I’m in the midst of studying for a final for an intro bio course on physiology. I decided to kill two birds with one stone by writing about something related to what I’m studying. Some of the major topics on the final tomorrow are circulation and salt-water physiology, both really important systems to know in order to understand blood pressure and all that good stuff. So here’s the 411 on our old friend sodium chloride:
To be clear off the bat, some amount of salt is incredibly necessary for many critical physiological functions, namely your nervous system and regulating blood volume. Your blood pressure needs to be above a certain level in order to circulate oxygen and nutrients throughout your body, especially above your heart. Higher salt concentrations in your blood cause you to retain water, which increases your blood volume, which then increases your blood pressure. This system evolved so that when your blood pressure dropped your kidneys would know to stop excreting salt in your urine so you’d retain it and fluid along with it. Nowadays this seems quite silly considering how abundant salt is in our food supply, but for most of the history of the human race, salt was rare. In this way, salt is following the trajectory of fat and sugar in our food system; we evolved to crave it when it was rare, but now we’re still craving it even though it’s no longer rare because evolution hasn’t caught up.
Now, of course, the food industry is well aware that people love salt. 77% or so of our salt intake does not come from us actually adding salt to our food with the salt shaker, but from consuming processed food. Chain restaurants are also notorious for using too much salt in their dishes. Not only does salt keep people coming back for more, but it also helps preserve packaged food. The result is that along with too much animal fat and refined sugar, as a population we’re consuming WAY too much salt.
So what’s the problem with this? Well, like I said, when you eat a lotta salt, your blood pressure goes up in response immediately. There is a controversy in the science, though, about whether high salt consumption leads to chronic high blood pressure, aka hypertension. There are also different effects in different people. But if you’re always eating a lot of salt, which most Americans are, then your blood pressure is going to be high a lot. This puts you at higher risk for hypertension, which puts you at higher risk for congestive heart failure and stroke–yuck.
There is a lot of work being done by advocates in Washington to try to limit the amount of salt allowed in packaged and restaurant foods, which will probably take years. In the mean time, I suggest you limit your intake of processed foods and eat out less, for a whole host of reasons including excess salt. In cooking your own food you’ll use less salt in general, and you can also purposefully flavor your food with herbs instead.
And with that, I return to studying. Wish me luck!