Is It Time to End the “War on Salt”?

Photo: DaGoaty

The assault on dietary salt has been growing, and salt sales have been trending slightly downward. Is this a good fight?

According to Scientific American, perhaps not:

This week a meta-analysis of seven studies involving a total of 6,250 subjects in the American Journal of Hypertension found no strong evidence that cutting salt intake reduces the risk for heart attacks, strokes or death in people with normal or high blood pressure. In May European researchers publishing in the Journal of the American Medical Association reported that the less sodium that study subjects excreted in their urine—an excellent measure of prior consumption—the greater their risk was of dying from heart disease. These findings call into question the common wisdom that excess salt is bad for you, but the evidence linking salt to heart disease has always been tenuous.

(HT: Eric Jones)

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  1. Graham says:

    The Nature News take on the meta-analysis is much more balanced:

    Essentially, the authors concluded that reducing salt does indeed lower blood pressure, which would suggest that lowering salt is good for heart disease. However, they were unable to show a relationship between reducing salt intake and lowering heart disease. But this doesn’t mean there is no relationship. It just means more research would need to be done to demonstrate it.

    Science with human subjects is hard.

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    • Neil (SM) says:

      It seems too much research is done with the premise of “lets keep researching until we can prove x,” rather than “lets determine if x or y is true.”

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    • anomdebus says:

      If this were a merely academic discussion, then you are completely on point. However, as it is, there are serious pushes to regulate salt content with no proven relationship between intake and health effects. Since there is also some evidence that too low salt intake can impact health, forcing a low salt diet isn’t necessarily a matter where it would at worse do no harm.

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      • Graham says:

        On that point, I agree. I’ve been fascinated watching how the press covers this story, as it seems journalists don’t know how to report on inconclusive results. But inconclusive results do mean that it would be crazy to start regulating salt as has been proposed, just as it would be crazy for someone with hypertension to start eating an all-bacon diet.

        But since my last comment, I’ve actually gone back to read the paper. Assuming the analysis was correct — I am not a biologist or an MD, so I’m not qualified to judge — then even the relationship between salt and blood pressure is tenuous.

        Given the attention this issue has gotten, it would seem funding should be available for a new larger study to start answering these questions.

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  2. Tom Megginson says:

    I blogged about this 2 years ago:

    My issue with the “war on salt” is that it takes a real public health issue and destroys all credibility for the cause by overstating the dangers. An average, healthy person is not in deadly danger for occasional pizza, pickles, or chips. The real issue is the mass quantities of hidden sodium in processed foods that people at risk of high blood pressure, hypertension or heart disease consume without thinking.

    As a social marketing cause, the anti-salt people make the same mistake as the “War on Drugs” when it implies that smoking a joint will destroy your life. It goes against common sense and experience, and it only hurts the argument when it’s made for the dangers of harder drugs.

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  3. oliver street says:

    Hidden due to low comment rating. Click here to see.

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    • TonyDanzaPervo says:

      This comment makes little sense. There is already a multiplicitive effect between asbestos exposure and cigarette smoking. Smoking, combined with prolonged asbestos exposure, can increase the chance of lung cancer by up to 70 times. Chemicals in tobacco smoke can paralyze cilia movement used to extract particulate from the lung and airways, and the lungs are forced to defend against asbestos fibres, which cannot be broken down by the body, but against tar and particulate from smoking as well.

      As for salt, I believe earlier studies maybe looked past the fact that the obesity rate and number of people with heart disease from a sedentary lifestyle and comsumption of fast food and processed pre-packaged meals which have been a norm in North American life in recent history maybe have more to do with heart disease than salt intake as a single culprit. Salt is a scapegoat for a host of other problems that contribute to heart disease through the lifestyle (or lack there of) in North American households.

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    • Neil (SM) says:

      Cigarettes are the least common denominator in second-hand smoke. The threat of has been greatly overstated to the point of even prohibiting it in some outside areas where exhaust and other fumes are the elephant and cigarette fumes are the mouse of danger to others.

      First-hand smoke, on the other hand, is clearly more damaging to the smoker than all of the above.

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  4. LNS says:

    I agree this research brings into question the paradigm of attacking a public health problem like high blood pressure with a simplistic, overarching recommendation that will by definition be too broad to apply to many patients. Especially in rising health challenges like obesity, diabetes, high blood pressure, etc, the path from correlation to causation is much murkier than the more easily recognized health hazards of tobacco, on which many public health campaigns have been modelled. However, in the medical community it has been understood that some patients are salt-responders, and others are not. Factors of genetics and other demographic traits can help winnow down this population, as can a simple blood test seeing how a patients BP respond to salt intake. Thus, before we end a war- we might be better off starting a counterinsurgency targetted to those patients most likely to benefit from the decreased salt intervention. This is the downside of meta analyses- sometimes the proper subgroups that would benefit from a dietary modification are lost in the data.

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  5. Jonathan Bagley says:

    There are now efforts to portray salt as an addictive drug. See today’s UK Daily Mail.

    Well, why not? Pseudo science worked with passive smoking and, in the UK, the same people have moved on to alcohol and so called “junk food”. Anti this, anti that, anti the idea that somewhere, somebody is enjoying life without fresh air and exercise. All cheeks of the same anti arse.

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  6. Clifton Griffin says:

    I for one am glad everyone has avoided the “grain of salt” pun (except for possibly me, just now).

    If history teaches us anything, it’s that there is rarely a final word on any nutrition issue. Hence the endless ping pong of eggs are bad for you, eggs are good for you, eggs are bad for you, eggs are good for you, ad infinitum.

    As with many things, it seems the safest course is usually “everything in moderation”.

    This years poison may be next year’s fountain of youth. If anything, it’s a pretty darn good reason to not go changing laws all willy nilly. (I’m looking at you NYC)

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  7. Tadpoles says:

    It’s never made sense to me since sodium is so easily excreted in the urine that any increase in salt intake just leads to an almost immediate increase in salt in the urine, so any rise in blood pressure would be very transient.

    The only thing i’ve ever been able to find that seems like a link between salt and the CVD stuff is that possibly some people, after eating salt, have a genetic component that decreases the release of normally blood pressure lowering chemicals.

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  8. James says:

    Oddly enough, a new study* reported in the last few days finds that there is a connection. For myself, I just think food tastes better when I can taste something besides the salt.

    “Sodium and Potassium Intake and Mortality Among US Adults: Prospective Data From…”, Yang et al., Arch Intern Med.2011; 171: 1183-1191. Unfortunately it’s behind a paywall.

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    • RC says:

      That study establishes a link between high sodium/low potassium and heart disease compared to low sodium/high potassium then goes to mention that processed diets provide combination 1 and low processed diets provide combination 2. It does not provide a comparison to a low processed combo 1 or a high processed combo 2, so we do not know if the link is to processed foods and low fruits/vegetables or to the sodium.

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  9. frankenduf says:

    it is a simplification that is indirectly correct- the key is potassium to sodium ratio- the higher ratio of intake, the greater the cardioprotective effect- so it is more effective to eat high potassium diet- also, some are sodium sensitive (eg diabetics) and for them it is directly safer to decrease salt intake

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  10. JR says:

    Remember a few years ago there was a movement to have people eat a pH balanced diet? The purported benefit was more pH balanced blood. But pH is very tightly regulated in the blood and there are several mechanisms to make sure it happens. Blood salinity is the same thing, your body tightly regulates it in the blood and disposes of any excess.
    I’ve always seen the “salt is bad for you” rumor as another too-soon announced study that will lead to more distrust of nutrition science.

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    • Ted Pavlic says:

      Regulation has its limits. For example, if you had no salt intake and had to upregulate to maintain the proper salinity, your body would be stuck. The best it could do is expel excess water until your body was desiccated as well.

      Similarly with pH, your blood pH may be regulated, but this regulatory mechanism doesn’t come for free. A poor protein–carbohydrate balance in the diet can lead to kidney stones. After an incident with struvite crystals in his bladder, my dog was put on a prescription dog food for the rest of his life to reduce the regulation burden on his body, which has a genetic disposition for high pH. Consequently, we’ve also been told to increase the protein-to-carbohydrate ratio of any other food he gets by putting a high emphasis on proteins (which tend to make the blood more acidic).

      Regulation is not free. Imagine any servomechanism in your car; eventually the open-loop servo mechanism will saturate and no amount of feedback you provide will restore the system to its balance until you return the controller to its NORMAL operating region.

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  11. Nosybear says:

    I have to ask how you missed the headline “…Assault on Salt.”

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  12. Priscilla says:

    Apparently the study measured the amount of sodium excreted in urine, and correlated low output with heart disease,etc. This seems to suggest that dietary intake was not what was studied. So, perhaps it is the retention of salt that is the problem, or at least the correlation. Further study could determine why some people retain salt and others, not so much. When I was pregnant and my bood pressure was rising, I was put on a no salt diet (but in those days, mandatory labeling had not come into play so it was years later that I found I was actually eating a lot of sodium!) and my doctor managed to keep things somewhat in check by having me drink large quantities of water! Did the tests ask suibjects how much water they drank? My guess is that people hoo drink a lot of water get rid of a lot of sodium.

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  13. Anusheh says:

    Perhaps… I’m eating less because my food tastes worse

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  14. Sprocket says:

    In one of these studies as I saw it reported the authors explained the fact that lowering salt intake had no effect on stroke/death rates by:

    1) Less salt = lower blood pressure.
    2) Lower Blood pressure = fewer strokes/deaths
    3) Study did not show this to be true.
    4) Therefore we did not lower blood pressure enough, because everyone “knows” these results cannot be right.

    It seems to me there are actually a different set of truths here:

    1) Only in a few people (c25%?) does reduced salt reduce blood pressure.
    2) High Blood pressure is not a factor in death/stroke/heart disease until it is very very high (>200).

    I think you guys at Freakonomics should look at a whole bunch of these medical “truths” and dig deeper into the stats to see how many of them are wrong. Lowering cholesterol would be a good start, along with low fat diets. (If you have already done so forgive me!).

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    • Ted pavlic says:

      To understand salt’s impact on blood pressure, you have to recall what you learned about osmosis in primary and secondary school.

      In particular, the greater the salinity of the blood, the increased flow of water into the blood vessels across semipermeable membranes. This flow (call it osmosis, if you must, but it’s just diffusion of water) continues “until” the salinity is balanced on both sides. I say “until” in quotes because it actually goes on continuously, but the in-flow and out-flow balance at that point and so the net movement of water is zero. At that new point, there will have been more water moved into the blood vessels. That increase in water volume causes either an increase in blood pressure and/or an increase in vessel diameter. Either way, it’s an additional stress.

      You can imagine that these osmotic pressure differentials could cause lots of other problems throughout the body as well. Heck, consider crenation:

      So I hardly think it’s a fantasy to associate blood pressure with salinity. The question is how the body deals with the hypertonic blood. That’s one of the functions of urine. Keep in mind that in the summers, salt content in urine is especially high because humans sweat, and that sweating (which in general is tough on the heart muscle) drives out more water than salt and increases the salinity of the blood (if sweat were pure water, the problem would be much worse).

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      • miriam says:

        It is not clear why salt increases blood pressure. It does not seem to be a problem for every person, but if you reduce salt intake in a population you will see an effect from the people it does work in.
        For example, it is not clear why diuretics reduce blood pressure in the long term (hint: it is not about dehydration).
        I think the interesting work would be WHY a reduction in salt reduces blood pressure (especially in the long term, where you would expect it not to be a problem of fluid balance) and WHICH individuals it is effective in. A freakogenomics, if you will.
        I fear that line of research will not be popular…

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  15. Ted Pavlic says:

    So, from this little blurb, it appears like you’re saying the body’s ability to osmoregulate is hampered by the lack of salt availability? That is, as urine is the natural mechanism for osmoregulation in mammals (with perhaps sweat playing a role in less hairy mammals like humans), the suggestion seems to be that urine should do a good job balancing salinity (and thus blood pressure), but it can only UPregulate to the appropriate salinity (preventing low blood pressure) if salt is available.

    So it may suggest that having a little extra salt isn’t a bad thing (surely the body’s ability to osmoregulate with urine is limited on the other end though — there must be some limit to salt intake that wrecks things).

    Other studies (e.g., Simpson, Sword, Lorch, and Couzin (2006) in PNAS) suggest invertebrates do a good job balancing salt intake on their own if provided rich enough sources. It seems like that work could be incorporated here too. Right?

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  16. Gary says:

    You need salt to survive. The average person has to have 1/2 Lb. in their bodies at all times. No salt in your body 100% fatal.

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  17. Joshua Northey says:

    Unless you are very unhealthy you can have as much salt as you want as long as you drink enough water to flush it. Drink a gallon or 2 of water a day.

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  18. Nicole says:

    Thought you might be interested in a non-press filtered interpretation of the underlying work by someone who actually reads (and then interprets for the rest of “us”) medical research papers:

    Looks to me like dietary sodium is still a problem.

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  19. Brett Keller says:

    You should post a follow-up on this topic now that there’s a new Lancet paper picking apart the methodology and showing the authors were wrong to begin with:

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