Next week’s Q&A will focus on school. Have questions? Submit them here!

A couple of weeks ago, I wrote a long post on vitamins, with the frame that, for the most part, you do not need vitamin supplements. People had follow-up questions! I’m going to try to answer some of the most popular ones today. As always, the first question — on prenatals — is open to everyone, and then there are a bunch more behind the paywall. (This is a good day for subscribing if you’ve been thinking about it…)

Before getting into this, though, let’s set the stage with two broad points.

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.

With that: some questions (I’m trying some rapid-fire responses here)…

Prenatals 

“Can we talk about fish oil and choline supplements during pregnancy? I absolutely hated taking the prenatal with fish oil; it made me so nauseous when I had morning sickness. But if there was anything I could do to help my baby’s brain develop, I would do it.”

Fish oil: The Cochrane Review on this topic from 2018 concludes two things: first, we have relatively limited evidence and, second, the evidence we do have gives us no reason to think this supplementation improves cognitive outcomes for kids. More recently, a trial from 2021 suggested that supplementation might cause children, especially boys, to reach milestones earlier. But it’s a good example of some issues with interpreting randomized trials. The researchers only find impacts for boys, they only find impacts on some of the many, many outcomes they consider. It’s a classic example of “p-hacking,” where people try many different subgroup analyses and many different outcomes and selectively report or emphasize only the ones that are statistically significant.  

On top of this,  I’m not sure how clinically significant it is if your baby stands with help 18 days earlier.

Choline: There are at least three small randomized trials of choline supplementation and infant cognitive performance. They show inconsistent results — the largest one shows no impact; the smallest shows an effect on “processing speed” (measured by how quickly they turn to look at things). It is extremely difficult to measure cognitive performance in 10- to 12-week-old babies, which may relate to some of these effects. But there is nothing in this data that would suggest that choline supplementation is some kind of magic bullet. 

Overall — meh. I definitely do not think this is worth puking for.