Study Sheds Light on Why Salty Snacks Are So Addictive

Anyone who’s torn through a bowl of popcorn in one sitting knows that salty snacks can be dangerously addictive. A new study published in The Journal of Clinical Investigation [PDF] suggests that more than the snack's taste fuels our insatiable eating habits. The more salt we ingest, the more water we retain, which may leave us still feeling hungry after a snack binge.

As MDC Insights reports, the findings come from a group of international researchers looking at "cosmonauts" on simulated flights to Mars. Two groups, each made up of 10 male volunteers, were fed meals that were identical in every aspect except for salt content. Subjects eating the saltier diet produced more urine, which came as no surprise to the researchers.

It’s the common belief that salty food makes people want to drink more, thus making them pee more. On a Mars mission where every ounce of water equals more money spent on fuel, it's in the cosmonauts’ best interests to keep their drinking to a minimum. Cutting back on salt should help with this, according to the supposed connection between sodium and thirst. But researchers instead found that eating salt actually made the subjects drink less.

The increased urine, the researchers found, was caused by the body’s reaction to salt in its system. Prior to the study, scientists suspected that sodium latched on to water molecules in the body and carried them out through urination. This would make us feel dehydrated and cause us to drink more water. But it turns out the body anticipates this and pulls water back into the kidneys. The sodium, meanwhile, exits the body through the highly salty urine.

Though eating salty diets may help space travelers conserve water, it could also stretch their food budgets. Separate experiments conducted on mice found that dragging water backwards through the body requires increased amounts of urea. Urea, once thought to be just a waste product, binds to the water and helps move it around. But creating urea eats up lots of energy, which made the mice hungry. This could also be the reason why the human cosmonauts complained of feeling hungry when fed saltier foods. Between that and the tricks junk food companies use to get us to keep eating, it’s no wonder a bag of chips is so hard to put down.