. And there are certainly plenty of places in the world where people don’t have enough, and do die horribly because of it. My dad, for (a non-death-related) example, came to Australia by boat as a child in the 1950s. There’s a photo of him, not long after he arrived here, standing in front of a fence and… kinda leaning funny to one side. That’s because his pants are nailed to the wood to keep him upright; he’d developed rickets (lack of vitamin D, a.k.a. sunlight) on the ship and couldn’t stand on his own.
He’s okay now, some 60 years later, but still has some lingering skeletal issues from his childhood.
For most people living in modern industrial countries, however, it’s actually really, really difficult to develop something like rickets, in part because basically everything we eat is loaded to the brim with synthetic vitamins anyway, whether or not they would’ve existed in the original food product. I remember many years ago a bunch of guys on the internet decided to try and contract scurvy as a way of getting out of their final end-of-year exams. It was difficult for them to find foods they could actually eat that would, a) keep them alive, but b) had a low enough vitamin C content. Even most junk food was out, because even a single slice of pizza generally has enough tomato paste on it to keep scurvy at bay.
Point being: you probably don’t actually need vitamin supplements unless you, like, plan on sailing on a tall ship for six months eating nothing but hardtack.