The American Heart Association recommends that in addition to a healthy, balanced diet, Americans up to the age of 70 should consume approximately 2.7 teaspoons a day of salt (or about 1,500 mg) per day. This number is equivalent to the amount of sodium found in an average American's salt shaker. The recommended limit for those over 70 is lower at 1.6 teaspoons (or 810 milligrams). Salt intake may also play a role in preventing heart disease and stroke.
The exact amount of salt needed in the diet depends on a person's age, sex, and level of physical activity. The amount required may be reduced if a person eats more fresh produce and fewer processed foods. Americans typically consume too much sodium when most of the salt is added at the table, often by using too much table salt (sodium chloride) or cooking with an abundance of salt-packed seasoning.
The American Heart Association recommends that people who are sensitive to salt limit daily intake to 2,300 milligrams (about 1 teaspoon) of sodium or less per day. People who are physically active and healthy should aim for no more than 1,500 milligrams (about 3/4 teaspoon) of sodium per day. Americans who eat more than the recommended amount of sodium are at greater risk for high blood pressure, a disease of the heart and blood vessels in which the pressure of blood against artery walls becomes abnormally high. Sodium is required for cell metabolism, nerve impulse transmission and muscle contraction, but too much can cause fluid retention (edema).
Sodium is also needed for nerve transmission, blood pressure regulation and intestinal absorption. It helps regulate the body's water balance by helping to dilute body fluids. Aldosterone, one of several hormones that help regulate sodium intake in individuals eating a normal diet, aids in this process by stimulating increased kidney secretion of sodium when needed. Aldosterone also helps regulate potassium excretion. In people who consume more salt than is needed, aldosterone stimulates water retention and sodium and potassium excretion, while in those eating a low-sodium diet, there is low aldosterone activity.
In both cases, the result may be an increased loss of potassium. Potassium depletion can adversely affect the function of nerve cells and muscles, including the heart muscle. Potassium depletion in young people can cause serious problems such as hypokalemic periodic paralysis (HYPP) or hypokalemic periodic paralysis type 2 (hypoPP). HYPP is characterized by paralysis of the legs, followed by neck and facial muscles, with attacks happening most often during sleep. HYPP poses no health problems. HypoPP causes muscle weakness and lack of coordination.
Aldosterone is therefore an important factor in understanding why restricting an individual's sodium intake to abnormally low levels can produce such serious health consequences. Without sufficient sodium, potassium excretion is not regulated at appropriate levels. Aldosterone plays a critical role in regulating potassium excretion when sodium intake falls below necessary levels. The body responds to this situation by suppressing aldosterone secretion and stimulating the excretion of sodium and water to restore the appropriate sodium balance (1).
The physiological functions of aldosterone are under constant hormonal control. In one study, the researchers compared the effects of three doses of a diuretic (an agent that increases excretion of water and sodium) on plasma potassium and urinary potassium loss in eight men over two weeks. They found that the lower level caused a greater rise in plasma potassium than did the higher dose (2).
Some expectant mothers are urged not to take any salt during pregnancy because it can cause an increased risk for preterm delivery. The American Heart Association recommends that women who are capable of becoming pregnant should consume no more than 1,500mg or 3/4 teaspoon (of table salt) per day. Their usual diet should contain no more than 1,500 mg of sodium per day.
The amount of salt needed in the diet depends on a person's age, sex, and level of physical activity. The National Institutes of Health (NIH) recommends that healthy adults consume no more than 2,300 mg or 1 teaspoon (of table salt) per day. The Institute of Medicine recommends that people who are physically active and healthy should aim for no more than 1,500 mg (or 3/4 teaspoon) per day.
Unlike food additives used as agents to modify flavor or appearance, salt is an essential nutrient that is necessary in life processes such as nerve impulse transmission and muscle contraction. Like potassium, calcium and magnesium, salt plays a role in maintaining the body's fluid balance. But there is a high degree of individual variation in the response of each person to sodium. For example, some people may need less salt than others.
In addition to the American Heart Association recommendations, many countries recommend lower dietary intakes of sodium. In Japan, for example, persons over the age of 65 should consume no more than 2 grams (or 1/4 teaspoon) of salt per day. Those over 60 should consume no more than 1 gram (or 3/8 teaspoon). People who have a low-sodium diet should reduce their intake to no more than 2 grams per day (1/4 teaspoon) (3).
The Food and Drug Administration (FDA) estimates that the American diet contains far more sodium than is necessary. The FDA states that the typical American diet contains about 3,400 mg (about 1 teaspoon) of sodium per day, or about twice as much as is recommended. They estimate that cutting back to 1,500 mg/day would prevent 865,000 cases of hypertension and save $6.5 billion in medical costs.
A study published in JAMA found that cutting salt intake by an average of 3 grams (1/8 teaspoon) a day would lead to a drop in blood pressure and fewer strokes (4).
The side effects of excess sodium consumption include the following:
• Edema: From excess salt and insufficient exercise, body fluids are lost in the urine. To compensate, cells retain water. The extra fluid results in edema and eventually blockage in small blood vessels.
• Heart Disease: Intense sodium intake may cause high blood pressure by widening existing blood vessel walls or increasing the size of blood vessels to accommodate it (1). High blood pressure is a risk factor for heart disease and strokes.
• "Wear and Tear": While it is not clear how much of an association there exists between high sodium intake and osteoarthritis, high sodium intake has been associated with low bone density, which can exacerbate joint pain (1).
• Inflammation: High sodium intake has been linked to high levels of C-reactive protein, an inflammatory marker linked to heart disease and stroke risk.
• Bone Density: In postmenopausal women, the excess of dietary sodium may increase the loss of calcium from bones, according to some studies (5).
The following sources of sodium should be avoided in excess:
• Processed foods: Most processed foods contain some amount of salt. Substances like monosodium glutamate are used as flavor enhancers in many prepared foods. Canned soups, canned vegetables and packaged meals are common culprits.
• Table salt: Table salt is a refined salt product that has been stripped of nutrients.
• Pickled foods: Pickles and pickled vegetables such as sauerkraut can contain extremely high amounts of sodium (1).
• Condiments and sauces: Some condiments like soy sauce and barbecue sauce contain sodium. Salt is also added to some ketchups, mustards and relishes.
• Soda: Soda is full of sodium, even in the diet varieties. A twelve-ounce serving can have up to 250 mg of the substance. It is also high in sugar, which may be more harmful to overall health (1).
• Alcohol: A beer can contain up to 300 mg of sodium in a twelve-ounce serving.
• Fast food: Fast foods, especially processed fast foods are high in salt. Most of these restaurants will add additional salt to their meals, but there is often no way to tell how much is added on the menu.
• Processed meats: Commonly eaten processed meats like sausage and bacon contain high amounts of sodium (1).
• Meat and poultry: Some kinds of meat and poultry contain large amounts of sodium. Meat preserved with salt is called corned beef or corned beef hash (1).
• Preserves and sauces: Many kinds of preserves and sauces are high in sodium, including soy sauce, teriyaki sauce, barbecue sauce and ketchup (1).
• Bread: Most breads contain some salt. The amount varies by brand.
• Dried fruit: Dried fruits like raisins, dried apricots and dried plums can contain high amounts of sodium (1).
• Snack foods: Some salty snack foods such as chips, crackers and pretzels can have high amounts of sodium in them (1).
• Canned vegetables: Most canned vegetables are preserved with salt water or brine. These include seeds like black olives (1).
