Sodium: Too Much of a Good Thing

Why do we need sodium?

It is often said that our need for salt (sodium chloride) is the result of animal life on earth having initially developed in the sea. Regardless of how we acquired our need for sodium, it is one of many substances that our bodies need to function properly. The human body works hard to keep its serum concentration of sodium within a narrow range (135–145 mmol/L). It does so mostly by controlling the balance of sodium and water in the urine.

What causes high sodium levels?

Most of us know that eating too much salt is bad – especially for people with high blood pressure. But not everyone knows that salt can be poisonous. Taking in too much sodium can overwhelm our backup systems and cause dangerous increases in sodium concentrations. This is true whether we take it all at once, or if we take in large amounts over a period of days or weeks.

A high sodium concentration in the body is usually the result of excess sodium consumption, inadequate water intake, or both. Excess sodium consumption can be intentional or unintentional. This can mean eating ordinary table salt, rock salt, or high-sodium foods. 

Sodium poisoning can occur in a variety of ways. Long ago, salt water was used to make people vomit after poisoning. However, this dangerous "treatment" has been fatal. In other cases, people who experience mental illness have eaten large amounts of salt or given large amounts to their children. In one case, a man drank a salt solution intended as mouthwash. Infants have been known to be poisoned when salt is mistaken for sugar in formula. 

Dehydration can cause high sodium concentrations. This can happen because someone does not have access to water or fails to respond to the body’s thirst signals, or because of excessive water loss through sweating (from high fever or high heat), vomiting, or diarrhea. There are some rare medical conditions that can cause sodium concentrations to get too high.

What are the symptoms of sodium poisoning?

Too much sodium can have dangerous, or even fatal, effects. When there is too much sodium in the bloodstream, water is pulled out of our cells to dilute it. That is damaging to most cells, and devastating to brain cells. As the brain cells shrink, they are torn away from their usual locations, which can tear blood vessels and build up fluid in the brain, causing seizures and coma. Fluid can also build up in the lungs, causing trouble breathing. Other symptoms include intense thirst, nausea, vomiting, and weakness. Kidney damage can also occur.

How much sodium should you have per day?

The daily maximum sodium intake considered healthy for adults is about 2300 mg/day.

What foods contain high levels of sodium?

The typical American diet is loaded with sodium. Table salt is the most obvious source of sodium, but an estimated 70% of dietary sodium comes from eating packaged and processed foods. The Nutrition Facts label on a food product includes its sodium content. Looking at these labels makes it obvious that many foods are packed with sodium. A food product does not need to have an obvious salty taste to contain a lot of sodium. 

Omitting table salt is a good first step toward reducing sodium consumption, but it is easy to exceed the daily limit just by eating packaged foods. A tablespoonful of soy sauce can contain up to 1000 mg of sodium. Other major offenders include processed meats, pizza, soups, and snacks like chips and crackers.

Most people will not eat too much salt or drink very salty liquids because it tastes bad and makes them very thirsty. That might not stop people who cannot tell what they are doing, such as people experiencing dementia or other mental illnesses.

Suspect a sodium poisoning? Here’s what to do.

If you think someone has swallowed too much salt, give water if awake and breathing okay. Call 911 if the person won't wake up, is not breathing, or is having seizures. In any case, use the webPOISONCONTROL online tool for guidance or call Poison Control at 1-800-222-1222. The experts will tell you what to do right away.

Rose Ann Gould Soloway, RN, BSN, MSEd, DABAT emerita
Clinical Toxicologist

Revised William G. Troutman, PharmD
Professor of Pharmacy Emeritus

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