Can Salt Increase Your Metabolism?

When it comes to salt, we all know that less is better than more. Scientists, doctors, and public health professionals generally agree on the recommendation to eat no more than 2,300 milligrams, or one teaspoon, of the stuff per day.

But recent groundbreaking research, performed on astronauts, no less, has contradicted much of what we thought we knew about how the body handles salt and even suggests that higher salt intake contributes to weight loss.

In the studies, which were published in two papers in the Journal of Clinical Investigation, researchers put two groups of ten astronauts on a progressively saltier diet and measured their urine output over the course of 28 days. The findings stunned scientists: the higher the salt content of their food, the more urine the astronauts produced, despite not drinking any more fluid than they did on the lower-salt diet. In fact, the study showed that the astronauts actually drank less water when they ate more salt. Where, then, was the fluid coming from?

After performing similar experiments on mice, the researchers found the answer: consuming saltier food led the mice to release higher amounts of a hormone called glucocorticoid, which plays a role in regulating the body’s metabolic rate. The hormone apparently spurred the mice to break down fat and muscle to get more water from these tissues and used that to flush out the extra sodium in their bodies.

This process–which requires quite a bit of energy–also seemed to explain the other unexpected finding of the studies, which was that the astronauts actually felt hungrier on the higher-salt diets. Their bodies were breaking down food for energy more quickly and efficiently with more sodium in the body.

Does this mean that eating a bag of tortilla chips will help you lose a few pounds? Not necessarily. High levels of glucocorticoid can increase your risk of osteoporosis, muscle loss, and Type 2 diabetes. What the research shows, however, is that adding salt to your food doesn’t equal fluid retention and weight gain, which is what scientists and doctors believed for decades. If you want to add some extra salt to your french fries now and then, it turns out that your body may be able to rev itself up to match your craving and be no less healthy or heavier for it.

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