Salt in food

Salt is present in most foods, but in naturally occurring foodstuffs such as meats, vegetables and fruit, it is present in very small quantities. It is often added to processed foods (such as canned foods and especially salted foods, pickled foods, and snack foods or other convenience foods), where it functions as both a preservative and a flavoring. Dairy salt is used in the preparation of butter and cheese products. Before the advent of electrically powered refrigeration, salting was one of the main methods of food preservation. Thus, herring contains 67 mg sodium per 100 g, while kipper, its preserved form, contains 990 mg. Similarly, pork typically contains 63 mg while bacon contains 1,480 mg, and potatoes contain 7 mg but potato crisps 800 mg per 100 g. The main sources of salt in the diet, apart from direct use of sodium chloride, are bread and cereal products, meat products and milk and dairy products.

In many East Asian cultures, salt is not traditionally used as a condiment. In its place, condiments such as soy sauce, fish sauce and oyster sauce tend to have a high sodium content and fill a similar role to table salt in western cultures. They are most often used for cooking rather than as table condiments.

Sodium consumption and health

Table salt is made up of just under 40% sodium by weight, so a 6 g serving (1 teaspoon) contains about 2,300 mg of sodium. Sodium serves a vital purpose in the human body: via its role as an electrolyte, it helps nerves and muscles to function correctly, and it is one factor involved in the osmotic regulation of water content in body organs (fluid balance). Most of the sodium in the Western diet comes from salt. The habitual salt intake in many Western countries is about 10 g per day, and it is higher than that in many countries in Eastern Europe and Asia.[57] The high level of sodium in many processed foods has a major impact on the total amount consumed. In the United States, 75% of the sodium eaten comes from processed and restaurant foods, 11% from cooking and table use and the rest from what is found naturally in foodstuffs.

Because consuming too much salt increases risk of cardiovascular diseases, health organizations generally recommend that people reduce their dietary intake of salt.High salt intake is associated with a greater risk of stroke, total cardiovascular disease and kidney disease. A reduction in sodium intake by 1,000 mg per day may reduce cardiovascular disease by about 30 percent. In adults and children with no acute illness, a decrease in the intake of sodium from the typical high levels reduces blood pressure. A low salt diet results in a greater improvement in blood pressure in people with hypertension.

The World Health Organization recommends that adults should consume less than 2,000 mg of sodium (which is contained in 5 g of salt) per day. Guidelines by the United States recommend that people with hypertension, African Americans, and middle-aged and older adults should limit consumption to no more than 1,500 mg of sodium per day and meet the potassium recommendation of 4,700 mg/day with a healthy diet of fruits and vegetables. 

While reduction of salt intake to less than 2,300 mg per day is recommended by developed countries,one review recommended that salt intake be no less than 1,200 mg (contained in 3 g) per day, as it is an essential nutrient required from the diet. Another review indicated that reducing sodium intake to lower than 2,300 mg per day may not be beneficial.One of the two most prominent dietary risks for disability in the world is eating too much salt.

Acute effects

Hypernatremia, a blood sodium level above 145 mEq/L, causes thirst, and due to brain cell shrinkage may cause confusion, muscle twitching or spasms. With severe elevation, seizures and comas may occur.Death can be caused by ingestion of large amounts of salt at a time (about 1 g per kg of body weight). Deaths have also been caused by use of salt solutions as emetics (typically after suspected poisoning), forced salt intake, and accidental use of salt instead of similar-looking sugar in food.

Hyponatremia, or blood sodium levels below 135 mEq/L, causes brain cells to swell; the symptoms can be subtle and may include altered personality, lethargy, and confusion. In severe cases, when blood sodium falls below 115 mEq/L, stupor, muscle twitching or spasms, seizures, coma, and death can result.Acute hyponatremia is usually caused by drinking too much water, with insufficient salt intake.

The health effects of salt are the conditions associated with the consumption of either too much or too little salt. Salt is a mineral composed primarily of sodium chloride (NaCl) and is used in food for both preservation and flavor. Sodium ions are needed in small quantities by most living things, as are chloride ions. 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.

Salt consumption has increased during modern times. Scientists have become aware of health risks associated with high salt intake, including high blood pressure in sensitive individuals. Therefore, health authorities recommend limitations on dietary sodium.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.As an essential nutrient, sodium is involved in numerous cellular and organ functions. Salt intake that is too low may also increase risk for cardiovascular disease and early death.

Long-term effects

Although many health organizations and recent reviews state that high consumption of salt increases the risk of several diseases in children and adults, the effect of high salt consumption on long term health is controversial. Some suggest that the effects of high salt consumption are insignificant.Sodium intake is well known to be associated with increased blood pressure, particularly in sensitive populations. Most studies suggest a "U" shaped association between salt intake and health, with increased mortality associated with both excessively low and excessively high salt intake.

Health effects associated with excessive sodium consumption include:

  • Stroke and cardiovascular disease.
  • High blood pressure: Evidence shows an association between salt intakes and blood pressure among different populations and age range in adults.Reduced salt intake also results in a small but statistically significant reduction in blood pressure.
  • Left ventricular hypertrophy (cardiac enlargement): "Evidence suggests that high salt intake causes left ventricular hypertrophy. This is a strong risk factor for cardiovascular disease, independently of blood pressure effects.there is accumulating evidence that high salt intake can predicts left ventricular hypertrophy."Excessive salt (sodium) intake, combined with an inadequate intake of water, can cause hypernatremia. It can exacerbate renal disease.
  • Edema: A decrease in salt intake has been suggested to treat edema (fluid retention).
  • Stomach cancer is associated with high levels of sodium, "but the evidence does not generally relate to foods typically consumed in the UK.However, in Japan, salt consumption is higher.
  • Kidney disease: A US expert committee reported in 2013 the common recommendation by several authorities "to reduce daily sodium intake to less than 2,300 milligrams and further reduce intake to 1,500 mg among persons who are 51 years of age and older and those of any age who are African-American or have hypertension, diabetes, or chronic kidney disease", but concluded that there was no health-outcome-based rationale for reducing intake below 2,300 mg, 

One report stated that people excreting less salt (thus, presumably ingesting less) were at increased risk of dying from heart disease. However, a recent meta-analysis conducted by the Cochrane Hypertension group found this article was subject to methodological flaws, and urges great caution when interpreting their results.

Another meta-analysis investigated the association between sodium intake and health outcomes, including all-cause mortality and cardiovascular disease (CVD) events.Sodium intake level was a mean of <115 115-215="" a="" and="" high="" intake="" mg="" mmol="" nbsp="" sodium="" usual="" was="">215 mmol (4945 mg), concluding: "Both low sodium intakes and high sodium intakes are associated with increased mortality, consistent with a U-shaped association between sodium intake and health outcomes".