The kidneys regulate levels of sodium in the body. When sodium levels are low, the kidneys work to conserve sodium. When sodium levels are high, excess sodium passes from the body through urine, and to a lesser extent, through perspiration.

However, a person with damaged kidneys or other conditions (including congestive heart failure and the liver disease cirrhosis) may not be able to eliminate excess sodium, allowing it to build up in the blood. Too much salt can lead to water retention in the blood, because sodium attracts and holds water.

Normally, the kidneys flush excess water from the body. However, kidneys that are not functioning properly are unable to expel the excess fluid sufficiently, leading to fluid retention. This increases the volume of blood being pumped through the blood vessels and can lead to high blood pressure (hypertension).

In an effort to pump the extra fluid through the body, the heart may become enlarged. The extra volume of fluid may also leave the bloodstream and enter body tissues, causing swelling (edema) in the parts of the body where it builds up.

Certain people have a greater sensitivity to high levels of sodium than others. Up to 30 percent of Americans have blood pressure that is sensitive to sodium, according to the American Dietetic Association. Patients with this condition may experience a spike in blood pressure after consuming too much sodium. Research has shown that African Americans tend to be more salt-sensitive than white Americans.

Studies have not identified whether people are genetically predisposed to be salt-sensitive. However, it is known that reducing sodium consumption can help lower blood pressure in salt-sensitive patients. There is no test to indicate whether or not a person’s blood pressure is sodium-sensitive. Therefore, some patients with high-sodium diets will develop high blood pressure, while others will not.

The National Heart, Lung and Blood Institute (NHLBI) released clinical practice guidelines for the prevention, detection and treatment of high blood pressure in 2003. The report recommends and encourages lifestyle changes to prevent high blood pressure. These include losing excess weight, becoming physically active, limiting alcoholic beverages and following a heart-healthy diet, including cutting back on salt and other forms of sodium.

The guidelines recommend that people follow the Dietary Approach to Stop Hypertension (DASH) eating plan, which is rich in fruits, vegetables, lowfat dairy products and low in saturated fat, total fat, and cholesterol. It is also high in fiber. In addition to reducing levels of salt and sodium, the DASH diet includes generous helpings of other minerals that also may help lower blood pressure. This includes potassium from fruits and vegetables, calcium from dairy foods and certain vegetables and magnesium from whole grains, legumes, nuts and green vegetables.

Other studies have suggested that lower salt intake may reduce the risk of high blood pressure, heart disease, heart failure and stroke in overweight men and women. Research indicates that lower levels of salt may help reduce calcium loss from bone, which in turn reduces the risk of osteoporosis and bone fractures. In addition, reducing sodium may help a person lose weight. Sodium both attracts and holds water. People who eat less salt retain less water and are not as bloated.

One recent study even linked salt intake and obesity. Researchers reported that consuming higher levels of sodium increases thirst. Many Americans slake their thirst by drinking beverages high in calories, which in turn causes weight gain.

Although a low-salt diet benefits the health of most people, pregnant women should not cut back on sodium. Pregnant women generally need more sodium then women who are not pregnant, although this usually can be obtained in a balanced prepregnancy eating plan.