Does Wasabi Improve Memory?
Why the headlines are probably wrong about the spicy condiment
Wasabi is a fascinating condiment. It’s incredibly hard to grow, with commercial operations outside of Japan largely failing to reproduce the conditions required to harvest it on masse, which makes it not just rare but extremely expensive. And according to new headlines, in addition to the mystique of expense and rarity, wasabi can cause a “really substantial boost” in people’s memory if they take it every day as a supplement.
While this news seems rosy - memory is a tricky problem to solve, and any improvements in our ability to help older people remember things is a major breakthrough - the reality is definitely a bit less useful. The study behind all this hype isn’t great, and the funding situation is somewhat problematic.
Let’s look at the science behind the claims, where I will finally get to use the phrase Big Wasabi unironically.
The Study
The paper in question is a small randomized trial recently published in the MDPI journal Nutrients. This is a pretty low-quality journal, and in general is not a great starting point for the trial. The study itself is neither terrible nor brilliant - it’s quite a boring example of reasonably good scientific practice with some issues but nothing wildly problematic.
The research consisted of randomizing older Japanese people to either receive a pill containing concentrated wasabi powder or a placebo for 12 weeks. Participants did a range of memory-related tasks before and after this period, and the researchers measured the difference.
Of the 12 outcomes that the researchers reported, there was no difference between the two groups on 8 of them. Both wasabi and placebo improved. For the remaining 4 - tasks relating to episodic and working memory - there was no change in the placebo group, but the wasabi takers had some modest improvements. This led to 4 areas in which the wasabi group had a statistically significant difference to placebo at the end of the trial.
There were some issues with the trial. The reported recruitment and randomization timeline is very strange, with 100% of the patients approached by the researchers agreeing to take part in the study and having full follow-up data. Basic things like allocation concealment - where researchers prevent manipulation of the allocation sequence in the randomization process by ensuring that no one knows which group the next patient is assigned to until the moment of randomization - isn’t really described in the study. The author’s pre-registration differs quite substantially from their publication, with missing secondary outcomes, different inclusion/exclusion criteria, and some other areas where it’s hard to tell if the study was conducted as originally planned.
If we were to take all of this at face value, what we could say is that wasabi may improve some elements of memory by a bit, and others not so much, but you really need a bigger trial to understand if this means anything. But there’s also another aspect of the trial that wasn’t really reported on in the media at all - the funder.
This study was funded by Kinjirushi Co., Ltd., and international company that sells wasabi and wasabi-related products under the tagline “To a tastier and healthier world”. This means that the research here was directly funded by Big Wasabi.
Being industry-funded doesn’t make a study immediately terrible, but it does impact how such studies are conducted and reported. For example, the authors used a fairly complex statistical analysis to find the benefits that they did - if they’d used more basic analyses, the results probably would not have been statistically significant. The authors did not pre-register their statistical analysis plan as far as I can tell, which makes it hard to know if this was the first analysis that they tried, or just the one that got published.
The thing that industry funding really impacts is spin. On most of the outcomes, the placebo group did about the same as the wasabi group, and on a small subset they did slightly worse. So you could just read these results as indicating that wasabi is about as useful as a placebo - and therefore useless - for most aspects of memory, and needs to be investigated further in a few areas in a bigger trial.
Or, as the press release and headlines said, you could just argue that this shows a genuine benefit for the condiment. It’s not a very realistic thing to say, but it’s probably much better at selling the product.
Bottom Line
It’s possible that wasabi has some benefits for memory. In this case, it’s not the wasabi you’d get in a restaurant - you’d have to get concentrated wasabi extract powder packed into small pills - but it’s still a product produced from the root.
It’s also possible, based on these results, that wasabi has few if any benefits for memory. Frankly, given the industry funding and other issues, that seems more likely to me. Unless we see a large independent trial looking at the question in a more rigorous way, I’d be very skeptical of any claims that wasabi is going to substantially improve your brain.
I'll never forget when my mom, a newbie at eating sushi, mistook wasabi for guacamole...or at least that was her excuse for eating a big dab of it.