Sodium is a metallic element whose symbol is Na. When combined with chloride, sodium forms table salt, or NaCl. Sodium ions are soluble in water, a property that allows sodium to exist as one of the predominant ions in your blood and body fluids. According to nutritionist Elson Haas, M.D., in his book "Staying Healthy with Nutrition," about 60 percent of your body's sodium is in the fluids around your cells, 10 percent resides within your cells and 30 percent is sequestered in your bones. Adding salt to your foods can contribute to high blood pressure.
Fluid Movement
In conjunction with potassium, sodium helps to control the movement of fluid into and out of your cells. Water moves toward areas where the concentration of sodium ions is the greatest. Your kidneys are designed to keep sodium in your body, so increasing your dietary intake of sodium increases your retention of water. This increases the total volume of fluid in your blood vessels, which tends to elevate your blood pressure. A 2011 study conducted by the Public Health Agency of Canada demonstrated that people who eat more salt are more likely to have high blood pressure.
Salt vs. Sodium
Dietary guidelines for healthy salt intake can be confusing. Table salt is not pure sodium. It is 60 percent chloride by weight. Therefore, 5 g of table salt -- about 1 tsp. -- only contains 2 g of sodium. Most dietary recommendations are written in terms of sodium consumption, rather than total salt intake. So, a guideline calling for a daily sodium intake of 1,500 mg translates to a salt intake of 3,750 mg, or around 3/4 tsp. of table salt.
Considerations
A February 2002 review in "The Journal of the American Medical Association" reported that your risk for developing hypertension, or high blood pressure, sometime during your lifetime is 90 percent. According to Haas, much of this risk stems from the fact that people in Western cultures consume 6 to 12 g of salt daily. Although some people are more "salt-sensitive" than others, your blood pressure rises in proportion to the amount of sodium you consume in excess of 1,500 mg daily.
Recommendation
In 2004, the Institute of Medicine established adequate intakes, or AIs, and tolerable upper intake levels, or ULs, for sodium in adults of different ages. AIs represent the amount needed for optimal health, while ULs represent a healthy dietary "ceiling" for the nutrient. These guidelines apply to healthy adults at an average level of exertion. Sodium losses due to excessive sweating will increase your daily salt requirements. The AIs for adults are: under 50 years of age, 1,500 mg daily; ages 50 to 70, 1,300 mg; over 70, 1,200 mg. The UL for all adults is 2,300 mg. Multiply each of these numbers by 2.5 to determine its equivalent in table salt.
References
- "Staying Healthy with Nutrition"; Elson M. Haas, M.D.; 2006
- "Chronic Diseases in Canada"; Dietary Sodium Intake Among Canadian Adults with and Without Hypertension; Y. Shi, et al.; March 2011
- "The Journal of the American Medical Association"; Residual Lifetime Risk for Developing Hypertension in Middle-Aged Women and Men; V.S. Ramachandran, et al.; February 2002
- Institute of Medicine; Dietary Reference Intakes: Water, Potassium, Sodium, Chloride, and Sulfate; February 2004
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