Health effects of salt

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 chlorine ions. Salt is involved in regulating the water content (fluid balance) of the body. Both sodium and chlorine ions are used for electrical signaling in the nervous system, among other biological roles.

Salt is usually high in ultra-processed and hyperpalatable foods. In 2020, the World Health Organization (WHO) recommended that adults consume no more than 5 grams (0.18 oz) (just under a teaspoon) of salt per day, an amount providing about 2 grams (0.071 oz) of sodium per day. The WHO further recommends that salt intake be adjusted for those aged 2 to 15 years old based on their energy requirements relative to those of adults. High sodium consumption (5 g or more of salt per day) and insufficient potassium intake (less than 3.5 grams (0.12 oz) per day) have been linked to high blood pressure and increased risk of heart disease, stroke, and kidney disease.

As an essential nutrient, sodium is involved in numerous cellular and organ functions. Several national health organizations recommend limiting sodium consumption to 2.3 g per day. However, some studies have found that sodium intake that is below 3 g per day (equivalent to about 7.5 g of salt) may increase the risk for cardiovascular disease and early death. The cardiovascular benefits of reducing salt consumption are similar to population-wide reductions in obesity, cholesterol, and tobacco use.

Hypernatremia (high 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 the use of salt solutions as emetics, typically after suspected poisoning.

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.

Major health organizations and recent reviews state that high consumption of salt increases the risk of several diseases in children and adults.

Excess sodium consumption increases blood pressure. Approximately 15% of adults have inverse salt sensitivity, with blood pressure increasing from eating less salt. Some studies suggest a U-shaped association between salt intake and mortality, with increased mortality associated with both excessively low and excessively high salt intake. Larger reductions in salt intake lead to larger decreases in blood pressure.

Normotensive overweight/obese patients who were salt restricted for six weeks showed an endothelin 1 (ET-1) decrease of 14% associated with a 45% increase in flow-mediated dilation (FMD). ET-1 has autocrine action on endothelial cells causing the release of nitric oxide. Another study using middle-aged or older adults with moderately elevated blood pressure taking sodium chloride tablets or placebo tablets for a few weeks showed that sodium restriction increased nitric oxide and tetrahydrobiopterin (BH4) resulting in improved FMD without affecting blood pressure. The suppression of endothelium production of nitric oxide is the result of oxidative stress on the vasculature.