Should I take vitamins?
Many, many readers
Two notes up top.
First: if you have a specific vitamin deficiency, vitamins will help. If you have scurvy, vitamin C supplements (or citrus fruit, raw seal meat, ketchup, etc.) will address the problem. The key thing to realize is simply that mostly you do not have a deficiency and that more isn’t necessarily better. Many of the questions I got were of the form “I have this deficiency…”, in which case, yes, you should take vitamins. The caution is that “low” levels of something but within a normal range is not the same as deficient.
Second: there are a lot of very small randomized vitamin trials that show various benefits. Often these fly in the face of other trials that do not show benefits. It is likely that many of these trials are effectively false positives — they often evince what we call “p-hacking,” or are subject to publication bias; more on this below. Small trials = caution.
Vitamin Roundup
“What about the interaction between multiple vitamins/minerals taken together? I’m not strongly attached to or against vitamins in general, but it seems that the new vitamin D study fails to account for this (from reading the abstract). Some vitamins impact absorption of other vitamins/minerals (therefore impacting effectiveness or lack thereof).”
It’s hard to rule things like this out. There’s always going to be an argument like “Well, sure, vitamin E has no benefit on average, but if you also take essence of mugwort and three drops of canola oil and turn in a circle while you do it, you get incredible benefits.” We’ll never know! From a biological standpoint, this seems unlikely. It’s not impossible, but I think what we can glean from the data is that while effects may vary across groups, they aren’t enormous for anyone.
“I live in the Pacific Northwest, and there is a big emphasis on taking vitamin D supplements since we don’t get a lot of sun for much of the year. Is this supported by data?”
Vitamin D levels increase as a result of sun exposure. However: in the vitamin D trials, researchers didn’t see benefits even among people with low vitamin D levels, so the data support here is fairly weak.
“My primary-care doc has been dismissing vitamins for years. But since taking zinc right when my toddler gets a cold, I’ve been able to fight all of them off. Before that, I got every single one. I even say as I’m taking them, I don’t care if it’s placebo as long as it works! Haha.”
The placebo effect is a pretty good effect. In this case, there is a bit of randomized trial evidence supporting the value of zinc for lowering the duration of cold symptoms. So maybe you’re getting mostly placebo, with some real impact.
“What about vitamin C and/or elderberry for colds or if someone around you has a cold, or for cold season in general?”
The trial evidence for vitamin C and colds is all over the map. General supplementation doesn’t seem to prevent colds. Some studies show that regular supplementation reduces the duration of colds, but not supplementation that starts during the cold. If you were going to pursue this, the evidence is more strongly in support of using it during the whole cold season, rather than just when you get sick. Maybe your cold will be a day shorter. Maybe.
Elderberry has no clear positive evidence.
“What about calcium for women to prevent or delay osteoarthritis, especially for those most prone to it? Docs seem to recommend it.”
This is a standard recommendation for older women at higher risk of osteoarthritis. Summary evidence suggests that calcium supplements may have a small impact on bone density (a 1% to 2% increase), but there’s no compelling support for an impact on fracture risk. This is an “absence of harm” recommendation, but not one that seems like it would have large impacts.
“I thought it overwhelming when trying to decide what to take, so I only took C when sick. But I did have a micronutrient blood test recently, and it showed what I needed to take. Any thoughts on those?”
For something in the range of $300 to $500, these tests can tell you your levels of micronutrients.
And then…?
As I’ve said before, it’s not at all clear that vitamins follow a more-is-better pattern. So it’s not obvious the action item you’d get from knowing that you are, say, a person with lower-than-average vitamin E. Adequate vitamin levels are an important health goal. Especially high vitamin levels are not.
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