The truth about salt

Sprinkled salt on dark background with broken heart shape made from salt.

By 1982, salt was called ‘A New Villain’ on the cover of TIME magazine. The 1988 publication of the INTERSALT study seemed to seal the deal. This massive study involved 52 centers in 32 countries and laboriously measured salt intake and compared this to blood pressure. Across all populations, the higher the salt consumption, the higher the blood pressure. Seemed like a slam dunk, although the effect was quite small. A 59% reduction in sodium intake would be predicted to lower the blood pressure by only 2 mmHG. If your systolic blood pressure was 140, severely restricting your salt could lower that to 138.

However, no data existed as to whether this would translate into less heart attacks and strokes. But based on this influential study, in 1994 the mandatory Nutrition Facts Label proclaimed that Americans should only eat 2,400 mg per day (about one teaspoon of salt). Yet the stubborn fact remains that virtually every healthy population in the world eats salt at levels far above that recommendation. The dramatic improvements in health and lifespan of the last 50 years have occurred during a period where almost everybody was considered to be eating too much salt.

Starch structure

Our belief in the benefits of low salt consumption are largely based on mis-information and myth-information. The underlying assumption of the salt reduction advice is that eating too much salt is a recent phenomenon brought on by the increased consumption of processed foods. Dahl, for example, claimed in his writings that widespread use of salt as a condiment was uncommon until modern times.

Data from military archives going back to the war of 1812 show that soldiers and presumable the rest of Western society ate between 16 and 20 grams of salt per day. During the war of 1812, soldiers maintained a daily consumption of 18g/ day despite high cost. American prisoners of war complained bitterly that their 9 g/day of salt was ‘scanty and meager’. It was only after World War II, when refrigeration replaced salting as the primary means of preserving food that Americans lowered their average salt intake to 9g/ day where it has remained since. During that period pre-WWII, there was no concern of excess deaths from heart disease, stroke or kidney disease – the main things used to scare us into lowering our salt intake.

The tides turn

From its very inception, there were problems with the hypothesis that lowering salt could save lives. Dahl failed to notice all the various high-salt eating cultures that had no adverse health consequences. The Samburu warriors, consume close to two teaspoons of salt per day even going as far as eating salt directly from the salt licks meant for their cattle. Despite eating all this salt, the average blood pressure is just 106/72 mmHg and does not rise with age. In comparison, about one-third of the adult population in America is hypertensive with a blood pressure of at least 140/90 mmHg or higher. For reference, a normal blood pressure is less than 120/80 mmHg and generally rises with age in the United States. Villagers from Kotyang, Nepal, eat two teaspoons of salt per day, and the Kuna Indians eat one and a half teaspoons of salt per day, with no hypertension words, clearly contradicting Dahl’s hypothesis that a high-salt diet causes hypertension.

Salt diagram 1

The most recent survey of global salt intake shows that no area of the world conformed to either the AHA or the WHO recommendations for salt restriction. The central Asian region had the highest salt intake, followed closely by high income Asia Pacific region including Japan and Singapore. The Japanese diet is notoriously high in sodium with copious use of soy sauce, miso and pickled vegetables. The Japanese themselves seem to suffer no ill effect as they have the world’s longest life expectancy at 83.7 years. Singapore is third in life expectancy at 83.1 years. If eating salt was really so bad for health, how could the world’s longest lived people also eat one of the world’s saltiest diets?

The concerns of a low salt diet started in 1973, when an analysis found six where the average blood pressure was low despite a high-salt diet. For example, the Okayuma, consumed more salt than most nations today (up to 3 1/3 tsp per day), and yet had some of the lowest average blood pressures in the world.

In some cases, blood pressure actually decreased as salt intake increased. For example, North Indians consumed an average salt intake of 2 ½ tsp per day (14 grams) but maintained a normal blood pressure of 133/81 mmHg. In South India, average salt intake was about half that of North India, but the average blood pressure was significantly higher at 141/88 mmHg.

Conflicting evidence

But there was still the question of the massive INTERSALT study. Further analysis of the data began to paint a significantly different picture of salt. Four primitive populations (the Yanomamo, Xingu, the Papua New Guinean, and the Kenyan) had been included in the initial analysis, which had significantly lower sodium intakes than the rest of the world. They lived a vastly different, primitive lifestyle from the others, and one had a sodium intake 99% lower than the rest. These outliers had limited generalizability to the rest of the world and because they were such outliers, had an outsized effect on the averages.

Salt diagram 2

These 4 primitive societies differed from modern ones in far more than just diet. For example, the Yanomamo Indians of Brazil still live traditionally, hunting and gathering just as they had done centuries ago. They practice endocannibalism, where the ashes of loved ones are consumed because they believe it keeps them alive. There are no processed foods. There is no modern medicine. Comparing this tribe living in the forests of the Amazon to a modern American in the forests of New York is hardly fair. Isolating a single component of their diet, sodium and proclaiming it to be solely responsible for high blood pressure is the height of bad research. It is no different than concluding that wearing loincloths lowers your blood pressure.

There were other issues, too. Two populations (Yanomamo and Xingu Indians), when studied further, had the near absence of a specific gene D/D of the angiotensin converting enzyme, which put these populations at extremely low risk of heart disease and hypertension. Thus, low sodium intake may not be the major or even minor contributor to low blood pressure in these groups.

In this case, more information can be gained by removing these outliers from the study populations and seeing if the original salt hypothesis holds true. When those four primitive populations were removed and forty-eight Westernized populations were left in the study, the results were completely opposite the original findings. Blood pressure actually decreased as salt intake increased. Eating less salt was not healthy, it was harmful.
Starch structure
The evidence from the United States was not encouraging either. The National Health and Nutrition Examination Survey (NHANES) are large-scale surveys of American dietary habits carried out periodically. The first survey found that those eating the least salt died at a rate 18% higher than those eating the most salt. This was a highly significant, and disturbing result.

The second NHANES survey confirmed that a low salt diet was associated with a staggering 15.4% increased risk of death. Other trials found an increased risk of heart attacks of eating a low salt diet in treated hypertensive patients. Those were precisely the patients doctors had been recommending a low salt diet!

In 2003, worried, the Center for Disease Control, part of the US Department of Health and Human Services asked the Institute of Medicine (IOM) to take a fresh look at the available evidence focusing not on blood pressure, but mortality and heart disease.

After an exhaustive search of the medical literature, the IOM made several major conclusions. Although low salt diets could lower blood pressure, “Existing evidence, however, does not support either a positive or negative effect of lowering sodium intake to <2300 mg/d in terms of cardiovascular risk or mortality in the general population.”. That is, lowering the salt intake did not reduce the risk of heart attack or death. However, in heart failure, “The committee concluded that there is sufficient evidence to suggest a negative effect of low sodium intakes”. Oh my. The very patients we were most strenuously recommending to reduce their salt would be harmed the most. But dogma is hard to change. The 2015 Dietary Guidelines continues to recommend reducing sodium intake to less than 2,300 mg of sodium (about one teaspoon of salt) per day with a recommendation of no more than 1,500 mg of sodium (about two-thirds of a teaspoon of salt) per day in hypertensives, blacks, and middle-aged and older adults.

Why is salt restriction dangerous?

Salt is crucial to maintain an adequate blood volume and blood pressure ensuring that our tissues are perfused with the oxygen carrying blood and nutrients. Salt is composed of equal parts sodium and chloride. When we measure the electrolytes in the blood, salt (sodium and chloride) are by far and away the most common ions. For example, normal blood will contain sodium at a concentration of approximately 140 mmol/L, and chloride at 100 mmol/L, compared to potassium at 4 mmol/L and calcium at 2.2 mmol/L. No wonder we need salt so badly.

There is speculation as to the evolutionary reasons why our blood evolved to be mostly salt. Some believe that we evolved from single celled organisms in the ancient seas of the Earth. As we developed multicellularity and moved onto land, we needed to carry some of the ocean with us as ‘salt water’ inside our veins and hence salt comprises the vast majority of the electrolytes of the blood. Salt is vital, not a villain.


Dr. Jason Fung

Dr. Fung’s top posts

  1. How to renew your body: Fasting and autophagy
  2. Longer fasting regimens – 24 hours or more
  3. The truth about salt

Type 2 diabetes

Weight loss

Keto

Intermittent fasting

 

More with Dr. Fung

All posts by Dr. Fung

Dr. Fung has his own blog at idmprogram.com. He is also active on Twitter.

The Obesity CodeThe Complete Guide to Fastingthe-diabetes-code (1)

Dr. Fung’s books The Obesity Code, The Complete Guide to Fasting and The Diabetes Code are available on Amazon.

15 comments

  1. Greg
    How about a person like myself with. CHF. And a 20 percent heart eject.
  2. David
    Why does a salty meal make my heart pound? To the point that I will wake up in the middle of the night thinking I'm about to stroke out from explosively-high BP? Salt and caffeine cause this repeatably.
  3. Jennifer
    Why aren't any references cited? Any MD should know that an article is useless without citing sources.
  4. Sue
    Excellent article thank you. I feel a lot better since I stopped worrying about amounts of salt and eat the amount that feels right with each meal. 'Carry some of the ocean with us' - a lovely summary.
  5. Dr. Dean Raffelock
    Between 25- 30% of Americans have enzymes that make them overly sensitive to high sodium intake and this can significantly raise their blood pressure. Very high blood can definitely cause strokes. These people need to limit their salt intake to somewhere around 2000- 2500 mg. Per day. On the other hand, People with low pressure can benefit from a higher salt diet. Most people can tolerate and benefit from approximately 3000- 6000 mg of salt per day providing they also have a diet with at least that mount of potassium. Otherwise a high salt low potassium diet will make red blood cells become too rigid and adversely affect their natural sponge-like consistency which allows them to be squeezed through capillaries and reach their target tissues. Be cautious about anyone who claims to be an authority in this issue who doesn’t have a balanced point of view.
  6. Una
    Not much to back it up either way! Need more evidence.
  7. Paul Pancoe
    No mention of the Sodium to Potassium ratio?
  8. Jos
    Is sea salt or Himalaya salt better for health then refined salt from a factory?
  9. Karen
    I believe in avoiding processed foods, that's where the unneeded extra salt comes from. But salt your whole foods to taste and enjoy. I also read once that refrigeration, and thus the need to salt and cure meats, reduced the incidence of stomach cancer significantly and that the Japanese still have a higher rate of this.
  10. Theroigne
    I looked and looked for cold cuts ie sliced deli meats without additives, and the only one that I have been able to find is Prosciutto (Parma ham). The traditionally made stuff has just two ingredients, pork legs and salt. Any pack with the gold crown, in Europe, is the real deal. I don't like stock cubes or stock pots which list salt as a major ingredient, as it's a cheapskate move by the manufacturer. Also, I want to control the taste as much as poss. As a college-trained chef, I was taught that you never put salt in a stock and you leave it to the customer to add salt to their food if they wish. Like Karen, I add the amount of salt that I want. I love it on eggs. I use both sea salt and Himalayan pink salt. Whether they are healthier or not depends on the additives I guess. Some manufacturers add stuff to keep the salt free-flowing and in some countries they are required to iodise it.
  11. Suzanne Hickman
    What can I do to fight very high inflammation numbers? My blood test showed a number of 43 when it should be less than 1.
  12. Mark
    Would like to hear what Dr. Fung has to say in regards Dr. Dean Raffelocks comments; especially his comment about 25-30% of people having a higher sensitivity to Sodium. If this is true, what are the proper guidelines for these people? Furthermore, how does one even know if they fall into this category? Hope to see a reply and thank you.
  13. V. MacBean
    Loved reading the oh-so-sensible (Read More) article on salt: so balanced, sensible, and rational. Thank you.
  14. Linda
    I believed and followed the low salt message for many years. I read 'The Salt Fix' by James DiNicolatonio and concluded I had gone too far and needed more salt. I was borderline CKD (GfR at about 60) but no other markers for kidney disease and normal BP, for several years. After increasing salt intake, my GfR has gone up to 70, my nighttime leg cramps have gone, BP still normal....and my food tastes better!
  15. Shigetada
    It was an interesting article that raised one question; i.e. it may not be right to compare national average of salt consumption.

    I was born and raised in Japan which is described in the article →"Because of world's longest life expectancy, Japanese don't seem to suffer from notoriously high sodium diet".

    The sodium consumption in Japan varies largely depending on areas; and people in some areas consume twice or three times more than others. I remember there are a number of statistics that shows significantly more people suffer from stroke in higher sodium consumption areas.

    Another interesting statistics is those areas where they grow apples have significantly less stroke. I assume it is because of higher potassium consumption from apples.

    Since we are all unique, statistics should be considered only as a tendency or basic guide line, and each individual is responsible in finding own body reaction.

Leave a reply

Reply to comment #0 by

Older posts