For the good of your heart: Keep holding the salt

Naomi D. L. Fisher, MD
Naomi D. L. Fisher, MD, Contributor

Your doctor has probably told you to cut back on salt, especially if you have high blood pressure. For years we’ve understood that excess salt raises blood pressure and increases deaths from heart disease. The guilty element is sodium, which pairs with chloride to form common salt. So when the journal Lancet recently published a study reporting that low dietary sodium was associated with an increased risk of heart disease and death, controversy was predictable.

A wealth of rigorous scientific studies supports a link between excess sodium intake and high blood pressure, heart attacks, and strokes. Yet the Lancet paper reported that people who consumed both high sodium and low sodium diets were more likely to suffer from cardiovascular disease and death. They concluded that a “moderate” intake of 4-5 grams of sodium daily was the best goal. To put this into perspective, the Food and Drug Administration (FDA) has set an upper limit of 2.3 grams (2,300 mg) daily for most Americans, while the American Heart Association recommends even less, limiting sodium to 1.5 grams (1,500 mg) daily for most people. The average American diet, considered much too high in sodium, contains around 4 grams of sodium.

It’s frustrating to read studies that seem to contradict dogma. They can undermine our faith in science altogether. Therefore, we must carefully analyze all study details to learn whether new science is being discovered, or whether bad science is being reported. And in the case of the sodium story, most experts and an enormous body of evidence support the conclusion that the recent study is flawed.

Studies that measure sodium intake use different methods. The gold-standard, with the highest level of scientific rigor, would be a randomized-controlled trial. That would mean half of a large population eats a high sodium diet and half eats a low sodium diet. Every single food item consumed over weeks, months and years would have to be measured for sodium content. Plus, no one would know which group they were in. Obviously this is not just impractical, it is impossible. So we look for short-cuts, and for indirect measures of dietary sodium.

The best available method for large groups is to measure urinary sodium as a substitute for dietary sodium. Instead of measuring what goes in, we measure what comes out. But the dietary sodium intake of most people is not at all constant. It has wide swings, ranging from very low to extremely high, depending on what we eat on a given day. And therefore the sodium in urine also fluctuates wildly.

The best way to deal with this reality is to collect urine for 24 hours on multiple days, over extended periods of time. Here’s where the problems start with the Lancet study. It did not examine multiple 24-hour urine collections, but rather one single urine collection on only one day from each participant. This resulted in a poor estimation of everyone’s daily intake of sodium.

Another major flaw resulted from a bias called “reverse causality.” It means that the high risk of death wasn’t caused by low sodium intake. Instead, the relationship was backwards. Participants in the Lancet paper were not healthy volunteers, but were enrolled specifically because they were at risk for or diagnosed with conditions like high blood pressure and diabetes. It was precisely because of their diagnoses and overall health that they may well have eaten less sodium (and less food overall).

Evidence from well-performed studies and public health strategies clearly shows that sodium reduction prevents cardiovascular disease. Recommending up to 5 grams of sodium daily would result in tens of thousands of more deaths annually. If you are interested in a rigorous rebuttal of the Lancet report, see the Sounding Board published by the New England Journal of Medicine.

Debates are healthy, but this one should not distract us from the reality that only a tiny fraction of our population eats a low sodium diet. Most of us are eating far too much sodium. It may well be that low sodium diets are harmful for small subsets of people, but for the majority it will take more convincing evidence to change current efforts at salt restriction.

You may not realize that most of the sodium we eat comes from processed foods — not from our salt shaker. This fact makes it even more difficult to cut back, because so many foods we buy are loaded with salt.

Public efforts to reduce sodium intake in America are underway. In fact, the FDA just recommended voluntary sodium reduction targets for the food industry. We are lagging behind other countries like the United Kingdom and Japan, which have set targets for sodium in processed foods and seen falls in blood pressure and deaths from stroke and heart disease.

Reducing sodium in our diets is a health strategy proven to prevent heart attacks and strokes. By paying attention to the sodium in our diet, we can take one more step towards controlling our own health.

Related Information: Controlling Your Blood Pressure

Comments:

  1. Sam

    I’m gonna increase my salt intake. I drink a lot of water and think I’m peeing all the sodium out.

  2. Francisco

    Hi
    can I put your article on my facebook
    thanks

  3. sridevi

    nice post

  4. Maria Jasmine Freeman

    V important subject; thanks.
    Hypovolemia, one cause being too low sodium intake- triggers vasoconstriction, which on the long run causes structural changes at the renal vessels level, paving the way for-paradoxically- hypertension! Effect of too much salt intake, on the other hand, seems to promote high blood pressure, at least in a certain patient group. With this, the best option as to salt intake, is moderation; the key question remains, what salt intake is moderation?!?

  5. Dr. Ashraf Chaudhry

    For healthy and long life, we should limit salt as well as sugar in our diets. Sugar is more dangerous than salt and cause of inflammation in our body. Inflammation, we know cause of heart disease, diabetes and cancer. So say goodbye to soda/soft drinks and other sugary beverages.

  6. Dr Sameer Kauchali, Cape Town - Vitamin D- Hormone Foundation of South Africa

    I believe we have forgotten the role of potassium – it is the relationship between the sodium and potassium levels that determine the BP. If this ratio is skewed then problems arise. Potassium and sodium are cotransported accross the cell membranes of cells.

    So if one restricts salt, then it affects the potassium levels as well – this could explain the increased morbidity and moratality in those patients.

    • Geri L Weber RN,BSN

      the adulterated salt found in the USA is the worst culprit.It is stripped of ALL beneficial minerals. Add to that the high amount of sodium found in our processed foods and you have a recipe for disaster. Pink Himalayan salt is a HEALTHY (True Salt is another) alternative. In addition, if a moderate amount of of a healthy salt is used in cooking- the food tastes better making addition of more salt at the table unnecessary!!! Wake up folks!!As usual ” the studies” were skewed to support any number of the commercial endeavors that are found in our society!!!

    • Indu Saxena

      Dear Dr. Kauchali,

      I am grateful to you for pointing out the balance between SODIUM and POTASSIUM that the body’s CONTROL SYSTEM maintains, and that’s what determines cardiovascular health, including blood pressure.

      There is a true story I will share – of a senior person who was hospitalized and showed LOW SODIUM in the blood., who already ate salt sparingly, with NO PROCESSED foods in the diet The hospital discharged the patient a day later, saying the diet needs to be LOW in SODIUM due to there being a case of CHF , and reduced kidney function.
      The patient went OFF ANY ADDED salt COMPLETELY.
      One week later, the patient had to be taken to ER due to repeated throwing up.
      The DIAGNOSIS = VERY HIGH POTASSIUM !!

      That indicates clearly – that the SODIUM-POTASSIUM balance was disturbed sufficiently by STOPPING added salt to result in an emergency condition.

      Your thoughts ?

      -Indu

  7. Jan Purcell

    I believe every thing in moderation. One minute they some thing is bad for you, then later they say it’s good for you.

  8. Khatib

    Good hear from professionals, and see how knowledge is exchanged.
    Keep it up.

  9. Bill Morton

    There is no way that I will buy into the theory that increased salt consumption will promote better health. Even if you are a vegan or vegetarian, you are still getting plenty of salt in your diet if you refuse to use when cooking, and avoiding it in restaurant and take out foods.

  10. Bob

    Normally I read a lot of alternative health stuff and compare Harvard newsletter as the standard for conventional medical thinking and see what the difference is. This is a good article and believable on sodium intake than what I have read in alternative articles. Honesty and thoughtful thinking wins out in the long run and establishes a good reputation that readers can follow with some confidence.

    • shirley sink

      I am a senior. My blood pressure is always 120/65 give or take 5. My highest pressure ever was 140/82. I had heart stents 13 yrs ago. My blood wk shows I’m on the low end of sodium. I don’t watch my salt intake because I look & feel dehydrated.I drink lots of water. The nite before my last blood work I had a large bowl of salty pop corn. My blood pressure was 114/64. It puzzles me.

  11. Paulo Junior

    Muito bom!!

    Frases de Feliz Aniversário

  12. account user

    What bunch of dummies. 🙁
    One would think they would be embarrassed to create a poor study like that.
    We need more intelligent people like engineers in medical schools
    rather than the present crew who just memorize everything.

    I seem to know more about cardiovascular disease than my cardiologist.
    She keeps throwing 25 year-old dogma at me. Doesn’t she read current papers???

  13. Craig Blurton

    How do you respond to the studies described in this article published in Scientific American in 2011? I think the question is not a clear-cut as you would have us believe.

    It’s Time to End the War on Salt, Scientific American, July 8, 2011: Melinda Wenner Moyer.

  14. Jerry Amos

    We eat mostly whole foods with little processed foods. We don’t add any salt. My blood test shows comfortably mid-range sodiium. We do a little kelp for iodine. Mostly salt is used by Food, Inc. because it is a very cheap spice, who cares about harm.

  15. Sue O

    My husband and I do not add extra salt to our food. I do add the amount required in recipes. We are also trying to cut our intake of salty processed snacks and eat more fruits and vegetables. I think this is sensible.

  16. Chuck Bluestein

    There definitely is a flaw but it is not where it is guessed to be. It is right in front of you. I know about from salt levels from people who fast. They consume no salt but have salt levels in their urine that are insanely high. The flaw is that the more sodium that you consume, the less is in your urine.

    Salt is not a food and is terrible for health. Who would you guess to have more nicotine in their urine– the person who is chain smoker or the person that does not smoke at all, but just quit smoking.

  17. Robert Bramel

    Have the authors of this article read the material they reference!? Apparently not. Following the links in this article leads to the NEJM “Urinary Sodium and Potassium Excretion, Mortality, and Cardiovascular Events”. This article is sited as the evidence that elevated sodium is bad, and yet:

    “In this study in which sodium intake was estimated on the basis of measured urinary excretion, an estimated sodium intake between 3 g per day and 6 g per day was associated with a lower risk of death and cardiovascular events than was either a higher or lower estimated level of intake.”

    Three to six grams per day is best?! From the NEJM? who knew?

    This article argues that 3 grams or less is associated with worse outcomes; a position that is consistent with the “awful” Lancet study and quite inconsistent with the 2.3 or 1.5 grams that is supposedly ideal.

  18. Mark Jackman, PhD

    Nice, clear explanation of the methodological issues behind the headline results. Those headlines were a disservice to the many people who haven’t studied research methodology and end up feeling bewildered by the volatility of findings and recommendations. It was confusing enough to those of us who have studied these issues.

  19. norbert boruett

    This quiet confusing, nonetheless, more research needs to be done, in the absence of randomization, one has to take the findings with a pinch of salt.

  20. Mariam R

    Yikes, this is good advice… really tough to take heed of though considering sodium is in EVERYTHING. My cardiologist always encourages me to make the best decisions with my diet, as challenging as it can be sometimes.

  21. Gael C.

    My mother-in-law, a few years ago in her late 80s (she’s now 92), followed her doctor’s recommendation for a low-salt diet and got very sick when her blood sodium dropped too low. The nephrologist prescribed full-salt Campbell’s chicken noodle soup until she got better and advised her to stop restricting salt in her regular diet. So it can happen that someone can reduce their salt intake too much. Just saying.

  22. Richard H. Serlin

    So what do you think is too low a sodium level, given that a certain amount of salt is essential for cell function? And for children, crucially with developing bodies and brains, do they need more sodium? You certainly don’t want to be deficient in anything with this development, as important as it is.

    Maybe there are serious problems with this Lancet study, but there was a similar JAMA study before it, perhaps they do allude to problems from too little sodium for cell function? In any case, it would be well worth the money to do a new, extremely well devised, extensive study to really resolve these questions.

  23. DPBF

    Dr. Fisher, with all due respect, your statement, “A wealth of rigorous scientific studies supports a link between excess sodium intake and high blood pressure, heart attacks, and strokes” is categorically false. (Note that epidemiological data present a stark contradiction regarding the relationship between dietary sodium intake and incidence of hypertension in populations. In fact, the complete opposite is borne out by comprehensive examination of the science. To date, the wealth of science does not support the reduction of sodium in the diets of healthy persons. (NB: The assumption is that obesity is not to be considered a state of good health.) For example, an analysis of salt intake and hypertension published in fall, 2010, by Adam Bernstein, PhD, and Walter Willett, MD, PhD, of the Harvard School of Public Health showed sodium consumption in the American diet to be essentially unchanged over more than half a century…yet incidence of hypertension had risen dramatically in the same time period. If hypertension cases have gone up, but salt intake has stayed the same, it’s not the salt. Scientific data to date indicate that only for some 4-10% of persons at most—estimates vary according to studies—would restricting intake of sodium be at least somewhat helpful in controlling blood pressure. But for the 90+% who are perfectly healthy, it would not, and for some populations, such as the elderly, it can even be harmful. Ironically, about 4% of persons in the U.S. are currently living with cancer. As an MD, would you advocate treating every man, woman and child in the country with radiation and chemotherapy “just in case?” After all, cancer kills ten times as many persons as hypertension.

  24. Dr Samir

    Sir
    High blood pressure not caused only from inteacellular at physiological point of view
    From sodium as the main cause..
    You may get HBP from kidney or from vascular or from psychological factor..or from heart itself

    Advise to have balancing food for normal healthy
    Life
    Plus a check up periodically..
    And be practacing some good style in life
    Sport..and musical..
    Walking with good partner to talk with..
    Thanks

  25. Claudia

    What is the most reliable way for an average person to know what their sodium intake/measurement actually is? I was diagnosed with HYDROPS after having hearing loss and constant aural fullness-sometimes earaches. My ENT recommended a salt reduced diet, no caffeine and vitamins with heavy B-12. Blood pressure 120/70 HR 55. 68 year old female. not obese. Thanks for keeping us informed w/o charging for each report.

  26. Bill

    I love salt and at 70 my blood pressure is 116/74 which I’m happy with. Heart rate was 58 and 57. I’ve always been active but I would rather cut sugar which I don’t than salt.

  27. Margae

    Thank you for including the whole article. So nice not to have to buy a booklet to get beyond the headline to the “rest of the story.”

  28. james wightman

    What about people like me who eat almost no processed food, live in the desert, participate in endurance sport, and make sure that I drink plenty of water?

    My blood pressure is fine and i don’t take medication.

    Do you think that I should stop salting my food?

    • Bill

      James, good point. I only eat fresh foods, as many years ago someone said “if man made it don’t eat it.” I do eat meat not as much now as when I was younger but only eat fresh cuts

  29. James R

    My problem with all of this: I have high blood pressure and I have low sodium blood levels. I have removed the water pill from my bp regimen, and I have begun having a glass of v8 or a small dish of cottage cheese daily. I suspect I’d ruled out all salt, but for restaurant dishes, and perhaps it was too much. I’ll be interested to see what my bp and sodium levels are at next doc visit.