Diet and Digression: Why is too much salt bad for us?

Salt, or sodium chloride, is essential for humans to survive. But why? And why is too much a bad thing?

Is salt good for us?

Salt is very important in things like muscle contraction (including keeping your heart beating), nerve conduction (e.g. when you accidentally touch a hot stove, you feel pain and perhaps shame depending on how often said incident occurs—both are controlled by nerve impulses), and, among many other functions, in keeping the cells in our body alive.

Nerdy aside: Salt plays a crucial role in maintaining the electrical gradient of our cells. Essentially, the cells in our bodies have a slight electrical charge. Among many other receptors, there is one (called the sodium potassium ATPase) that pushes sodium out of cells in exchange for bringing potassium into cells. Both sodium and potassium are positively charged, but the receptor pushes out more sodium than it brings in potassium, leading to a negative electrical charge within our cells.

We need water. But without salt, our bodies would not be able to properly utilize water. Water has a property known as osmosis. Essentially, osmosis is the ability to travel from one compartment to another (e.g. from outside of a cell to inside of a cell) without using energy. Within our body, the most important regulator of this process is typically salt. So an absence of salt leads to water not being able to properly enter tissues, cells, and other parts of our bodies where it is needed.

Then what’s the problem?

We need some salt. If you look at the recommended daily intake on the back of food products, sodium will always be there as something that we should be consuming. The problem is that we sometimes eat way too much, especially when eating certain types of foods.

Salt alters the flavor to food (taste receptors on the tongue respond directly, among other things, to sodium). In addition, salt can help preserve foods because too much salt can be dangerous/deadly even to bacteria. As a result of our affinity for salty foods and its ability to increase the shelf-life of food, salt has made its way as a staple into our diet.

Before the days of canned foods and McDonalds, some individuals used to salt or smoke meat to keep it from spoiling.
Goiter and other thyroid conditions can result from a lack of dietary iodine. Beginning in 1924, iodized salt was introduced to the U.S. market. Most salt in the U.S. is now iodized, meaning it contains iodine, greatly reducing the incidence of goiter

Americans typically eat too much salt. To understand part of why this is a bad thing, we’ll need to talk about the concept of osmosis brought up earlier.

Say you have a single cell floating in a blood vessel. If you then add a bunch of salt into the blood vessel, but not the cell, water will immediately flow outside of the cell. Once it loses water, there is less volume in the cell, so it will shrink. As I’m sure you can imagine, our cells aren’t too crazy about that, so our kidneys hold on to more water in order to get our cell back up to normal size. But in order to do this, additional water has to be added to blood vessels too. So the end result is that our cells stay a normal size, and our blood vessels have more water in them. This increases the pressure inside our blood vessels. When the body cannot adjust appropriately, this results in hypertension.

Hypertension isn’t a good thing. It’s generally defined as a blood pressure higher than 140/90. Hypertension increases the likelihood of heart attack, stroke, and all sorts of bad things.

Hypertension implies a high-pressure system in your blood vessels. Much like a pressure washer can do more damage than a hose with a weak stream, higher pressure can damage the walls of our blood vessels. Damaged vessel walls enable things that have no business in our blood vessels to enter into the walls, leading to inflammation, atherosclerosis (essentially hardening and narrowing of arteries), and other negative effects.

So, in short, too much salt over a long period of time can increase the risk of developing hypertension. Hypertension is a bad thing.

Diet and Digression