I think both of these things can be true without necessarily contradicting each other. Clearly, vitamins/micronutrients affect your health, especially if you have too much or too little of a particular one. My mother (if I may add my own anecdata point) was having issues with fatigue and energy levels and went through quite a bit of dietary experimentation and analysis until they ultimately ended up giving her a vitamin B (maybe B12?) shot, or rather, a series of such shots, and she said it was like night and day. It fixed her right up.
But most people aren’t my mother.1 And I think that was kind of the point of the study. Not that they can’t help some people, but that supplements are probably useless for most people taking them, and might even make things worse for some.
FTA:
Still, more than half of all adults in the US say they use supplements. Ten percent of us report using four or more each day.
That’s a lot of people taking something they probably don’t need, and some of them will likely be worse for the wear. And I think that’s a point worth raising.
I once heard a nutritionist describe their efficacy as something like “vitamins mostly just give you expensive pee.” The way she phrased it was funnier than that, and she was careful to qualify her skepticism, but the point was that most of whatever nutrient you get from a supplement is going to just pass right through, instead of being absorbed by the body.
That’s a good point. If you can’t get some help identifying the root of a particular complaint, I can totally sympathize with the urge to experiment with whatever potential remedies are available to you. I even get hedging your bets and taking a daily multivitamin “just because”.
But I think there’s also another form of the “how do I know?” question. At the risk of adding to your uncertainty, how do you know that the supplements you’re taking actually contain the nutrients that you think they do, in the dosages that you think you’re getting?
The OP contains a link to another Ars post, that says:
The Food and Drug Administration is not authorized to review supplements for safety and efficacy before they hit the market. That means the bottles and capsules that line the aisles of grocery stores, pharmacies, and specialty shops may not contain what they say they do. They may have wildly variable amounts of supplements in each batch. They may have hidden, illicit components like amphetamines. They may even have harmful contaminants such as lead and cadmium.
The bottom line is that these supplements could contain just about anything, and you have no practical way of knowing what’s really in them. I used to feel like I needed a tin foil hat disclaimer when I talk like this, but given the reality of our neoliberal global economy, late stage capitalism, and all that, I don’t think I actually sound all that wacky. After all, just because you’re paranoid doesn’t mean they’re not out to get you. And we’ve seen plenty of evidence that they really are out to get us (e.g. Purdue Pharma and the Sacklers).
1. which I suppose is kind of tautologically obvious, I’ll admit.