Except it's the cheaper low-brow canned fish like Sardines that contain more Omega-3s AFAIK.
https://en.wikipedia.org/wiki/Menhaden
which people can't stand to eat.
But I like your hobby!
If the fish is bought frozen, even more of the paid weight is water, so the water content would have to be accounted when comparing prices.
Fish may be much more expensive than it seems when just looking at the price tag, even 50% more expensive per protein content (raw poultry meat has about 25% protein content, while raw fish fillet has between 15% and 20% protein content).
For instance in Japan fish isn't cheap by any measure compared to chicken or pork for instance.
My understanding is that the Omega-3 from these is not particularly bio-avaiable compared to fish/krill oil.
and having only ALA and not EPA/DHA as source of omega-3 will slowly lead to your body be more efficient at transforming (ALA to EPA/DHA)
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6835948/
https://academic.oup.com/ajcn/article/100/suppl_1/449S/45766...
and there is plenty of educative websites searching for “vegan” and omega-3 sources…
Source?
Yes, of course we can not ethically proof that any one supplement has some precise effect, but instead of burying your head in the sand you can follow some general trends.
The point here is that this study didn't prove anything - it's an observational study. The results are consistent with a range of possibilities, not just the ones the study authors were the most interested in promoting to the public. Academic guesses about causation are often wrong, and they're often biased towards what's interesting to academics and what raises the profile of their research. So it's important to highlight other possibilities, especially the "boring" ones that wouldn't get as much attention for the study authors.
There are high-quality studies that actually prove things. For example, we know the impact of lead on IQ because of direct interventions (children who have lead above a certain threshold undergo chelation therapy, so you can compare those right below to those right above).
Here's a book that covers the basics of what we know about intelligence: https://www.amazon.com/Intelligence-That-Matters-Stuart-Ritc...
I have no dog in this race :)
In this case, the correlation has to do with being health-conscious which leads to better health and is linked to ingesting o3. And the reason we argue causation is the simple fact that the mechanism behind the correlation is not explained in a clear chemical way.
In this case, obviously, omega-3s are merely a sign of eating expensive fish, which is a sign of affluence, which is a sign of genetically driven higher mental acuity.