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Health effects of salt

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SEM image of a grain of table salt

Chloride and sodium ions, the two major components of salt, are needed by all known living creatures in small quantities. Salt is involved in regulating the water content (fluid balance) of the body. The sodium ion itself is used for electrical signaling in the nervous system.[1]

Salt consumption has increased during modern times and scientists have become aware of the health risks associated with high salt intake, including high blood pressure in sensitive individuals. Therefore, some health authorities have recommended limitations of dietary sodium, although others state the risk is minimal for typical western diets.[2][3][4][5][6] The United States Department of Health and Human Services recommends that individuals consume no more than 1500–2300 mg of sodium (3750–5750 mg of salt) per day depending on age.[7]

Salt is sometimes used as a health aid, such as a high salt diet being used in the treatment of dysautonomia.[8]

Acute effects

Too much or too little salt in the diet can lead to muscle cramps, dizziness, or electrolyte disturbance, which can cause neurological problems, or death.[9] Drinking too much water, with insufficient salt intake, puts a person at risk of water intoxication (hyponatremia).[10]

Death can occur by ingestion of large amounts of salt in a short time (about 1 g per kg of body weight).[11] Deaths have also resulted from attempted use of salt solutions as emetics, forced salt intake, and accidental confusion of salt with sugar in child food.[12]

Long-term effects

The effect of high salt consumption on long term health outcomes is controversial.[13] Some associations include:

  • Stroke and cardiovascular disease.[14]
  • High blood pressure: Evidence shows an association between salt intakes and blood pressure among different populations and age range in adults.[15] Reduced salt intake also results in a small but significant reduction in blood pressure.[13][16]
  • Left ventricular hypertrophy (cardiac enlargement): "Evidence suggests that high salt intake causes left ventricular hypertrophy, a strong risk factor for cardiovascular disease, independently of blood pressure effects."[15] "...there is accumulating evidence that high salt intake predicts left ventricular hypertrophy."[17] Excessive salt (sodium) intake, combined with an inadequate intake of water, can cause hypernatremia. It can exacerbate renal disease.[9]
  • Edema: A decrease in salt intake has been suggested to treat edema (fluid retention).[9][18]
  • Stomach cancer is associated with high levels of sodium, "but the evidence does not generally relate to foods typically consumed in the UK."[19] However, in Japan, salt consumption is higher.[20]

However, a meta-analysis published in The Journal of Hypertension found no strong evidence that reducing salt intake affects the risk of heart attack, stroke or death in people with normal or high blood pressure.[21] Furthermore, the Journal of the American Medical Association has reported that those excreting less salt (thus, presumably ingesting less) were at increased risk of dying from heart disease.[21]

A salt mill for sea salt

In 1994, the British Medical Journal published a randomized double blind, placebo controlled study examining 100 Dutch middle-aged and elderly subjects with mild to moderate hypertension. A low sodium, high potassium, high magnesium mineral salt was used at the table and in foods given to the intervention group, with the control group using ordinary table salt in their foods and at the table. Over a 24-week period, the researchers found a reduced blood pressure in the intervention group, with mean blood pressure falling by 7.6 mm Hg (systolic) and 3.3 mm Hg (diastolic) in the mineral salt group compared with the control group.[22] However, critics have pointed out that it is possible that some of the subjects may have changed their dietary habits due to being able to distinguish the mineral salt from table salt because of the difference in taste.[23]

According to The Mayo Clinic and Australian Professor Bruce Neal, the health consequences of ingesting sea salt or regular table salt are the same, as the content of sea salt is still mainly sodium chloride.[24][25]

Recommended intakes of salt are usually expressed in terms of sodium intake. Salt (as sodium chloride) contains 39.3 percent of sodium by weight.

Country Description Sodium intake
mg per day 		Salt intake
mg per day 		Authority Remarks
United Kingdom The Reference Nutrient Intake (RNI) defined for a typical adult RNI: 1600 RNI: 4000 Scientific Advisory Committee on Nutrition (SACN) (2003)[26] However, average adult intake is two and a half times the RNI. SACN states, "The target salt intakes set for adults and children do not represent ideal or optimum consumption levels, but achievable population goals." The Food Safety Authority of Ireland endorses the UK targets.[17]
Canada An Adequate Intake (AI) and Upper Limit (UL) recommended for persons aged 9 years or more. AI: 1200–1500
UL: 2200–2300 		AI: 3000–3750
UL: 5500–5750 		Health Canada (2005)[27]
Australia and New Zealand An Adequate Intake (AI) and an Upper Level of intake (UL) defined for adults AI: 460–920
UL: 2300 		AI: 1150–2300
UL: 5750 		NHMRC (2006)[28] Not able to define a recommended dietary intake (RDI)
United States An Upper Limit (UL) defined for adults. A different upper limit defined for the special group comprising people over 51 years of age, African Americans and people with hypertension, diabetes, or chronic kidney disease (regardless of age). UL: 2300
UL for special group: 1500 		UL: 5750
UL for special group: 3750 		Department of Agriculture and Department of Health and Human Services (2010)[7][29][30] The Food and Drug Administration itself does not make a recommendation, but refers readers to the dietary guidelines given by this authority.[31]

As of 2009 sodium consumption in 33 countries was in the range of 2,700 to 4,900 mg/day. The small range across many cultures, together with animal studies, suggest that sodium intake is tightly controlled by feedback loops in the body, making recommendations to reduce sodium consumption below 2,700 mg/day potentially futile.[32] Upon review, an expert committee commissioned by the Institute of Medicine and the Centers for Disease Control and Prevention reported that there was no health outcome-based rationale for reducing daily sodium intake levels below 2,300 milligrams, as had been recommended by previous dietary guidelines; the report did not have a recommendation for an upper limit of daily sodium intake.[33][34]

Labeling

UK: The Food Standards Agency defines the level of salt in foods as follows: "High is more than 1.5 g salt per 100 g (or 0.6 g sodium). Low is 0.3 g salt or less per 100 g (or 0.1 g sodium). If the amount of salt per 100 g is in between these figures, then that is a medium level of salt." In the UK, foods produced by some supermarkets and manufacturers have 'traffic light' colors on the front of the pack: red (high), amber (medium), or green (low).[35]

USA: The FDA Food Labeling Guide stipulates whether a food can be labeled as "free" "low," or "reduced/less" in respect of sodium. When other health claims are made about a food (e.g., low in fat, calories, etc.), a disclosure statement is required if the food exceeds 480 mg of sodium per 'serving'.[36]

Campaigns

Consensus Action on Salt and Health (CASH)[37] established in the United Kingdom in 1996, actively campaigns to raise awareness of the harmful health effects of salt. The 2008 focus includes raising awareness of high levels of salt hidden in sweet foods that are marketed towards children.[38] In 2004, Britain's Food Standards Agency started a public health campaign called "Salt – Watch it", which recommends no more than 6g of salt per day; it features a character called Sid the Slug and was criticised by the Salt Manufacturers Association (SMA).[39] The Advertising Standards Authority did not uphold the SMA complaint in its adjudication.[40] In March 2007, the FSA launched the third phase of their campaign with the slogan "Salt. Is your food full of it?" fronted by comedienne Jenny Eclair.[41]

The University of Tasmania's Menzies Research Institute maintains a website to educate people about the problems of a salt-laden diet.[42] In Australia, the "Drop the Salt! Campaign" aimed to reduce the consumption of salt by Australians to 6g per day over the course of five years ending in 2012.[43]

In January 2010, New York City launched the National Salt Reduction Initiative, modeled after an initiative in the United Kingdom. The campaign calls on food makers to voluntarily reduce the amount of sodium in their foods, from 20 percent reduction in peanut butter to a 40 percent reduction in canned vegetables, with an overall goal of reducing sodium in packaged and restaurant foods by 25 percent by 2015.[44] A number of major food producers have taken up the challenge and pledged to reduce the sodium content of their food. Pepsi is developing a "designer salt" that's slightly more powdery than the salt it regularly uses. The company hopes this new form of salt will cut sodium levels by 25 percent in its Lay's potato chips.[45] Nestlé's prepared foods company, which produces frozen meals, announced that it will reduce sodium in its foods by 10 percent by 2015.[46] General Mills announced that it will reduce the sodium content of 40 percent of its foods by about 20 percent by 2015.[47]

In the United States, taxation of sodium has been proposed as a method of decreasing sodium intake and thereby improving health in countries where typical salt consumption is high.[48][49] Taking an alternative view, the Salt Institute, a salt industry body based in North America, is active in promoting the use of salt,[50] and questioning or opposing the recommended restrictions on salt intake.[51]

Lowering salt in diet

It is a misconception that sea salt has a lower sodium content than table salt — they are both basically sodium chloride.[24][52][53] A low sodium diet reduces the intake of sodium by the careful selection of food. This aim can also be achieved by the use of a salt substitute, and Potassium chloride is widely used for this purpose. Although recommended limits for potassium are higher than for sodium, potassium has its own health disadvantages, and it is advised that such a salt substitute not be used by those taking certain prescription drugs.[54] Another possibility being researched is the use of seaweed granules in the manufacture of processed foods as an alternative to salt.[55]

References

  1. ^ Caldwell, J. H.; Schaller, KL; Lasher, RS; Peles, E; Levinson, SR (2000). "Sodium channel Nav1.6 is localized at nodes of Ranvier, dendrites, and synapses". Proceedings of the National Academy of Sciences. 97 (10): 5616–5620. doi:10.1073/pnas.090034797. PMC 25877. PMID 10779552.
  2. ^ "American Heart Association 2010 Dietary Guidelines" (PDF). 2010 Dietary Guidelines. American Heart Association. 23 January 2009. Retrieved 16 May 2010.
  3. ^ "Nutrient Reference Values for Australia and New Zealand – Sodium". Nutrient Reference Values for Australia and New Zealand. Australian Government National Health and Medical Research Council/ New Zealand Ministry of Health. Retrieved 16 May 2010.
  4. ^ "Dietary Guidelines focus on sodium intake, sugary drinks, dairy alternatives". Food Navigator-usa.com. Decision News Media. 27 April 2010. Retrieved 16 May 2010.
  5. ^ "Sodium Chloride". Eat Well, Be Well. UK Government Food Standards Agency. Retrieved 16 May 2010.
  6. ^ "Health Canada, Healthy Living, Sodium". Healthy Living. Health Canada. 2008. Retrieved 16 May 2010.
  7. ^ a b "Dietary Guidelines for Americans 2010" (PDF). US Department of Agriculture and US Department of Health and Human Services. Retrieved 27 February 2012.
  8. ^ Cleveland Clinic Health Information Center Dysautonomia page. Clevelandclinic.org. Retrieved 7 July 2011.
  9. ^ a b c Salt Australia: Better Health Channel (Australia, Victoria). Betterhealth.vic.gov.au. Retrieved 7 July 2011.
  10. ^ "Hyponatremia ("Water Intoxication")". The DEA.org. Retrieved 7 March 2013.
  11. ^ Safety data for sodium chloride The Physical and Theoretical Chemistry Laboratory of Oxford University (18 November 2005). Retrieved 7 July 2011.
  12. ^ Turk, E; Schulz, F; Koops, E; Gehl, A; Tsokos, M (2005). "Fatal hypernatremia after using salt as an emetic?report of three autopsy cases". Legal Medicine. 7 (1): 47–50. doi:10.1016/j.legalmed.2004.06.005. PMID 15556015. {{cite journal}}: Invalid |ref=harv (help)
  13. ^ a b Dumler, F (January 2009). "Dietary sodium intake and arterial blood pressure". Journal of renal nutrition : the official journal of the Council on Renal Nutrition of the National Kidney Foundation. 19 (1): 57–60. doi:10.1053/j.jrn.2008.10.006. PMID 19121772.
  14. ^ Strazzullo P, D'Elia L, Kandala NB, Cappuccio FP (2009). "Salt intake, stroke, and cardiovascular disease: meta-analysis of prospective studies". BMJ. 339: b4567. doi:10.1136/bmj.b4567. PMC 2782060. PMID 19934192. {{cite journal}}: Invalid |ref=harv (help)CS1 maint: multiple names: authors list (link)
  15. ^ a b Scientific Advisory Committee on Nutrition (SACN) Salt and Health, page 3
  16. ^ He, FJ (2013 Apr 3). "Effect of longer term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomised trials". BMJ (Clinical research ed.). 346: f1325. PMID 23558162. {{cite journal}}: Check date values in: |date= (help); Unknown parameter |coauthors= ignored (|author= suggested) (help)
  17. ^ a b Food Safety Authority of Ireland Salt and Health: Review of the Scientific Evidence and Recommendations for Public Policy in Ireland, p. 12
  18. ^ Australia: Better Health Channel (Australia, Victoria) Fluid retention
  19. ^ Scientific Advisory Committee on Nutrition (SACN) Salt and Health, page 18
  20. ^ Salt raises 'stomach cancer risk', BBC News Online, 7 January 2004
  21. ^ a b Wenner Moyer, Melinda (8 July 2011). "It's Time to End the War on Salt". Scientific American. Retrieved 23 December 2012.
  22. ^ Geleijnse JM, Witteman JC, Bak AA, den Breeijen JH, Grobbee DE (1994). "Reduction in blood pressure with a low sodium, high potassium, high magnesium salt in older subjects with mild to moderate hypertension". BMJ. 309 (6952): 436–40. doi:10.1136/bmj.309.6952.436. PMC 2540967. PMID 7920126. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  23. ^ Fielder H, Lo SV (1994). "Effect of dietary mineral salt on blood pressure. Study methods flawed". BMJ. 309 (6962): 1157. doi:10.1136/bmj.309.6962.1157a. PMC 2541910. PMID 7987117. {{cite journal}}: Unknown parameter |month= ignored (help)
  24. ^ a b Zeratsky, Katherine (27 August 2009). "Is sea salt better for your health than table salt?". Mayo Foundation for Medical Education and Research. Retrieved 22 April 2011.
  25. ^ Australian Broadcasting Corporation – Health and Wellbeing (23 November 2010) – Rae Fry and Professor Bruce Neal – Retrieved 23 November 2010
  26. ^ Scientific Advisory Committee on Nutrition (SACN) Salt and Health
  27. ^ Health Canada Dietary Reference Intakes
  28. ^ NHMRC Reference Nutrient Values, Sodium
  29. ^ Zied, Elisa (31 January 2011). "New U.S. Dietary Guidelines Focus on Salt Reduction". U.S. News & World Report.
  30. ^ Gardner, Amanda (31 January 2011). "Hold the salt! New food rules lower sodium limits". MSNBC.
  31. ^ Alexandra Greeley A Pinch of Controversy Shakes Up Dietary Salt. US Food and Drug Administration
  32. ^ McCarron, D. A.; Geerling, J. C.; Kazaks, A. G.; Stern, J. S. (2009). "Can Dietary Sodium Intake Be Modified by Public Policy?". Clinical Journal of the American Society of Nephrology. 4 (11): 1878–82. doi:10.2215/CJN.04660709. PMID 19833911. {{cite journal}}: Invalid |ref=harv (help)
  33. ^ Kolata, Gina (14 May 2013). "No Benefit Seen in Sharp Limits on Salt in Diet". New York Times. Retrieved 3 June 2013.
  34. ^ Strom, Brian (2013). Sodium Intake in Populations: Assessment of Evidence. Washington, DC: The National Academies Press: The Institute of Medicine.
  35. ^ Understanding labels. Salt.gov.uk (6 November 2009). Retrieved 7 July 2011.
  36. ^ Food and Drug Administration A Food Labeling Guide—Appendix A
  37. ^ "CASH: Consensus Action on Salt and Health". Retrieved 7 March 2013.
  38. ^ Smithers, Rebecca (28 January 2008). "Child health fears over high salt levels in sweet foods". The Guardian. London. Retrieved 23 May 2010.
  39. ^ Salt Manufacturers Association press release New salt campaign under attack
  40. ^ Advertising Standards Authority Broadcast Advertising Adjudications: 20 April 2005 (PDF)
  41. ^ Salt TV ads. Salt.gov.uk (6 November 2009). Retrieved 7 July 2011.
  42. ^ Dr Trevor Beard (26 March 2009). "Salt Matters". University of Tasmania. Retrieved 17 May 2010.
  43. ^ "Drop the Salt! Campaign". Australian Division on World Action on Salt & Health. Retrieved 7 March 2013.
  44. ^ Caruso, David B (15 January 2010). "NYC asks food manufacturers to cut salt content". USA Today. Associated Press.
  45. ^ McKay, Betsy (22 March 2010). "PepsiCo Develops 'Designer Salt' to Chip Away at Sodium Intake". The Wall Street Journal.
  46. ^ Nestle Prepared Foods Company to Decrease Sodium by Another 10% by 2015", Prnewswire
  47. ^ Scott-Thomas, Caroline, "General Mills announces sodium reduction strategy," Food Navigator, 14 April 2010.
  48. ^ Wilson, N (2004). "Salt tax could reduce population's salt intake". BMJ. 329 (7471): 918. doi:10.1136/bmj.329.7471.918-c. PMC 523164. PMID 15485985. {{cite journal}}: Unknown parameter |month= ignored (help)
  49. ^ "Salt tax could massively reduce US mortality rates, healthcare costs". 11 March 2010.
  50. ^ "About the Salt Institute". Salt Institute. 2009. Retrieved 5 December 2010.
  51. ^ "Food salt & health". Salt Institute. 2009. Retrieved 5 December 2010.
  52. ^ Australian Broadcasting Corporation – Health and Wellbeing (23 November 2010) – Neal, Bruce – Retrieved 24 May 2012
  53. ^ Survey Shows Many People Have Misconceptions About Red Wine, Sea Salt. Dr. Cutler (27 April 2011). Retrieved 5 May 2011.
  54. ^ LoSalt Advisory Statement (PDF)
  55. ^ Daniells, Stephen (2008-09-23). "Seaweed granules may replace salt in foods". FoodNavigator.com. Retrieved 2013-02-07.
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