How Does Salt (Sodium) Raise Your Blood Pressure (Explanation Made Simple to Understand!)
Let’s take a moment to talk about salt and it’s effects on your body. Specifically, I wanted to talk about how it can raise your blood pressure. By better understanding the effects of salt on your blood pressure, you may be better able to manage that aspect of your health moving forward.
Before I get started, I want to mention that salt has many roles in the human body and I’m going to specifically focus on blood pressure in this lecture.
In a nutshell, sodium (or Na+), which I’ll just refer to as salt ( NaCl) for now, helps your kidneys retain water. This serves a very essential function to our overall health and well being. The salt circulating in our bloodstream, and in the rest of our body, helps keep our circulatory system filled and allows the heart to do its job of delivering oxygen around the body.
When we exercise and sweat, or when we sweat because of elevated temperature, we lose heat, water and salt (among other things). The sweat is important because we can regulate our body temperature under these various stressors. The salt in your bloodstream also helps keep fluid there under these stressful conditions, keeping your blood pressure within a normal range despite the fluid loss from sweat. Obviously, over time, if you don’t rehydrate you will run into issues related to dehydration (think of athletes or of someone crossing the desert without water).
It is the job of your kidneys to regulate the amount of salt in your circulatory system. If total salt goes up, your kidneys will filter more out. If total salt goes down, those filters will close and your body will try to retain salt. This affects your blood pressure directly because the water “follows” the salt if you will. It does this through a physical process called osmosis.
Osmosis is a process by which a fluid (water in this case) spontaneously moves to an area of higher molecular concentration (more salt molecules). In this picture, you see a beaker with a semi-permeable membrane that the pink stuff which we’ll call water can penetrate. The purple dots, which we’ll call salt, can not penetrate.
In the first beaker, on the left side of the membrane there are only 7 molecules of salt, and on the right there are more like 20. Because the concentration of salt in water is higher on the right, it will pull water through the membrane until both sides have the same concentration. In the right beaker, we see that most of the water is now on the right side of that semi-permeable membrane. Think of it like the salt is forcing the ratio of water to salt to equilibrate or to become the same on both sides by pulling the water across.
In the human body, if you have a higher salt concentration or retention in your circulatory system, more water will be retained. If you increase the salt filtering and excreting through your kidneys, water will follow it out and enter your bladder as urine.
Osmosis is a conceptually difficult topic, and if my overly simplified explanation doesn't make sense, I would encourage you to look it up on youtube, there are several great videos that explain it more thoroughly.
Now everything I have explained there is the normal, healthy way our body regulates our levels of salt. There are a lot of other factors at play here including hormones, other electrolytes besides sodium, etc, but this is really just to give you a simplified sense of how this works.
Unfortunately, the process is not perfect, and things can go wrong. This can occur because of too much salt intake, because of heart problems that make it sensitive to fluid overload and/or because of kidney problems that cause the filter to not work properly. In all of these cases, you can end up with more sodium in your bloodstream, leading to more water retention and higher blood pressure. This is one cause of the disease process known as hypertension (of which there are many).
According to the American Heart Association, we require about 1500 mgs of salt per day. As Americans, we consume about 3,400 mg/day, more than twice what we need. Furthermore, 75% of the salt we consume comes from processed food and restaurant, and less than 25% from what we add ourselves. It’s also worth noting that some people are more sensitive to salt intake than others. So if you have no heart or kidney problems, you’re most likely able to filter out the excess salt. However, if you have heart or kidney issues, or you are particularly sensitive, then the excess salt can start causing problems and potentially damage some of your organ systems.
In your kidneys, it can continue to damage them, leading to inability to filter your blood and all the various molecules in it. This can lead to a buildup of toxic products in your bloodstream.
The elevated blood pressure can also stiffen your arteries, causing the walls to become thicker and stronger and the artery itself can become narrower. This is a compensatory mechanism but not necessarily a good one. Over time, those thickened blood vessels can increase your risk of blood clots, heart attacks and strokes.
It can also damage your heart. One way it does this is make your heart pump harder against the elevated blood pressure, causing it to enlarge. It can also stress the coronary arteries of the heart increasing your risk of heart attack.
Increased blood pressure is also linked to arterial damage in the brain. Over time, it can reduce blood flow, increasing the risk of dementia and stroke. Elevated sodium is also associated with osteoporosis, stomach cancer, kidney stones and headaches.