How I found out why walnuts get all the hype and other nuts don't

It was supposed to be a simple idea. I wanted to work out how anti-inflammatory my diet is. There is a ready-made tool for that, the Dietary Inflammatory Index (DII), which turns what you ate into a single score: below zero is anti-inflammatory, above zero is pro-inflammatory. I thought it would take fifteen minutes.

My first score came out pro-inflammatory. It quickly turned out that this was not only the food's fault, but also the app's: in my calorie counter half of the products had no vitamins or minerals filled in. My favourite cheese had zero zinc, and my nut mix zero magnesium. So I started filling in the data, product by product.

With the nuts I was looking up omega-3 and omega-6 and came across a table: hazelnuts, omega-6 to omega-3 ratio 90:1. I thought: oh, great, that's a lot! But then I snapped out of it – of course, it's the other way round. For 90 parts of omega-6 there is one part of omega-3, and omega-3 is exactly what we want. A ratio of 4:1 or less is considered good.

Then I checked the other nuts. Cashews 125:1. And almonds 2010:1. I laughed for a few minutes. Almonds win the category “least omega-3 in the world”.

Finally, walnuts: 4:1. They are the only popular nut with really a lot of omega-3, about 9 g per 100 g. And that is when I finally understood why everyone tells you to eat walnuts specifically, and not just “some nuts”. But as it turned out, that was only halfway to discovering what makes walnuts special.

Because there is a catch. In nuts, omega-3 comes as ALA, the plant form, and the body turns it into the anti-inflammatory EPA and DHA poorly, and in men very poorly. That is why even walnuts will not replace fish or a supplement.

Still, I wanted to dig deeper into walnuts. First I checked the research on whether they calm inflammation. The result was so-so, so I looked for something better. Things got more interesting with the omega-6 to omega-3 ratio: some papers say it matters enormously, others that it does not matter at all. So that is what I put under the microscope.

But since my searches turned up a few “titbits”, I will write about one. Walnuts contain ellagitannins (a type of polyphenol). Gut bacteria turn them into urolithin A, the same compound that, as a supplement, is getting more and more hype in the biohacking world as a mitochondria booster (the cell's power plants). Not to mention that mitochondria themselves are hyped right now 🙂 Interestingly, not everyone's microbiota can make urolithin A: depending on the study, 5–25% of people do not produce it at all (review, 2014).

And this is where it gets interesting, because it turns out that what urolithin A does overlaps to a large extent with the claims about walnuts being “good for the brain”: better brain structure and function, better mood and less inflammation. On top of that, both urolithin A and walnuts are strongly associated with longevity in the public discourse of the longevity world.

But since I wanted to dig into one specific topic around these nuts, I landed on the omega-6/omega-3 ratio – below is what came out of it. And in the conclusions at the bottom, my condensed verdict on walnuts (as condensed as their nutrient density 😉).