In essence, your body knows better than the experts how much salt it needs—and telling someone to restrict their salt intake is akin to telling someone to restrict their water intake when they are thirsty. It just makes no biological sense. So how did this myth get started? Some experts used population data to suggest that salt intake will increase when it is introduced to societies that do not use a lot of salt. Norman K. Hollenberg of Harvard Medical School termed it a “habituation” that can develop with salt intake, similar to what happens with alcohol, tobacco, and coffee, all of which are habit-forming. However, this increased intake does not mean salt is habit-forming—it’s actually evidence that if enough salt is available, people will consume more, but only up to a physiologically determined set point, one that provides ideal health and longevity. Indeed, when salt is freely accessible, people across numerous populations tend to eat an amount that stays within a remarkably narrow range, generally between 3 and 4 grams of sodium per day. When salt is freely available, even animals consume an amount almost exactly proportional to humans’ instinctive intake. This consistency supports the idea of an evolutionary “salt set point” that resides in both humans and animals. Our salt intake is unconsciously controlled by our internal salt thermostat. What may look from the outside like salt “addiction” may actually be a reflection of the flux in salt storage. Interestingly, salt can be stored in the skin—similar to the way a camel stores fat in its hump, but distributed widely and invisibly—via a mechanism that appears to be controlled by certain hormones that are produced within the body. Some have proposed that aldosterone increases those salt stores in the skin, whereas cortisol may deplete those stores. (Recall that aldosterone also helps the body retain salt during salt depletion.) When we aren’t eating enough salt, aldosterone increases, which in turn stores salt in the skin. People who have consumed low-salt diets their entire lives, such as those in primitive societies, automatically switch over to eating more salt once it’s introduced, and the higher salt intake may cause the body to lose some of its salt stores in the skin. The reduced amount of salt in the skin may be a signal to continue to eat the salt in the range of 8 to 10 grams per day. In essence, the fact that certain low-salt-eating people begin to consume more salt once it’s introduced may have nothing to do with salt being addictive—and everything to do with human physiology. They’re simply eating more because those hidden salt stores in the body have gone down because of the increased salt supply in their environment. Also, don’t forget that compared to a low-salt diet, a normal-salt diet seems to place less stress on the body—so instead of the body continuously trying to retain more salt through the chronic activation of salt-retaining hormones (which requires a lot of energy), it can simply get the salt it needs through the diet and not worry about having to reabsorb as much at the kidneys. And let’s face it, why would the body choose to take in less salt if doing so puts more stress on its organs? Indeed, our internal salt thermostat seems to drive us to consume an amount of salt that places the least stress on our body.
The last excerpt from this book. Unlike other substances (like sugar), salt is not something that we can get addicted to. Generally, we tend to consume the amount that is just right for the body. While low-salt populations might increase their salt intake when faced with salt, they generally tend to stop a certain level, indicating that our bodies do have a way to regulate the amount of salt we need.
