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Does eating salty food really make you thirstier?

It's conventional wisdom that eating salty foods makes you thirsty, so you drink more. That's the reasoning, or so it's said, behind those salty snacks served in bars: they make you thirsty, so you buy more drinks and the bars make more money.

There are those who see this same reasoning as applicable to the obesity epidemic: if eating more salt makes us thirsty, then consuming an overly-salty diet makes us drink more sugary beverages, which contribute excessive calories to our diets and cause us to gain weight.

As with a lot of "old wives' tales" or conventional wisdom, however, nobody's actually tested this phenomenon to see if there's any actual truth in it. Until researchers in Israel devised a way to test it, however. In a study published in Appetite (2015;85:70-75), a team invited a total of 58 male and female psychology students to participate in what was described as a tasting session in return for study credits. On three separate occasions, each participant visited the lab and were asked to eat and evaluate a selection of mixed nuts, followed by a measure of hunger, thirst, and satiety along with a more general demographic and dietary questionnaire. They were then asked to wait 90 minutes, during which they were provided with water and access to the Internet, then they again evaluated the nuts they had eaten over an hour before. The only difference between the three visits was that the selection of mixed nuts was either unsalted, sweetened, or salted.

The true aim of the study was to evaluate how much water the participants drank after eating each "flavor" of mixed nuts. For the two hours prior to the laboratory visit, the participants were asked to refrain from eating, smoking, or drinking anything other than water - so the researchers knew that the participants were unlikely to be dehydrated before visiting the lab, and also unaffected by any salty foods they might otherwise have eaten before the lab visit.

The researchers found that the male participants tended to eat more of the nuts than the female participants, regardless of the nuts' flavor, but also tended to drink more water. When they took body weight into account, however, men and women tended to drink about the same amount of water in relation to the amount of nuts they ate, with no significant difference between salted, unsalted, or sweetened nuts.

What this means for you

The researchers might have put it best: "The findings... suggest that bar-owners can reduce the sodium content of their titbits without compromising their drink sales or customer health." You may not be a bar owner yourself, but this should stop you from telling yourself that you're thirstier because you ate those salty nuts (or snack mix, or potato chips, or....). Further, if you're truly thirsty, in the absence of extreme physical effort, your best choice of beverage is plain, unsweetened water.

First posted: December 24, 2014