Are you being intentionally obtuse? You asked why salt, he answered with literally the most important reason in public health: people actually use it. It is a known delivery vector that works, period.

And, yes, no shit. How to get other people to do something is a fundamental question in life and it just so happens that in life, public health is about getting people to do stuff that's good for their and society's health.

Your question has been answered explicitly twice. Perhaps you are actually asking something else?

Yes. How can we help improve nutrient availability, generally?

From what I pointed out below, this salt processing seems to have underappreciated trade offs. But most importantly, the overarching picture of nutrient availability, not just for iodine, seems to have a bigger challenge at hand worth solving than simply using salt as a vehicle for one - which spirulina would help with in terms of protein and mercury / biotoxin removal, for example.

You fortify staple foods with nutrients. Such as SALT, bread, milk, etc.

The point is that you don't go looking for a new thing for people to consume to get them the nutrients they need, you fortify what they already eat.

Spirulina is not a good source of iodine anyway. Unlike kelp, which grows in iodine-rich ocean waters (and which is a decent source of iodine), spirulina is generally grown in alkaline inland lakes (read: iodine-depleted).

And it this case it appears that spending a buck to iodize a few tons of salt is probably easier or at least easy enough that it doesn't make sense to go through the effort to switch to something else.

Yeah, but salt, unlike many other alternatives, was almost universally used—no challenges getting people to use it—and is ideal as a vehicle. So salt it was.

And, sure, there may have been some other equally good alternatives, but analysis paralysis helps no one. So, salt.

I don't know what idealistic/philosophical point you are trying to make, but we also do things like water fluoridation. Salt happens to be a very convenient medium for iodine.

Or you could dispense with all the uphill iceskating and simply put it in salt.

>Again, by that logic, you could justify anything.

Nope, you could justify very specific pragmatic approaches, just like the parent did.