A Recent Paper in The Lancet, a Prestigious British Medical Journal, Shows Quite Clearly That Low Salt Intake Is More Dangerous Than High Intake

For decades, a staple piece of advice from most doctors has been “eat less salt—reduce sodium.” Anyone with a rudimentary knowledge of how the body regulates sodium (salt) would take such advice with a grain of it. Reducing sodium will reduce blood pressure by maybe 3 mg-Hg. OK, every bit counts, but this is not enough of a blood pressure reduction to make much of a difference.

Sodium levels are controlled by the kidneys. The level is important. Normal is 135-145 mmol/L. A 10% deviation up or down from this is considered severe, and a 20% deviation could be life threatening.

So, as usual, the level is tightly regulated by the hypothalamus, a tiny brain that seems to have a hand in almost every key bodily function. The hypothalamus will order the kidneys to dump sodium if it is too high and conserve it is it is too low. However, if a person is dehydrated, this may be impossible, and that, not dietary excess, is the usual cause of high sodium in the blood (hypernatremia). So drink a lot of water.

If, and this is a fairly big if, a person’s kidneys are functioning properly, excess sodium is unlikely to be any problem. The kidneys will simply excrete it into the urine.

But what if there is a shortage of sodium? Unlike calcium, the body has no store of salt it can tap. It all has to come from food. Real food, anyway. Many industrial food items, like cereals, will remove the natural sodium and proudly proclaim “heart healthy—low salt.” The body will work furiously to keep the sodium levels in a safe range. If they are too low, the body can dump water. However, this too has its limits. Low sodium levels can cause nausea, headache, dizziness, short-term memory issues, fatigue, muscle spasms, and possibly even a coma. Doesn’t sound like something that should be tampered with does it? But, of course, the low salt craze does exactly this.

What if the Kidneys Aren’t Normal?

People with heart disease almost always have some degree of kidney impairment. The usual heart disease, atherosclerosis, is often called clogged arteries, and they tend to be clogged everywhere. The kidneys are essentially an elaborate arrangement of arteries and veins (deep dive found here), so the atherosclerosis will have effects on the kidney. Impaired function will mean impaired regulation, so it would be important to worry a bit about sodium intake. Not too much, not too little. Does a person in this situation need to adjust? The sodium level is almost always measured in the annual-physical blood test. If the level is 135-145, stay the course. Otherwise you could adjust. If it tends high, you might start by drinking more water.

The Actual Results from The Lancet Paper.

The Paper, link here, is quite interesting. It found that excess salt users with high blood pressure (and therefore heart disease and kidney impairment) had 23% more heart attacks than those taking normal amounts of salt. But, the high-blood-pressure group that had low salt intake, less than 3 grams, had a whopping 34% increase in heart attacks. For people with normal blood pressure, high salt consumption caused no problems, but low consumption cause a 23% increase in heart attacks.

The US government recommendation of 2.3 grams is actually lower than 3 grams where The Lancet study started seeing increased heart attacks. Clearly, the recommended salt level should be revised. We will start the meter and see how long it takes.

The Lancet and the authors have been heavily criticized for the paper, largely on the basis of methodology and also direct ad hominem attack. In fact, no one seems to be disputing the dangers of low sodium. It’s mainly defense of a sacred cow. Or their own skin. If I were advised to lower my salt intake even though I had normal blood pressure, and had gotten a heart attack because of it, I would not be very thrilled. Toppling sacred cows is a tricky business.

So How Much Salt?

Two or three teaspoons of salt a day probably represents the lowest risk amount for all people. Not too much, not too little. Some of this daily amount will be found in the food you eat, especially fish, meat, and some plants. There is no need to bother with bland low-salt food. The amount of salt in real food is about right. Add a bit for flavor. Industrial food is a different story. Much of this food has a lot of added salt. Best practice: completely avoid this food. It is bad for you in countless ways.

If a doctor advises you to lower your salt intake, you might want to ask him to show you blood test numbers that indicate high circulating sodium. If it ain’t broke, don’t fix it.