Salt is made of two minerals, sodium and chloride.
Sodium, chloride, and potassium are all so closely related to one another that we need to cover them together to make any sense out of them. Today’s lesson will introduce these nutrients, while the next lesson will cover getting them from food and supplements.
These three minerals are all friends, but they each play unique roles in the friendship. Chloride follows sodium wherever he goes, and never leaves his side. Sodium and potassium are always chasing one another, yet endlessly pass by each other in an elusive dance. Potassium is most often found inside a cell, sodium outside. When sodium chases after her by slipping into the cell, she slips out. When sodium takes the bus back home to the outside of the cell, potassium takes the same bus right back in.
This “bus,” known in technical jargon as the “sodium-potassium pump,” consumes 20-40% of our energy at rest. As we will see shortly, it serves to keep sodium (and the chloride that always follows it around) primarily outside cells and to keep potassium primarily inside cells. This separation of salt and potassium is critical to their functions.
Salt and Potassium Are Hydrating
Water has endless admiration for all three minerals. As a result, crowds of water molecules surround the three wherever they go. Since they attract water, they are hydrating. Since potassium hangs out inside cells, potassium primarily hydrates the insides of cells. Since salt hangs out outside cells, salt primarily hydrates the fluid outside your cells. This is called “extracellular fluid,” and it includes your blood.
When you consume food and drinks that contain water, the water has to travel from your intestines to your blood before it can enter your cells. As a result, potassium can’t hydrate your cells alone. Salt must first hydrate your blood and your other extracellular fluids. Then potassium can use that water to hydrate your cells.
This is why it is actually far more hydrating to drink a glass of water with a tiny pinch of salt (about 1/16th of a teaspoon) and some potassium-rich lemon juice (about ½ lemon) than to drink a glass of plain water alone. Similarly, it is more hydrating to drink a small amount of water while eating fresh foods that naturally contain salt and potassium, or that naturally contain potassium and have a little added salt, than it is to drink plain water on an empty stomach. In fact, raw foods tend to contain plenty of water themselves, so as long as you choose potassium-rich raw foods and add a tiny bit of salt, the foods themselves are likely to be very hydrating.
Salt and Potassium Are Electrolytes
The strong attraction between these minerals and water makes them fully dissolve in the water. Minerals that dissolve in water are called electrolytes, and these three are the most important ones. Other major electrolytes include calcium, magnesium, phosphorus, and bicarbonate. Bicarbonate is the only major electrolyte that isn’t a mineral. We consume it in food, it is combined with sodium in baking soda, and we produce it naturally in our metabolism.
Because electrolytes are so fully dissolved in water, loss of water during sweating, vomiting, diarrhea, or excessive urination can cause us to lose them. You may see drinks or packets meant to be mixed with water that are designed to restore electrolytes in those scenarios.
Salt, Potassium, Blood Pressure, and Swelling
If you eat too much salt and not enough potassium, water will make it to your blood and your other extracellular fluids, but your cells could become dehydrated because there isn’t enough potassium to draw the water in.
Potassium is also needed to get rid of excess salt by driving it into your pee. Without it, salt accumulates in your blood, causing the water content of your blood to increase.
As the water content of your blood expands, it exerts more pressure on the walls of your blood vessels, causing high blood pressure.
Further, extracellular fluid in your face, hands, legs, or virtually any part of your body could accumulate and lead to swelling.
High blood pressure itself will force salt into your urine, and that will help bring blood pressure back to normal, and should help relieve any swelling that might be present. Although this allows your system to eventually return to normal, it requires a period of sustained high blood pressure, which raises the risk of cardiovascular diseases such as heart attacks and stroke. Consuming adequate potassium would have helped remove the salt from your system without the rise in blood pressure and without the increased risk of cardiovascular disease.
To keep blood pressure stable, and to keep the swelling away, salt and potassium need to be kept in balance.
Providing the Energy for Transport
Earlier we said that we invest 20-40% of our energy at rest in keeping salt outside of cells and potassium inside cells. This requires energy because the laws of physics state that everything in the universe tends to randomly spread out and mix together. Reversing this law by keeping everything in one place requires energy, just like jumping in the air requires energy because it fights against the law of gravity.
This creates a situation where there is so much sodium on the outside that it just wants to bust right in with all its might, and so much potassium on the inside that it wants to bust right out with all its might. They want to do this to comply with the laws of physics that everything spreads apart and mixes together, much like anything high up wants to drop down to the earth to fulfill the law of gravity.
That hunger to cross to the other side is a form of energy, and it can be used to fuel the transport of many other things from outside the cell to inside, or vice versa.
For the most part, it is sodium that is used for transport, but occasionally potassium, chloride, or both, can be found assisting sodium or even being used on their own to help transport something.
Digestion and Nutrient Absorption
The transport function of sodium gives it a central role in the digestion and absorption of nutrients.
Once we so much as see or smell the food we are about to eat, we start making saliva. Sodium helps transport saliva from our salivary glands into our mouth.
We chew the food, swallow it, and then it hits our stomach. Our stomach makes hydrochloric acid to start breaking down protein in the food, and to start separating important vitamins from those proteins so they can be absorbed later on in the intestines. Hydrochloric acid contains chloride, and sodium is used to transport it into the stomach. Thus, both components of salt -- sodium and chloride -- are key to digestion in the stomach.
After the stomach comes our small intestine. This is where we absorb most of our nutrients.
Sodium is used to transport digestive juices and bile acids into the small intestine. The digestive juices contain the enzymes that will break down our food. The bile acids will be used to absorb fats, cholesterol, and the fat-soluble vitamins, which are vitamins A, D, E, and K.
Sodium is also used directly to absorb glucose, the main carbohydrate, and most amino acids, which are the breakdown products of the protein found most abundantly in meat, poultry, fish, eggs, dairy, and beans.
Finally, sodium is also used directly to absorb the following vitamins and minerals:
Vitamin C
Pantothenic acid (vitamin B5)
Biotin (vitamin B7)
Sulfate
Some forms of selenium
Phosphorus
Magnesium
Iodide
Nutrient Retention and Transport Within the Body
Once the nutrients are absorbed, sodium is used in the kidney to prevent them from being peed out, and is very often used to transport these nutrients into our cells so they can be used.
Sodium is used to transport many other substances, such as hormones, drugs, toxins, and many substances essential for life that we make and transport throughout the body every day.
For example, sodium is used to transport creatine, which athletes use for strength and big muscles, but which has also been shown to help with depression in women, and is known to provide the fuel needed to produce stomach acid, maintain healthy skin, heal wounds, process light inside our eyes, and power sperm to swim up the vaginal canal when searching for their egg.
Sodium and chloride are also both used to control the level of acidity (that is, the pH) in the body. They are needed to remove acids into the urine, to retain bicarbonate in the body, which is alkaline, and to control the pH of different tissues or even different compartments within cells to optimize them for specific functions.
Salt and Potassium in the Nervous System
Neurons, the main cells our brain is made of, and the cells that help us perceive with our senses and control our movements, communicate largely using salt and potassium.
Just as in other cells, salt is pumped to the outside of neurons and potassium to the inside. That hunger that drives them to reach the opposite side, just as it’s used for transport elsewhere, is used in neurons as a signal to flip them on or off. Neurotransmitters activate them usually by flipping open sodium channels, allowing sodium to rush through to the inside of the cell. Neurotransmitters inhibit neurons usually by flipping open chloride channels, allowing chloride to rush through to the inside.
Once a neuron is activated, it sends a signal to another neuron or to a muscle cell by opening and closing a series of sodium and potassium channels that run along its length, allowing sodium to rush in and potassium to rush out. Their movement acts as the signal that travels down to the end of the cell and causes it to take some action, usually releasing a neurotransmitter onto the nearby neuron or muscle cell.
The transport function of these minerals is just as important in the nervous system as it is elsewhere. Sodium is used to clear most of the major neurotransmitters back into the neurons they came from, or into nearby assistant cells, to prevent those neurotransmitters from having an effect for longer than intended. In some cases, potassium and chloride cooperate with sodium to remove the neurotransmitters.
A deficiency of salt or potassium in the brain could disrupt the ability of a neuron to send and receive signals, and it could also make neurons hypersensitive to neurotransmitters that aren’t being cleared effectively.
For example, some people with glutamate sensitivity have negative reactions to MSG or to the natural glutamate in protein-containing foods that have been fermented, slowly cooked, or pressure cooked. Glutamate is a neurotransmitter that is cleared using sodium and potassium. Perhaps a deficiency of salt or potassium could play a role in this sensitivity by making it more difficult to clear the glutamate.
Potassium Activates Enzymes
There are hundreds of enzymes that depend on a certain amount of salt and potassium being present in their environment to have optimal activity. A much smaller number are activated by directly binding to one of these minerals.
In the case of sodium, only one enzyme has been established as sodium-dependent in humans. It is involved in breaking down collagen. Perhaps it helps keep our skin looking fresh by helping us replace old collagen with new collagen.
The number is larger for potassium. Potassium directly activates a number of enzymes that have the following functions:
Enabling decision-making about whether glucose should be broken down for energy, used to stoke the metabolic flame in which all fuel is burned, or conserved while protein is made into extra glucose.
Burning glucose for energy.
Burning ketones for energy.
DNA repair.
Incorporation of selenium into proteins so it can act as an antioxidant and can activate thyroid hormone, which raises the metabolic rate (see the lesson on iodine for a more complete view of thyroid hormone).
Synthesizing niacin (vitamin B3) from protein, and activating the niacin found in plant foods (niacin from animal foods does not require this process).
Preventing the production of unnecessary proteins, which would waste energy or activate inappropriate metabolic pathways.
Coordinating gene expression during the fasting state to break down unneeded proteins and damaged tissue.
From this wide array of roles, we can imagine that insufficient potassium could make energy metabolism go haywire and could hurt our ability to protect our tissues from damage and repair damage as we age.
Osteoporosis and Kidney Stones
A small number of studies have suggested that extra sodium causes our bones to release calcium, while potassium has the opposite effect. This could contribute to osteopenia and osteoporosis, conditions of low bone mineral density. These studies have also suggested that this calcium winds up in the urine, and on its way there it passes through the kidney, where it could contribute to kidney stones.
While the evidence isn’t very strong, to the extent it may be true, it suggests that sodium and potassium need to be balanced to support bone health and kidney health the same way they need to be balanced to support stable blood pressure and minimize swelling.
In the next lesson, we will cover how to meet the requirements for salt and potassium while also keeping them balanced in just this way. We will also cover drugs, diseases, and lifestyle choices that could cause dangerous disturbances in the blood levels of these minerals.
Wrapping Up
But first, let’s wrap up part 1!
Salt and potassium are hydrating. Rather than drinking plain water between meals, put a tiny pinch of salt and a little bit of lemon juice in your water, or have small amounts of water with food.
Without adequate potassium, salt could leave your cells dehydrated, raise your blood pressure, and increase swelling.
Salt is extremely important to the digestive process, from releasing saliva, stomach acid, and bile acids, to directly absorbing glucose, amino acids, and many vitamins and minerals.
Salt is involved in retaining nutrients, transporting them into cells and between tissues, and in transporting many other essential substances, such as creatine.
Salt is important to controlling the proper level of acidity in the body as a whole and in individual tissues and compartments within cells.
Salt and potassium allow neurons to respond to neurotransmitters or other signals, and to transmit signals to other neurons or to muscle cells.
Salt and potassium clear neurotransmitters, preventing them from having more of an effect than intended. Lack of these minerals in the brain could contribute to glutamate sensitivity.
Potassium activates a number of enzymes involved in energy metabolism, antioxidant defense, and repair.
Although the evidence is weaker than it is for blood pressure, balancing salt with potassium may be important to bone health and kidney health as well.
Originally Posted by thebear
Salt is made of two minerals, sodium and chloride.
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