The most significant consequence that excess salt has on the heart is high blood pressure (hypertension). Too much salt can lead to water retention in the blood. Normally, the kidneys flush this excess water from the body. However, kidneys that are not functioning properly are unable to expel the excess fluid sufficiently, which will lead to fluid retention. This increases the volume of blood being pumped through the blood vessels and can lead to high blood pressure.

In an effort to pump the extra fluid through the body, the heart may also become dilated or 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. 

If an individual already has high blood pressure, kidney function may slow down and excess salt and fluid will collect in the body, adding further to the hypertension problem. Hypertension is a risk factor for heart attacks, kidney disease and strokes.

The National Heart, Lung and Blood Institute (NHLBI) clinical practice guidelines recommend and encourage 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 Americans follow the Dietary Approach to Stop Hypertension (DASH) eating plan, rich in fruits, vegetables and nonfat dairy products.

Although sometimes controversial, the long-standing argument against the excessive use of salt has gained strength over the last several years. Studies have indicated that higher salt intake increases an individual’s blood pressure. In turn, higher blood pressure is linked to an increased risk of coronary heart disease, stroke and congestive heart failure. By reducing salt intake, individuals may prevent of reduce the onset of high blood pressure and associated medical conditions.

Other studies have suggested that salt intake increases the risk not only of high blood pressure, but also of heart disease, heart failure and stroke in overweight men and women. In addition, studies have suggested that people with salt- sensitivity (a measure of blood pressure change in response to salt intake) have a greater risk of medical problems with high salt consumption.

Research has shown that African Americans tend to be more salt-sensitive than white Americans, and as many as 80 percent of African Americans with high blood pressure may be salt-sensitive. While these studies have not identified whether people are genetically predisposed to be salt-sensitive, they have shown that all individuals will positively benefit from a reduced-salt diet.

About 75 percent of all salt consumed in the United States comes from salt added in the processing and manufacturing of foods. Only 12 percent of salt in the average occurs naturally in foods.

The amount of sodium found in foods in the American diet varies according to the specific item. Certain foods typically have higher sodium content due to their preparation. For example, a one-ounce serving of bread can have 95-210 mg of sodium while the same size serving of pretzels can have 290 to 560 mg of sodium.

The average American, according to the American Heart Association (AHA), consumes six to 18 grams of salt daily. However, the 2005 Dietary Guidelines for Americans established by the United States Dietary Association (USDA) recommends restricting daily sodium (salt) intake to 2300 milligrams (2.3 grams) or less – no more than about a teaspoon of table salt. This amount is more than half the amount typically consumed by Americans.

Because a small amount of sodium is vital for maintaining healthy body function, it is possible to have too little salt (sodium chloride). Symptoms of sodium deficiency include weakness, cramping, headache and (in severe cases) shock. However, this condition is rarely experienced by anyone other than athletes who have been sweating profusely for long periods of time, or people who regularly use diuretics or laxatives.