6 ms·

So, I always cringe a little when I read medical conclusions in the mainstream media. And I'll be upfront. I'm probably biased on the side of medicine on this

by arn 14y ago

So, I always cringe a little when I read medical conclusions in the mainstream media. And I'll be upfront. I'm probably biased on the side of medicine on this one. I'm a former nephrologist. The one study this person mentions by name (and dismisses) is the DASH-Sodium Study. http://en.wikipedia.org/wiki/DASH_diet#Study_Results http://en.wikipedia.org/wiki/DASH_diet#Study_Results "Like the previous study, it was based on a large sample (412 participants) and was a multi-center, randomized, outpatient feeding study where the subjects were given all their food." "The DASH-Sodium study found that reductions in sodium intake produced significantly lower systolic and diastolic blood pressures in both the control and DASH diets. Study results indicate that the quantity of dietary sodium in the control diet was twice as powerful in its effect on blood pressure as it was in the DASH diet." So, positive conclusions (lower salt -> lower blood pressure) in a seemingly well designed study. People were randomized, it was prospective, and people given all their food. So, change one thing and see what happens. The author here seems to cite other studies to make the opposing case (low salt = bad), but doesn't give exact references. I did a quick google search and found this one: http://www.nytimes.com/2011/05/04/health/research/04salt.html http://www.nytimes.com/2011/05/04/health/research/04salt.htm... But you can already tell it's an inferior study. "It involved only those without high blood pressure at the start, was observational, considered at best suggestive and not conclusive." So, let's try to compare apples to apples. He points out that the DASH study didn't conclude anything about death or cardiovascular disease. Yes, that's true. So sure, there's a chance that despite blood pressure reductions a low salt diet could cause problems. But it's not the obvious conclusion. Anyone have any solid studies on this?

streptomycin 14y ago
> I always cringe a little when I read medical conclusions in the mainstream media. I usually do too, especially articles about nutrition which are notoriously unreliable due to the near complete lack of randomized, controlled, prospective studies and the abundance of observational studies, but this one doesn't seem too bad. In fact, the same author published a similar article in Science last millennium http://www.stat.berkeley.edu/users/rice/Stat2/salt.html http://www.stat.berkeley.edu/users/rice/Stat2/salt.html so I don't think you can blame the mainstream media too much here if they're just printing an article similar to what would satisfy Science's editorial standards.
cperciva 14y ago
there's a chance that despite blood pressure reductions a low salt diet could cause problems For that matter, there's a chance that because of blood pressure reductions, a low salt diet could cause problems -- if the kidneys respond to low blood pressure by secreting renin, and renin causes more cardiovascular damage than high blood pressure.
splat 14y ago
Taubes has written a bit about salt before. Unfortunately, the only thing he's written that I can find that goes into more detail is this Science news focus article: http://www.sciencemag.org/content/281/5379/898.full http://www.sciencemag.org/content/281/5379/898.full It talks about the DASH study and some others in a little more detail, but unfortunately it's 14 years old now, so I don't know what research has been done since.
ellyagg 14y ago
Scientific American has also had a couple articles about this recently. Here's one: http://www.scientificamerican.com/article.cfm?id=its-time-to-end-the-war-on-salt http://www.scientificamerican.com/article.cfm?id=its-time-to...
crazygringo 14y ago
> He points out that the DASH study didn't conclude anything about death or cardiovascular disease. Yes, that's true. So sure, there's a chance that despite blood pressure reductions a low salt diet could cause problems. But it's not the obvious conclusion. That's the whole point, you say it yourself. The idea that "salt is bad" has just as shaky underpinnings as "lower blood pressure is good". The only thing we care about is death or disease, not lowering blood pressure. So even if less salt = lower blood pressure, that doesn't tell us if this is good, or harmful. The obvious conclusion is that there is no conclusion.
- arn 14y ago
  > The idea that "salt is bad" has just as shaky underpinnings as "lower blood pressure is good". Wait, "lower blood pressure is good" has shaky underpinnings? Is there a debate on that? I don't think there's a debate that high blood pressure results in worse (death/disease) outcomes.
  - nessus42 14y ago
    Well, my mother had a stroke due to low blood pressure, so it's certainly not the case that lower is always better.
  - j_baker 14y ago
    Indeed. But is lower blood pressure good in a person who doesn't have high blood pressure? This is a serious question too. :-)
    - arn 14y ago
      If you have normal* blood pressure, you don't have to lower it anymore. In fact, there's a J shaped curve for Blood pressure. Too high or too low, you're at increased risk of dying. http://en.wikipedia.org/wiki/J_curve#Medicine http://en.wikipedia.org/wiki/J_curve#Medicine * definition of normal may change over time.
      - 14y ago
Symmetry 14y ago
I believe the contention is that studies like DASH show that changes in sodium consumption, rather than levels of sodium consumption, can effect blood pressure. That is, if you go onto a low sodium diet your blood pressure will fall, but then rise again to its previous level as your body adjusts.
joe_the_user 14y ago
Uh, He points out that the study followed people for 30 days. And made recommendations for life-long behavior. And wasn't looking at final results but markers (blood pressure). And was the main argument against salt consumption when we do have some data on people's life-long behaviors and their result. And this wasn't "medicine" that spoke but a particular institution making recommendations. Edit: removed possibly inflammatory point
- arn 14y ago
  Re 30 days. I get it. If you want to argue that the general mass population doesn't benefit from salt restriction, I wouldn't argue very strongly against it. But he seems to suggest salt restriction harmful to the masses? I want more data on that than what's offered.
  - rsheridan6 14y ago
    This study, which received a lot of attention about a year ago, is probably what he's referring to: http://jama.jamanetwork.com/article.aspx?articleid=899663 http://jama.jamanetwork.com/article.aspx?articleid=899663 "The associations between systolic pressure and sodium excretion did not translate into less morbidity or improved survival. On the contrary, low sodium excretion predicted higher cardiovascular mortality."
alan-crowe 14y ago
I think that the Cochrane reviews mentioned are these two http://summaries.cochrane.org/CD009217/advice-to-reduce-the-amount-of-salt-eaten-reduces-blood-pressure-but-there-is-insufficient-evidence-to-confirm-the-predicted-reductions-in-people-dying-prematurely-or-suffering-cardiovascular-disease http://summaries.cochrane.org/CD009217/advice-to-reduce-the-... http://summaries.cochrane.org/CD002128/dietary-advice-for-reducing-cardiovascular-risk http://summaries.cochrane.org/CD002128/dietary-advice-for-re...
blantonl 14y ago
nephrologist = branch of internal medicine and pediatrics dealing with the study of the function and diseases of the kidney.[1] [1] Wikipedia: http://en.wikipedia.org/wiki/Nephrology http://en.wikipedia.org/wiki/Nephrology
niels_olson 14y ago
arn, thanks for leading this one! Let me chime in that salt no doubt drives caloric intake. One need look no further than chefs and fast food to figure that out. So, in my mind, salt is a double whammy: BP and a secondary cause of weight gain, cholesterol, and everything else that comes with weight gain.
rsheridan6 14y ago
If you look at the numbers in the Wiki link you provided, the reduction in BP in DASH dieters was small in non-hypertensives and not exactly huge in hypertensives. "Respectively, the DASH or “combination” diet lowered blood pressures by an average of 5.5 and 3.0 mm Hg for systolic and diastolic, compared with the control diet. The minority portion of the study sample and the hypertensive portion both showed the largest reductions in blood pressure from the combination diet against the control diet. The hypertensive subjects experienced a drop of 11.4 mm Hg in their systolic and 5.5 mm Hg in their diastolic phases." I question whether the 5.5/3 mmHg is really worth eating bland low sodium food. Statistical significance does not necessarily imply clinical significance, and you're asking people to give up something pretty big. Willpower is a limited resource. We should have good reasons to ask people to use it up. Here's an abstract of a metaanalysis which reaches roughly the same conclusion: http://www.nature.com/ajh/journal/v24/n8/full/ajh2011115a.html http://www.nature.com/ajh/journal/v24/n8/full/ajh2011115a.ht...
- einhverfr 14y ago
  I'd agree. I have had times in my life where I have had to increase my salt consumption to avoid problems. These include everything from altitude sickness to dehydration caused by eating a diet too high in fruit. However, at the same time I don't think that things are as clear-cut as in the article. One of the serious issues we find in current dietary trends is that we eat more prepared foods which tend to be high in salt, hydrogenated oils, and sugars. So I personally side both with the idea that we have gone overboard in trying to reduce salt and also the idea that the modern American diet tends towards too much salt. I would also make the somewhat controversial argument that I think that anything we replace salt with will be even worse. The solution is to eat more fresh foods and fewer junk foods and prepared foods, not try to engineer some sort of low sodium equivalents.

by arn 14y ago

streptomycin 14y ago

> I always cringe a little when I read medical conclusions in the mainstream media. I usually do too, especially articles about nutrition which are notoriously unreliable due to the near complete lack of randomized, controlled, prospective studies and the abundance of observational studies, but this one doesn't seem too bad. In fact, the same author published a similar article in Science last millennium http://www.stat.berkeley.edu/users/rice/Stat2/salt.html http://www.stat.berkeley.edu/users/rice/Stat2/salt.html so I don't think you can blame the mainstream media too much here if they're just printing an article similar to what would satisfy Science's editorial standards.

cperciva 14y ago

there's a chance that despite blood pressure reductions a low salt diet could cause problems For that matter, there's a chance that because of blood pressure reductions, a low salt diet could cause problems -- if the kidneys respond to low blood pressure by secreting renin, and renin causes more cardiovascular damage than high blood pressure.

splat 14y ago

Taubes has written a bit about salt before. Unfortunately, the only thing he's written that I can find that goes into more detail is this Science news focus article: http://www.sciencemag.org/content/281/5379/898.full http://www.sciencemag.org/content/281/5379/898.full It talks about the DASH study and some others in a little more detail, but unfortunately it's 14 years old now, so I don't know what research has been done since.

ellyagg 14y ago

Scientific American has also had a couple articles about this recently. Here's one: http://www.scientificamerican.com/article.cfm?id=its-time-to-end-the-war-on-salt http://www.scientificamerican.com/article.cfm?id=its-time-to...

crazygringo 14y ago

> He points out that the DASH study didn't conclude anything about death or cardiovascular disease. Yes, that's true. So sure, there's a chance that despite blood pressure reductions a low salt diet could cause problems. But it's not the obvious conclusion. That's the whole point, you say it yourself. The idea that "salt is bad" has just as shaky underpinnings as "lower blood pressure is good". The only thing we care about is death or disease, not lowering blood pressure. So even if less salt = lower blood pressure, that doesn't tell us if this is good, or harmful. The obvious conclusion is that there is no conclusion.

arn 14y ago
> The idea that "salt is bad" has just as shaky underpinnings as "lower blood pressure is good". Wait, "lower blood pressure is good" has shaky underpinnings? Is there a debate on that? I don't think there's a debate that high blood pressure results in worse (death/disease) outcomes.
- nessus42 14y ago
  Well, my mother had a stroke due to low blood pressure, so it's certainly not the case that lower is always better.
- j_baker 14y ago
  Indeed. But is lower blood pressure good in a person who doesn't have high blood pressure? This is a serious question too. :-)
  - arn 14y ago
    If you have normal* blood pressure, you don't have to lower it anymore. In fact, there's a J shaped curve for Blood pressure. Too high or too low, you're at increased risk of dying. http://en.wikipedia.org/wiki/J_curve#Medicine http://en.wikipedia.org/wiki/J_curve#Medicine * definition of normal may change over time.
    - 14y ago

Symmetry 14y ago

I believe the contention is that studies like DASH show that changes in sodium consumption, rather than levels of sodium consumption, can effect blood pressure. That is, if you go onto a low sodium diet your blood pressure will fall, but then rise again to its previous level as your body adjusts.

joe_the_user 14y ago

Uh, He points out that the study followed people for 30 days. And made recommendations for life-long behavior. And wasn't looking at final results but markers (blood pressure). And was the main argument against salt consumption when we do have some data on people's life-long behaviors and their result. And this wasn't "medicine" that spoke but a particular institution making recommendations. Edit: removed possibly inflammatory point

arn 14y ago
Re 30 days. I get it. If you want to argue that the general mass population doesn't benefit from salt restriction, I wouldn't argue very strongly against it. But he seems to suggest salt restriction harmful to the masses? I want more data on that than what's offered.
- rsheridan6 14y ago
  This study, which received a lot of attention about a year ago, is probably what he's referring to: http://jama.jamanetwork.com/article.aspx?articleid=899663 http://jama.jamanetwork.com/article.aspx?articleid=899663 "The associations between systolic pressure and sodium excretion did not translate into less morbidity or improved survival. On the contrary, low sodium excretion predicted higher cardiovascular mortality."

alan-crowe 14y ago

I think that the Cochrane reviews mentioned are these two http://summaries.cochrane.org/CD009217/advice-to-reduce-the-amount-of-salt-eaten-reduces-blood-pressure-but-there-is-insufficient-evidence-to-confirm-the-predicted-reductions-in-people-dying-prematurely-or-suffering-cardiovascular-disease http://summaries.cochrane.org/CD009217/advice-to-reduce-the-... http://summaries.cochrane.org/CD002128/dietary-advice-for-reducing-cardiovascular-risk http://summaries.cochrane.org/CD002128/dietary-advice-for-re...

blantonl 14y ago

nephrologist = branch of internal medicine and pediatrics dealing with the study of the function and diseases of the kidney.[1] [1] Wikipedia: http://en.wikipedia.org/wiki/Nephrology http://en.wikipedia.org/wiki/Nephrology

niels_olson 14y ago

arn, thanks for leading this one! Let me chime in that salt no doubt drives caloric intake. One need look no further than chefs and fast food to figure that out. So, in my mind, salt is a double whammy: BP and a secondary cause of weight gain, cholesterol, and everything else that comes with weight gain.

rsheridan6 14y ago

If you look at the numbers in the Wiki link you provided, the reduction in BP in DASH dieters was small in non-hypertensives and not exactly huge in hypertensives. "Respectively, the DASH or “combination” diet lowered blood pressures by an average of 5.5 and 3.0 mm Hg for systolic and diastolic, compared with the control diet. The minority portion of the study sample and the hypertensive portion both showed the largest reductions in blood pressure from the combination diet against the control diet. The hypertensive subjects experienced a drop of 11.4 mm Hg in their systolic and 5.5 mm Hg in their diastolic phases." I question whether the 5.5/3 mmHg is really worth eating bland low sodium food. Statistical significance does not necessarily imply clinical significance, and you're asking people to give up something pretty big. Willpower is a limited resource. We should have good reasons to ask people to use it up. Here's an abstract of a metaanalysis which reaches roughly the same conclusion: http://www.nature.com/ajh/journal/v24/n8/full/ajh2011115a.html http://www.nature.com/ajh/journal/v24/n8/full/ajh2011115a.ht...

einhverfr 14y ago
I'd agree. I have had times in my life where I have had to increase my salt consumption to avoid problems. These include everything from altitude sickness to dehydration caused by eating a diet too high in fruit. However, at the same time I don't think that things are as clear-cut as in the article. One of the serious issues we find in current dietary trends is that we eat more prepared foods which tend to be high in salt, hydrogenated oils, and sugars. So I personally side both with the idea that we have gone overboard in trying to reduce salt and also the idea that the modern American diet tends towards too much salt. I would also make the somewhat controversial argument that I think that anything we replace salt with will be even worse. The solution is to eat more fresh foods and fewer junk foods and prepared foods, not try to engineer some sort of low sodium equivalents.