Salt and health

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Chloride and sodium ions, the two major components of salt, are necessary for the survival of all creatures, including humans. Salt is involved in regulating the water content (fluid balance) of the body. Sodium is one of the primary electrolytes in the body.

Some isolated cultures, such as the Yanomami in South America, have been found to consume little salt, possibly an adaptation originated in the predominantly vegetarian diet of human primate ancestors.[1]

Salt-related conditions

Too much or too little salt in the diet can lead to muscle cramps, dizziness, or even an electrolyte disturbance, which can cause severe, even fatal, neurological problems.[2]

Excess salt consumption has been linked to:

  • exercise-induced asthma.[3] On the other hand, another source counters, "…we still don't know whether salt contributes to asthma. If there is a link then it's very weak…".[4]
  • heartburn[5].
  • osteoporosis: One report shows that a high salt diet does reduce bone density in girls.[6]. Yet "While high salt intakes have been associated with detrimental effects on bone health, there are insufficient data to draw firm conclusions." ([7], p3)
  • Gastric cancer (Stomach cancer) is associated with high levels of sodium, "but the evidence does not generally relate to foods typically consumed in the UK." ([7], p18) However, in Japan, salt consumption is higher.[8]
  • hypertension (high blood pressure): "Since 1994, the evidence of an association between dietary salt intakes and blood pressure has increased. The data have been consistent in various study populations and across the age range in adults." ([7] p3). A large scale study from 2007 has shown that people with high-normal blood pressure who significantly reduced the amount of salt in their diet decreased their chances of developing cardiovascular disease by 25% over the following 10 to 15 years. Their risk of dying from cardiovascular disease decreased by 20%.[9]
  • 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." ([7] p3) "…there is accumulating evidence that high salt intake predicts left ventricular hypertrophy." ([10], p12) Excessive salt (sodium) intake, combined with an inadequate intake of water, can cause hypernatremia. It can exacerbate renal disease.[2]
  • edema (BE: oedema): A decrease in salt intake has been suggested to treat edema (fluid retention).[11][2]
  • duodenal ulcers and gastric ulcers[12]

Ingestion of large amounts of salt in a short time (about 1 g per kg of body weight) can be fatal through hypernatremia.[2] Salt solutions have been used in China as a traditional suicide method, and 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.[13]

Salt is sometimes used as a health aid, such as in treatment of dysautonomia.[14]

Recommended intake

This section summarizes the salt intake recommended by the health agencies of various countries. Recommendations tend to be similar. Note that targets for the population as a whole tend to be pragmatic (what is achievable) while advice for an individual is ideal (what is best for health). For example, in the UK target for the population is "eat no more than 6 g a day" but for a person is 4 g.

Intakes can be expressed variously as salt or sodium and in various units.

  • 1 g sodium = 1,000 mg sodium = 42 mmol sodium = 2.5 g salt

United Kingdom: In 2003, the UK's Scientific Advisory Committee on Nutrition (SACN) recommended that, for a typical adult, the Reference Nutrient Intake is 4 g salt per day (1.6 g or 70 mmol sodium). However, average adult intake is two and a half times the Reference Nutrient Intake for sodium. "Although accurate data are not available for children, conservative estimates indicate that, on a body weight basis, the average salt intake of children is higher than that of adults." SACN aimed for an achievable target reduction in average intake of salt to 6 g per day (2.4 g or 100 mmol sodium) — this is roughly equivalent to a teaspoonful of salt. The SACN recommendations for children are:

  • 0–6 months old: less than 1 g/day
  • 7–12 months: 1 g/day
  • 1–3 years: 2 g/day
  • 4–6 years: 3 g/day
  • 7–10 years: 5 g/day
  • 11–14 years: 6 g/day

SACN states, "The target salt intakes set for adults and children do not represent ideal or optimum consumption levels, but achievable population goals."[7]

Republic of Ireland: The Food Safety Authority of Ireland endorses the UK targets "emphasising that the RDA of 1.6 g sodium (4 g salt) per day should form the basis of advice targeted at individuals as distinct from the population health target of a mean salt intake of 6 g per day."([10], p16)

Canada: Health Canada recommends an Adequate Intake (AI) and an Upper Limit (UL) in terms of sodium.

  • 0–6 months old: 0.12 g/day (AI)
  • 7–12 months: 0.37 g/day (AI)
  • 1–3 years: 1 g/day (AI) 1.5 g/day (UL)
  • 4–8 years: 1.2/day (AI) 1.9 g/day (UL)
  • 9–13 years: 1.5 g/day (AI) 2.2 g/day (UL)
  • 14–50 years: 1.5 g/day (AI) 2.3 g/day (UL)
  • 51–70 years: 1.3 g/day (AI) 2.3 g/day (UL)
  • 70 years and older: 1.2 g/day (AI) 2.3 g/day (UL)[15]

New Zealand

  • Adequate Intake (AI) 0.46 – 0.92 g sodium = 1.2 – 2.3g salt
  • Upper Limit (UL)) 2.3 g sodium = 5.8 g salt[16]

Australia: The recommended dietary intake (RDI) is 0.92 g–2.3 g sodium per day (= 2.3 g–5.8 g salt)[17]

USA: The Food and Drug Administration itself does not make a recommendation[18] but refers readers to Dietary Guidelines for Americans 2005. These suggest that US citizens should consume less than 2,300 mg of sodium (= 2.3 g sodium = 5.8 g salt) per day. [19]

Labelling

UK: The Food Standards Agency defines the level of salt in foods as follows: "High is more than 1.5g salt per 100g (or 0.6g sodium). Low is 0.3g salt or less per 100g (or 0.1g sodium). If the amount of salt per 100g 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).[20]

USA: The FDA Food Labeling Guide stipulates whether a food can be labelled 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 480mg of sodium per 'serving.'[21]

Campaigns

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).[22] The Advertising Standards Authority did not uphold the SMA complaint in its adjudication.[23]. 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.[24]

The Menzies Research Institute in Tasmania, Australia, maintains a website [25] dedicated to educating people about the potential problems of a salt-laden diet.

Consensus Action on Salt and Health (CASH)[26] established 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 and marketed towards children.[27]

Additives to salt

Iodized salt

Iodized salt (BrE: iodised salt) is table salt mixed with a minute amount of potassium iodide, sodium iodide, or iodate. Iodized salt is used to help reduce the chance of iodine deficiency in humans. Iodine deficiency commonly leads to thyroid gland problems, specifically endemic goitre. Endemic goitre is a disease characterized by a swelling of the thyroid gland, usually resulting in a bulbous protrusion on the neck. While only tiny quantities of iodine are required in a diet to prevent goitre, the United States Food and Drug Administration recommends (21 CFR 101.9 (c)(8)(iv)) 150 micrograms of iodine per day for both men and women, and there are many places around the world where natural levels of iodine in the soil are low and the iodine is not taken up by vegetables.

Today, iodized salt is more common in the United States, Australia and New Zealand than in the United Kingdom. Table salt is also often iodized—a small amount of potassium iodide (in the US) or potassium iodate (in the EU) is added as an important dietary supplement. Table salt is mainly employed in cooking and as a table condiment. Iodized table salt has significantly reduced disorders of iodine deficiency in countries where it is used.[28] Iodine is important to prevent the insufficient production of thyroid hormones (hypothyroidism), which can cause goitre, cretinism in children, and myxedema in adults.

The amount of iodine and the specific iodine compound added to salt varies from country to country. In the United States, iodized salt contains 46-77 ppm, while in the UK the iodine content of iodized salt is recommended to be 10-22 ppm.[29]

Some advocates for sea salt assert that unrefined sea salt is more healthy than refined salts.[30] However, completely raw sea salt is bitter due to magnesium and calcium compounds, and thus is rarely eaten. The refined salt industry cites scientific studies saying that raw sea and rock salts do not contain enough iodine salts to prevent iodine deficiency diseases.[31]

Other additives

In some European countries where drinking water fluoridation is not practised, fluorinated table salt is available.

Another additive, principally for pregnant women, is Folic acid (Vitamin B9), which gives the table salt a yellow colour.

Salt substitutes

Salt intake can be reduced by simply reducing the quantity of salty foods in a diet, without recourse to salt substitutes. Salt substitutes have a taste similar to table salt and contain mostly potassium chloride, which will increase potassium intake. Excess potassium intake can cause hyperkalemia. Various diseases and medications may decrease the body's excretion of potassium, thereby increasing the risk of hyperkalemia. If you have kidney failure, heart failure or diabetes, seek medical advice before using a salt substitute. A manufacturer, LoSalt, has issued an advisory statement[32] that people taking the following prescription drugs should not use a salt substitute: Amiloride, Triamterene, Dytac, Spironolactone (Brand name Aldactone), Eplerenone and Inspra.

Further reading

  • Department of Health, Dietary Reference Values for Food Energy and Nutrients for the UK: Report of the Panel on DRVs of the Committee on the Medical Aspects of Food Policy , The Stationery Office.
  • MacGregor G. A and de Wardener H. E. Salt, Diet and Health: Neptune's Poisoned Chalice: the Origins of High Blood Pressure Cambridge University Press; (1998) ISBN-10: 0521635454 ISBN-13: 978-0521635455

References

  1. ↑ Yanomami Indians in the INTERSALT study, (accessed13 January,2007)
  2. ↑ 2.0 2.1 2.2 2.3 Australia: Better Health Channel (Australia, Victoria) Salt
  3. ↑ Exercise-induced asthma more clearly linked to high-salt diet
  4. ↑ Dr Trisha Macnair "Does eating salt make asthma worse?"
  5. ↑ Everybody Study adds salt to suspected triggers for heartburn
  6. ↑ High salt diet reduces bone density in girls
  7. ↑ 7.0 7.1 7.2 7.3 7.4 Scientific Advisory Committee on Nutrition (SACN) Salt and Health (PDF)
  8. ↑ Salt raises 'stomach cancer risk'
  9. ↑ Cook NR, Cutler JA, Obarzanek E et. al. Long term effects of dietary sodium reduction on cardiovascular disease outcomes: observational follow-up of the trials of hypertension prevention (TOHP). BMJ. 2007;334(7599):885. PMID 17449506 Free full-text
  10. ↑ 10.0 10.1 Food Safety Authority of Ireland Salt and Health: Review of the Scientific Evidence and Recommendations for Public Policy in Ireland
  11. ↑ Australia: Better Health Channel (Australia, Victoria) Fluid retention
  12. ↑ BBC High-salt diet link to ulcer risk 22 May 2007
  13. ↑ Elisabeth Elena Türk, Friedrich Schulz, Erwin Koops, Axel Gehl and Michael Tsokos. Fatal hypernatremia after using salt as an emetic—report of three autopsy cases. Legal Medicine 2005, 7, 47-50. DOI:10.1016/j.legalmed.2004.06.005
  14. ↑ Cleveland Clinic Health Information Center Dysautonomia page
  15. ↑ Health Canada Dietary Reference Intakes (look for Sodium)
  16. ↑ Auckland District Health Board Public Health Nutrition Advice (PDF)
  17. ↑ Better Health Channel (Australia, Victoria) Salt
  18. ↑ U. S. Food and Drug Administration A Pinch of Controversy Shakes Up Dietary Salt
  19. ↑ Department of Health and Human Services (HHS) and the Department of Agriculture (USDA) Dietary Guidelines for Americans 2005 "Sodium and Potassium"
  20. ↑ Understanding labels
  21. ↑ Food and Drug Administration A Food Labeling Guide--Appendix A
  22. ↑ Salt Manufacturers Association press release New salt campaign under attack
  23. ↑ Advertising Standards Authority Broadcast Advertising Adjudications: 20 April 2005 (PDF)
  24. ↑ Salt TV ads
  25. ↑ Salt Matters
  26. ↑ CASH Consensus Action on Salt.
  27. ↑ My Blood Pressure.
  28. ↑ Iodized Salt
  29. ↑ Iodized Salt
  30. ↑ Susan Dearing Sea Salt is good for you and is made in Colima!
  31. ↑ Iodine in non-iodized sea salt
  32. ↑ LoSalt Advisory Statement (PDF)

External links

Government bodies

Many other government bodies are listed in the References section above.

Medical authorities

Charities and campaigns

Journalism

Salt industry

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