Some studies up to 2015 surprising found that salty vs. non-salty food doesn't make much difference to thirst. E.g. a 2015 study found that:

However, according to Prof. Leshem, despite our gut feeling that salt increases drinking, this relationship has not been studied in conditions simulating salt-rich foods such as savory appetizers. Therefore, in the present study involving 58 student participants, Prof. Leshem sought to investigate the effect of salt in solid foods on drinking. Participants were scheduled to come to the lab every few days after not having eaten or drunk anything except water, and not having smoked, for two hours. On the days they came, they were asked to taste nuts -- one time sugary candied nuts, another time salted nuts, and yet a third time nuts with no additives. They rated their level of thirst and, during a couple of hours in which they responded to various questionnaires, they got bottles of water. Each subject could drink as much water as he or she wanted.

The main finding was that the level of reported thirst and the actual quantity of water that the subjects drank after eating salty nuts were not different than following consumption of candied nuts or nuts without added flavors. To more deeply examine a possible correlation, the researchers selected the 10 male and 10 female students who had consumed the largest quantities of salt (an average of 4.4 grams and 3.7 grams respectively) and sought to determine whether within this subgroup there was a connection between thirst and drinking, but here too no such correlation was found. This means that even those subjects who consumed larger quantities of salt did not drink more.

This despite the well-known osmotic mechanism that promotes thirst in response to salt intake, and which is verified experimentally in humans, when using hypertonic vs isotonic infusions.

A 2016 study in Nature sheds some light on this issue, basically finding that, in mice at least, SFO-Nos1 neurons anticipate any changes in actual osmotic response; the longer the mice ate, the thirstier they got, well before there were any osmotic changes detected by their brains. Alas, these changes were only detectable using optogenetic photometry, not some non-invasive techniques like fMRI.

So, I'm curious if there are any (post-2016) human studies of thirst due to food ingestion (of various kinds) that attempt to account for the multiple [animal] neural pathways that trigger thirst (which very likely have an equivalent in humans.) E.g. we now expect that thirst might get [almost] equally great eating any kind of peanuts (salty or sweet) in a short time frame, but maybe there's a difference in thirst in a medium (or at least slightly longer) time frame between salty and non-salty peanuts.

  • $\begingroup$ Interesting question and research $\endgroup$ May 13 '19 at 5:15

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