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Diet and Nutrition

Potassium & sodium

08/03/1998

Question:

Why are potasium & sodium important as individual minerals & when used together? What are the most natural ways to get these minerals? How much would you need a day? Please state this in amounts of food I would have to ingest in a day eg. nos.of bananas. Thankyou A.C.

Answer:

A.C, Thank you for your question. I will first discuss sodium, then potassium, and then their interrelationships.

Sodium is a mineral in the diet that is found mostly in the form of sodium chloride (40% of salt is sodium, 60% is chloride). It is used to season and preserve food. In your body, about 50% of sodium is in extracellular fluids (between cells), and 40% is in skeletal tissue, and approximately 10% is within the cells. Almost all of the sodium that you eat is absorbed from the gut and carried in the blood to the kidneys where it is filtered out, and returned to the blood in amounts our bodies need for functions in the body. Functions: Sodium helps maintain fluid balance in the body, and maintains acid-base (pH) balance. It is also a component of pancreatic juice, bile, sweat and tears. It is associated with muscle contraction and nerve function and aids in the absorption of carbohydrates in the diet. Deficiencies of sodium are rare because almost all foods contain some sodium. Deficiencies may occur when there has been prolonged sweating, diarrhea, vomiting or other medical conditions such as adrenal cortical insufficiency. A deficiency of sodium may cause reduced growth, loss of appetite, loss of body weight due to excess water loss, or reduced milk production in lactating women. Other symptoms include muscle cramps, nausea, diarrhea and headache.

Needs: there is no RDA (recommended daily allowance) for sodium, but an estimated amount for adults is 500 mg (or 0.5gm)/day. Most Americans eat between 2-10 gm/day, which is more than enough. I would not worry about getting enough sodium in your diet on a daily basis. Most Americans eat more than they really need.

Sources: foods high in sodium include salt, processed meats (bologna, sausage, bacon), canned soups, snack foods (chips, pretzels, nuts), v-8 juice and other seasoned or processed foods. In order to find the sodium content of a food, look on the nutrition label (of packaged foods).

Potassium is another important mineral needed in the body that is found in several foods. The body contains approximately 5% potassium, and the majority (98%) is found in intracellular (inside the cell) fluid and lean body tissue. Like sodium, potassium absorption is very efficient in the body, most absorption occurs in the small intestine. The kidneys regulate potassium balance, and excessive potassium buildup may result from kidney damage or failure.

Functions of potassium are similar to those of sodium. It is needed to maintain proper fluid balance in the blood, pH balance and in the transfer of nutrients in and out of individual cells. Potassium relaxes muscle (opposite of sodium which helps in muscle contraction). Potassium is also necessary for secretion of insulin by the pancreas, enzyme reactions, carbohydrate metabolism and protein synthesis.

Deficiency of potassium is very serious, and is more likely to occur (in some individuals) than sodium deficiency. A potassium deficiency may be caused by excess sweating, vomiting, diarrhea, burns or diuretic medications that force the body to excrete water and sodium. A potassium deficiency may cause rapid or irregular heartbeats, muscle weakness, irritability, nausea, vomiting, diarrhea and swollen abdomen.

Sources: Several foods are high in potassium and include oranges, bananas, kiwis, tomatoes, greens, broccoli, dried beans, milk, canteloupe, dried fruit, and salt substitute.

Needs: There is no RDA for potassium, but an intake deemed safe is 2000 mg/day. In order to meet your potassium needs for the day, you should consume at least 2 servings of fresh fruit, 2 servings of vegetables per day. If you eat a variety of foods in your diet from all food groups of the Food Guide Pyramid (grains, fruits, vegetables, meat, dairy and fat), you should have adequate potassium in your diet.

Interrelationship: Sodium and potassium function together in an electrogenic system in the body called the sodium/potassium pump. This "pump" is used to transfer nutrients across cells, for muscle contraction and relaxation, and nerve action.

The body needs to keep these two minerals in balance because they work opposite of eachother. Sodium and potassium have a relationship with blood pressure as well. If the content of sodium in the blood is high, this may affect water balance and may raise blood pressure.

A low sodium diet is recommended to control blood pressure, as well as conditions where the body is "holding" too much fluid (such as congestive heart failure, pre-menstrual bloating or kidney disease). Some studies show that a high potassium diet may help control blood pressure by affecting this balance of sodium and potassium in the blood. In addition, diuretics are often prescribed for people with high blood pressure, which can affect blood potassium levels.

I hope this answered your questions about sodium and potassium. Good luck to you!

Sincerely, Lisa Cicciarello, MEd, RD, CNSD

VA Medical Center, Cincinnati, Ohio

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Response by:

Kathleen Rourke, PhD, RN, RD, CHES
Formerly, Associate Dean
College of Allied Health Sciences
University of Cincinnati