Does Decreasing Sodium Intake Increase Hydration?

Sodium and water are the most important components of human hydration. Sodium is what maintains the water balance within cells. Hydration is simply the introduction of additional fluid into the body. Sodium intake can influence dehydration.

Sodium Intake

Sodium and salt are not the same thing; table salt is 40 percent sodium and 60 percent chloride. Many foods naturally contain some sodium, and people can also increase sodium intake by salting their food. The recommended sodium intake is about 1,500 mg a day, less than a teaspoon of salt, while the maximum recommended intake is 2,300 mg a day. Most Americans consume the maximum recommended amount or more, so low sodium intake is not usually a problem.

Sodium and Water in the Body

Decreasing your sodium intake does not increase hydration. The mechanisms that control water in the body are not triggered by sodium. Instead, a hormone called vasopressin is used to make the kidneys control water excretion or retention. Vasopressin is released or suppressed in response to signals such as increasing plasma concentration, a high volume of blood returning to the heart or a fall in blood pressure.

Sodium and Osmolarity

What sodium can affect is the osmolarity of body fluids. Osomolarity refers to the amount of substances dissolved in a fluid. Sodium is the major substance dissolved in body fluids, so it effectively controls osmolarity. If you are dehydrated, you lose more water than sodium, so the body corrects this situation by conserving water, but not sodium. Even if you eat less salt, as long as you are healthy, your body will maintain the correct balance of water.

Restricting Sodium Intake

According to the Mayo Clinic, you may need to restrict your sodium intake if you have heart failure. However, a study reported in the December 2009 "Journal of Heart Failure" says that severe restriction of sodium intake actually led to dehydration in patients with heart failure. Moderate sodium restriction, defined as slightly more than the sodium in 1 tsp. of salt, helped patients maintain weight and improved patient outcomes.

Water and Sodium Intake

The Institute of Medicine recommends women drink a total of 91 fluid oz. and men drink 125 fluid oz. of water a day to assure proper hydration. This can be plain bottled or tap water, water from foods and other beverages such as coffee, tea or milk. Your salt intake should meet the recommended amounts, but if you have a medical condition such as heart failure or have questions or concerns, consult a health-care professional.