Why a low salt diet could actually be bad for you

Four salt shakers in a row with decreasing amounts of salt inside
Key points
  • Traditional recommendations on salt intake are based on dietary guidelines from 1977
  • The same guidelines told us that “eating fat makes you fat”, which has since been disproven
  • Many high sodium foods are unhealthy because they are high carb, highly processed foods
  • High carb and low potassium intake are major causes of high blood pressure
  • Low salt intake can increase insulin resistance – your body needs sodium to store glucose
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Salt has been misunderstood for over 40 years

In 1977 George McGovern, then Chairman of the United States Senate Select Committee on Nutrition and Human Needs, presented the Dietary Goals, a series of guidelines on what foods Americans were recommended to avoid excess intake. These guidelines popularized the idea that high salt is unhealthy, and this recommendation was based on a paper that said salt could be just one factor in high blood pressure. The same guidelines also popularized the mistaken idea that “eating fat makes you fat”, which has since been soundly disproven.
As chronicled in Dr. James DiNicolantonio’s book “The Salt Fix,” only one year early, G. Meneely and H. Bartabee had published a paper entitled “High Sodium-Low Potassium Environment and Hypertension”. Somehow McGovern and his fellow committee members missed the key findings of Meneely and Battarbee’s research – high salt could cause hypertension if it was paired with low potassium and this was the case in people who were genetically susceptible. Nonetheless, the 1977 Dietary Goals recommended that all Americans restrict their salt intake to just 3,000 milligrams per day. I don’t think things would have gone well for McGovern had he presented these guidelines to the salted-fish-loving Romans of the second century A.D.

The disagreement on our historical diet

Certain estimates say that our ancestors were getting less than 1,500 milligrams of sodium per day. This idea seems to come from a 1985 paper in the New England Journal of Medicine, where authors estimated that intake of sodium was just 700 milligrams per day in the Paleolithic Era. However, this was based on the sodium content of selected plants and the muscle meat of selected land animals. Dr. James DiNicolantonio explains that what wasn’t taken into account was that our ancestors didn’t waste much of the animal, they consumed the salty skin, even the salty blood and got sodium from the interstitial fluid. 
The work of researchers like Loren Cordain and fossil isotope analyses suggest that most hunter gatherers got around 56-65% of their nutrition from animal foods. So, we should expect similar consumption from the Paleolithic man or woman. So not everyone agrees with the idea that we used to get so little salt.
Spoon containing salt with salt spilled on the ground

Historically, some people ate 20 times the modern recommended salt intake per day

If humans adapted to a salt-deficient environment, we should expect that the body tends to hold onto salt. The body is indeed very good at holding onto salt.  However, healthy people are perfectly capable of excreting too much salt. Mark Kurlansky’s book “Salt: A World History” explains that the salt intake in Europe from at least the 1500’s onward used to be very high. People got as much as 40g to 100g per day, thanks to using salt to preserve fish. That amount is the equivalent of consuming the entire contents of one to two 2oz salt shakers like you’d see in a diner. What happens to all that extra salt? Thanks to your kidneys, you just pee it out. A paper from the journal Hypertension found that people can excrete ten times the “normal” salt intake, up to 86 grams of salt per day.  
Of course, this is not to say that our ancestors were necessarily healthier than us, and for the most part they had much lower life expectancy. The key point is that low salt intake has not always been seen as the norm. The one thing we do know for sure is that they didn’t have easy access to large amounts of highly processed food.

Correlation is not the same as causation

It may seem like there are a lot of examples of reducing salt having a good effect in certain populations. But think about it this way:
  • Processed foods are loaded with tons of stuff we don’t need and also happen to be loaded with sodium 
  • Processed foods are generally not a reliable source of potassium 
  • Processed foods are often packed with refined carbohydrates and of course sugar

When people are put on a low-sodium diet, they typically reduce intake of high-carb processed foods which happen to be rich in sodium. That in itself is already a win for your health, but you’re going to have to replace those processed foods with whole foods like vegetables, which have plenty of potassium – another win. 

So is it the low sodium that’s helping your health, or is it the reduction in low quality food? Good luck finding a study showing that sodium has ill effects on a group of people eating a whole foods, high potassium, low sugar, low refined carb diet.

A bad combo: High carb, low salt

In 2014 Dr. James DiNicolantonio published a paper in the Open Heart cardiology journal entitled “The wrong white crystals: Not salt but sugar as aetiological in hypertension and cardiometabolic disease”. In the paper he explains why it could be dangerous if the sodium content of processed foods was reduced, because it could give people the impression that such processed foods are a “healthy” part of a low-sodium diet, and so cause them to eat even more of them. Of course, the ideal is to eat zero processed foods or junk food, but let’s consider this high refined carb, low sodium, low potassium scenario. 
When you have low sodium intake, your body does what it can to retain the sodium that it has. Low sodium prompts the body to release the hormones aldosterone and insulin, which both tell the kidneys to hold onto sodium. Insulin is the hormone used to get carbohydrate into your muscle, fat and liver cells, so when you have high blood sugar, your pancreas release a lot of insulin. Too much insulin release can lead to insulin resistance, and in turn to diabetes. You can think of insulin resistance like a form of drug resistance, with the insulin not “working” as well. It can’t get the carbohydrate into the cells like it used to be able to. This is why diabetics inject themselves with extra insulin – to take the carbs in the blood (blood sugar) and cram it into the cells for energy.    
However, low salt can worsen insulin resistance. In fact, a study looking at just seven days on a low salt diet found that participants had worsened insulin resistance. One reason for this is that one of the transporters that gets carbs into our cells (known as a “sodium-glucose cotransporter“) is dependent on sodium, so having a low sodium intake can make it harder for your body to store glucose in cells despite releasing insulin. A high carb, low salt diet is particularly bad for diabetics who already have trouble using carbs for energy 

Another bad combo: High carb, low potassium

Like sodium, potassium plays an important role in carbohydrate metabolism. It does this in two ways.
Firstly, the “sodium-glucose cotransporter” mentioned above (which drives carbs into the cells) is dependent on the proper functioning of the sodium-potassium pump, which moves sodium and potassium in and out of your cells. With lower potassium intake the speed of the sodium-potassium pump is decreased, and therefore the speed of sodium-glucose cotransport is also lower. That can mean it takes longer for your blood sugar levels to decrease after a meal, and therefore more insulin secretion, which in turn promotes insulin resistance. 
A second way that potassium affects carbohydrate metabolism is by regulating insulin secretion. Low potassium intake can make the cells which secrete insulin less sensitive to glucose, which again means your blood sugar levels staying higher for longer.
You may also have heard of “metabolic syndrome“. If you have metabolic syndrome, it means you have a number of risk factors that increase your chance of developing heart disease, stroke, and diabetes. One of these risk factors is insulin resistance. Low potassium intake has been found to be associated with metabolic syndrome. That’s not to say having low potassium intake will make you fat, but a diet low in potassium is typically low in whole foods and satiating fiber, and so can lead to such conditions.

Even worse: High carb, low salt, low potassium

Going by the above, it goes without saying that high carb with low salt and low potassium is even worse than just low salt or low potassium. High carb means high insulin secretion. Low salt means makes it harder for that insulin to do its job without enough sodium to help glucose into the cells. Low potassium makes it harder for the little sodium that’s available to help that glucose on its way, and harder for your body to secrete enough insulin.
You might be wondering why I’m talking about blood sugar so much if salt is supposed to be the thing that causes high blood pressure. Salt was thought to be the issue because water follows sodium. When you have too much sodium in the blood, water follows the sodium into the blood vessels, which increases the blood volume and blood pressure. That makes sense – if you have two identical tubes filled with water but one has more water in it, that one will have more water pressure. However, remember how our bodies excrete excess salt when needed, even if we eat a ton of it? Well, as we just saw, insulin interferes and encourages the kidneys to have us retain salt. So, it’s not so much the salt that’s giving people hypertension, it’s the high blood sugar causing large amounts of insulin to hold the salt there. High carb intake makes it harder for the body to compensate for high sodium intake.
Now you’re saying “Hold on a minute, you just said low potassium causes ‘not enough insulin’ to be secreted!” How right you are! The thing is, high insulin is bad, but unregulated high blood sugar is arguably much worse. Excess blood sugar floats around in the blood stream and damages small blood vessels, particularly in the feet and eyes, which can lead to blindness. Too high blood sugar for too long is toxic. 
The sky-high levels of insulin that accompany diabetes are bad, but they are at least protecting your body from the danger of high blood sugar. You know what else high blood sugar damages? Your kidneys. You know what regulates things like sodium for you so you don’t get high blood pressure? Yup, your kidneys!

The body’s intricate sodium and potassium balancing act 

As highlighted earlier, there are different views on how much salt humans used to get relative to potassium. Regardless, it doesn’t change the fact that our bodies want sodium and potassium to be in balance. The body reacts in a certain way that affects both potassium and sodium when we don’t get enough salt. When you’re low on sodium – when you’ve sweated too much, when your diet is too low in salt or possibly when you chug too much water – the hormone aldosterone is secreted. One function of this hormone is to preserve salt. Conversely, when potassium intake is low your body reduces secretion of aldosterone. However, if your carb intake is high insulin secretion will also be high, which means sodium retention – that can make it harder for your body to restore balance.
High levels of potassium also trigger secretion of aldosterone. Potassium is good, but you can have too much of it – that’s called hyperkalemia. Luckily, our bodies excrete potassium when we have too much of it, thanks to aldosterone being secreted. But wait a minute…aldosterone is also secreted when you have too little salt. This is because, potassium and sodium need to be in balance. When levels of sodium get too low, the body not only retains sodium, but secretes potassium to balance these two. Studies in humans have found that people on a low salt diet secrete roughly twice as much potassium. You want to have enough potassium in your body, but if you don’t have enough salt, you can’t maintain that potassium as well. 

Furthermore, high excretion of aldosterone itself is associated with high blood sugar and obesity, hypertension, heart disease and metabolic syndrome. Ironically, the very hormone which is secreted in response to low sodium is in fact associated with high blood pressure! 

Chocolates and coffee balancing on each side of a fork

It’s not about “good” and “bad” minerals or nutrients, it’s about balance

There are so many things in the body that must be in balance. Have you been getting your Omega-3’s from fish oil supplements recently? Fish oil / Omega-3 / DHA-EPA supplements seem to be the most popular supplement, according to the NIH. Omega-3’s are great, but they need to be in balance with Omega-6’s. Omega-6 fatty acids support the inflammatory processes in your body. Omega-3 fatty acids support anti-inflammatory processes in the body. Thanks to vegetable oils, people are getting far too much Omega-6. It’s thought that the optimal Omega-6 to Omega-3 ratio is 1:1, but the typical western diet is at 16:1. So, it makes sense to load up on Omega-3’s, hence the boom in these supplements. 
However, so many other things in the body need to be in balance. Zinc needs to be in balance with copper. Vitamin A and Vitamin D need to be in balance. Even two amino acids – methionine and glycine – should be in balance. Sodium and carbs are no different. Sodium needs to be balanced with potassium, and carbs need to be balanced with your body’s energy needs.
In conclusion
Lessons learned
Before this gets anymore complicated, the key takeaways here are that:
  • Lower salt is not always better
  • Focus on getting enough potassium, rather than eating less salt
  • Stay away from processed foods
  • Keep your carb and sugar intake in check
  • Think more about keeping your nutrients in balance, rather than restricting intake

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