Changing salt-sensitivity

You know how a food can seem too salty, or not salty enough? Does anyone know what goes into that?

A few observations:

1) My grandma died at 97 four years ago and both of her children (my mom and uncle) predeceased her, so I spent a fair amount of effort helping her out as I could. I noticed that she was just incredibly picky about salt. She'd want salt added to unsalted food I cooked for her, but it was extremely easy to oversalt it and then she would reject it. I observed this over something like fifteen years and I think she was getting pickier about it over time.

2) I do most of our cooking and love chiles. Our food has gotten hotter and hotter over time. My wife (especially, but I generally agree with her) is much more likely to assert that a dish is oversalted if it's quite spicy. When I had this observation, I googled around and found some corroboration, so I think it's a real phenomenon, though it wasn't something I ever hear chile-heads talk about.

3) My wife and I are ~54 and we both think that we're more sensitive to too much salt than we used to be.

4) My own window to tolerance for salt is wider than my wife's. It mostly doesn't occur to me to add salt to stuff, even when I agree after the fact that salting it improved it. And I'm more likely to eat something without noticing that it's too salty than she is - I'm particularly thinking about salty fermented condiments. I wonder what goes into caring more or less.

So on first look, it seems like maybe there's a thing where salt-sensitivity increases as you age. But I haven't controlled for other variables. Maybe it's down to increased dietary capsicum exposure. Or maybe it's brought on by our increased likelihood of eating actually cooked from simple whole foods meals rather than boxed stuff or fast-food. Or something else entirely that I haven't thought of! It's hard to really think back and apply history to a newly noticed phenomenon with any kind of precision and accuracy.

Anyway, I wanted to put this out there and see if anyone else has observed similar occurrences or even better, knows the biology of salt-sensitivity.

I recently read the book Salt: A World History by Mark Kurlansky that as the title might imply covered the history of salt around the world. Great read - highly recommend. My synopsis won't do it justice, but the author covers a lot of the topics you mentioned regarding how different cultures adopted different processes for adding salt to their diets throughout different periods in time, whether in salty sauces or applying salt directly as a preservative. Adding salt to a dish directly is really only a recent phenomenon since we can now refrigerate food and don't need to use salt as a preservative. I was amazed to learn that people usually had to rinse the salt off their preserved meats so that their food wasn't too salty!

As an avid chef, I am usually pretty aware of what is going into the food I prepare, so I have a good feel for how much salt I am adding to my cooking. As long as I have lots of herbs or other flavorful ingredients, I find there really isn't much of a need to add very much salt. I'll generally add just enough salt to bring out all those wonderful flavors I'm cooking with.

Not sure if you are familiar with the flavor profiles or what is known as the flavor hex (salty, spicy, sweet, sour, bitter, umami). I'm not into fine dining but I do occasionally study some of the techniques the fine dining chefs use, and they emphasize using the different profiles to balance out and enhance a dish or meal. I don't think salty and spicy are generally considered to have a relationship, but I know salty and sweet are considered to enhance one another (such as salted caramel), whereas as spicy and sweet are considered to balance one another (such as sweet and spicy chicken).

As far as changing salt sensitivity, I know from personal experience that it is definitely a thing in the short term. Due to my work, I have to endure 6+ month periods every couple of years where my only food options are a diet of highly processed foods. These foods of course contain high amounts of salt. When these periods of time are over and I return to my normal diet of home cooked meals, I notice my body very clearly craving salt for a couple of weeks. Not sure how to describe it, but it is an obvious physiological reaction. Essentially a withdrawal symptom.

Going back to the book though, this can be an expected trait for naturally selected species. Salt of course is needed for our bodies to function, so species (including humans), have been driven to seek it out in nature. Animals know where salt licks are or which plants they can eat to get salt (even if just trace amounts). Hunter-gatherers would make treks to the ocean on regular occasions to harvest salt. So, it is only natural that when our body has an abundant supply of it, we are inclined to eat and store as much as possible (especially when combined with simple carbohydrates, as in an entire bag of potato chips), and when we force ourselves to part with that abundant supply, our body will give us signs of discomfort to encourage us back to it.

Regarding salt sensitivity increasing or decreasing with age, I think that would be completely plausible, especially in our age of abundance. Our bodies evolved in societies that probably consumed relatively stable amounts of salt over generations. For the most part, our ancestors probably consumed the same amount of salt over the course of their lives (although perhaps in a cyclical nature), and that amount was probably about the same as the generations before and after them. And as a society, they wouldn't have had nearly as much individual choice on how much salt they consumed. We on the other hand, can rapidly change our diet whenever we want and can make extremely different choices as individuals or families on what we eat. Compound these effects over the years and I can definitely see it causing a some to be more sensitive to salt and some to be less sensitive to salt.