Take the 2-minute tour ×
Skeptics Stack Exchange is a question and answer site for scientific skepticism. It's 100% free, no registration required.

Salt is sometimes known as "white death" due to the belief that an excess intake of salt can cause substantial damage to health.

What evidence exists to support or contradict the idea that excess salt intake can cause substantial health damage? Is it better to avoid salt altogether?

share|improve this question
2  
and no, just because some dose is lethal doesn't mean you should not consume/ingest something at all. Oxygen is lethal, so is water. Yet without it you'd die quickly. The human body needs cyanide, yet more than a few micrograms will kill you. And it's the same with salt as well. That said, an average human being gets enough salt for his daily dietary requirements through his normal food intake (especially processed foods, breads, etc.) and doesn't need to add salt to his diet explicitly by salting his food extra. –  jwenting Mar 8 '11 at 8:04
    
jwenting: "the human body needs cyanide" - any source on that? I'd be very surprised if it is the case. –  johanvdw Sep 26 '11 at 11:03
1  
Scientific American has an interesting article - scientificamerican.com/… –  DanBeale Sep 26 '11 at 15:37
    
I don't know if this shows the NEED for it, but it does indicate it can be USED to make vitamin B-12. (see section called "How does cyanide act in the body?") –  fred Sep 26 '11 at 18:12

4 Answers 4

up vote 28 down vote accepted

Toxicity of a substance must be investigated in different ways:

  1. Acute toxicity

    This corresponds to taking a large dose all at once. In the case of sodium chloride, toxic effects are encountered at 500-1000 mg/kg body weight. The effects include vomiting, ulceration of the gastrointestinal tract, muscle weakness and renal damage, leading to dehydration, metabolic acidosis and severe peripheral and central neural effects.
    The estimated fatal dose of sodium chloride is approximately 750 to 3000 mg/kg.
    Also see (1, 2) for many more sources.

  2. Chronic toxicity

    This includes non-carcinogenic effects on health. There seems to be a link between salt intake and some hypertrophy of the heart - which is a risk factor for heart disease. The generally known medical advice to use less salt is actually due to a different factor: reducing salt reduces blood pressure in hypertonic subjects. In other words, if you have high pressure, then reducing salt is beneficial. The effect of reducing salt in individuals with normal pressure instead is disputed.

    Reduction of dietary sodium is generally recommended as a nonpharmacological treatment for patients with essential hypertension. In normotensive adults a significant reduction in sodium intake is needed to achieve a modest reduction in blood pressure.

  3. Carcinogenic effects

    Salt has no known carcinogenic effects and no carcinogenic effects are expected to be found (1, 2).

share|improve this answer
3  
Further data regarding salt toxicity –  Casebash Mar 8 '11 at 12:04
    
there might also be potentially non-toxic yet health-detrimental effects from Sodium/Potassium imbalance (it's been a long while since I read on the topic so don't remember any details) –  DVK Jun 21 '11 at 17:22
    
The conclusion of this 2011 study was that people with the lowest levels of sodium intake at the start of the study had a 56 percent higher risk of dying from cardiovascular disease than people with the highest levels. Moreover, among those participants who had normal blood pressure at the start of the study, urinary sodium appeared to have no effect on the development of high blood pressure over six and a half years. –  elbatrofmoc Sep 19 '12 at 9:10

Signs don't look so good. See this article http://www.cspinet.org/nah/articles/salt.html, which refers to a number of recent (and not so recent) studies. (There are references to the actual studies in the PDF version; oddly in the html article the superscript numbers are there but the notes are missing.) Some highlights:

  • A 2009 meta-analysis of 13 studies found that cutting salt reduces blood pressure and also lowers risk of heart attacks and strokes
  • long-term exposure to excess sodium means eventual high blood pressure for 90% of Americans
  • even moderate blood pressure is associated with increased risk
  • there's some suggestion that elevated blood pressure may be associated with dementia
  • there's suggestion that salt is harmful to the cardiovascular system directly, regardless of pressure

Note that many of the studies are newer than the 2003 paper referenced in Sklivvz's answer.

share|improve this answer
    
Direct link to the 2009 meta-analysis: bmj.com/content/339/bmj.b4567.full –  mattdm Mar 9 '11 at 13:37
5  
I prefer to have at least moderate blood pressure. –  Peter G. Apr 21 '11 at 14:28

In addition to the other answers:

Does this mean that it is best not to use any salt at all?

Certainly not. Salt is necessary. If you don't eat enough salt you may end up with hyponatremia.

From wikipedia:

Hyponatremia is the most common electrolyte disorder. Its frequency is higher in females, the elderly, and in patients who are hospitalized. The incidence of hyponatremia depends largely on the patient population. A hospital incidence of 15–20% is common, while only 3–5% of patients who are hospitalized have a serum sodium level of less than 130 mEq/L. Hyponatremia has been reported in up to 30% of elderly patients in nursing homes and is also present in approximately 30% of depressed patients on selective serotonin reuptake inhibitors.[2]

Apart from them it is a condition which is quite common in people who are running a marathon and loose a lot of salt through sweating, while drinking too much water See eg: http://www.nejm.org/doi/full/10.1056/nejmoa043901

This is also true for less intensive sports:

Sodium depletion is a recurrent theme in heat cramping, and is reported to be one of the factors contributing to cause, treatment, and prevention of exercise-associated muscle cramps . Stone, M.B., J.E. Edwards, C.L. Stemmans, C.D. Ingersoll, R.M. Palmieri, and B.A. Krause. Certified athletic trainersʼ perceptions of exercise-associated muscle cramps. J. Sports Rehab. 12:333-342, 2003. cited in http://www.csun.edu/~lisagor/2009%20Fall/608-09Fall/608-1.Sweat%20and%20Sodium%20Losses%20in%20NCAA%20Football%20Players.pdf

In that paper you will also notice that some people lose a lot of salt through sweating, and for those people salt intake has to be higher.

Finally since this site is about skepticism: some groups are clearly vulnerable to hyponatremia. For those people it is perhaps a bad advice to limit salt intake. The major reason why salt is seen as 'bad' is the fact that it causes high blood pressure. But it only influences high blood pressure in a relatively small group of people. See eg:

Dietary sodium restriction for older hypertensive individuals might be considered, but the evidence in the normotensive population does not support current recommendations for universal dietary sodium restriction. "

http://jama.ama-assn.org/cgi/content/abstract/275/20/1590

One segment of the public health community—funded by the the Na- tional Heart Lung and Blood Institute and endorsed by many journals in the field—has decided that salt is a public health menace. Therefore, salt consumption must be drastically curtailed. The force with which this conclusion is presented to the public is not in any reasonable balance with the strength of the evidence.

http://www.stat.berkeley.edu/~census/573.pdf

share|improve this answer
    
whoever downvoted: please explain why. There is a reference, and I think this answer (although short) is a useful addition to the other answers because it focuses on a part of the question that was not covered in the other answers. –  johanvdw Sep 26 '11 at 12:41
    
Since salt is actually contained in almost all that we eat, not adding any salt would not necessarily lead to hyponatraemia... your reference supports that salt is necessary, not that not using salt at all is a bad thing (which is your main claim). –  Sklivvz Sep 26 '11 at 13:08
    
Sklivvz: the question is literaly: "Does this mean that it is best not to use any salt at all?". That would exclude things that you eat that contain salt. I've expanded my answer, because I do think we should be more skeptical on the salt recommendations. I know for sure that I have to take care that I eat enough salt. But I'm not eating a lot of processed food that contains sugar and saturated fats (that lead to high blood pressure), and I do exercise a lot (which leads to a lower blood pressure). –  johanvdw Sep 26 '11 at 14:07
    
When I exercise, especially long distance running, I need to east a small handful of salt afterwards otherwise I get painful cramps, as I get very little salt in my diet- avoiding processed foods reduces your salt intake dramatically –  Rory Alsop Sep 26 '11 at 16:59

It is possible to consume a lethal dose of salt, especially for small children. There has been at least one case where an adult died of a salt overdose. In this case 45-60 grams were consumed, but the lethal dose is estimated to be lower. The lethal dose is also far smaller for children.

share|improve this answer
2  
It is also possible to die of a water or oxygen overdose :) –  the JinX Mar 10 '11 at 14:44

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.