Glossary: Sodium

sodium

What is it?

This MINERAL catches so much flak few of us realize that without it we would die. In a sort of yin-yang relationship with POTASSIUM, it regulates fluid balance in our bodies by controlling the flow of liquids in and out of individual cells. Classified as an electrolyte, sodium is also integral to the sparking of nerve impulses, the metabolism of PROTEINS and CARBOHYDRATES, the maintenance of the body's acid/alkali balance. Major tasks, all. Yet conventional wisdom tells us to "hold the SALT" lest our blood pressure soar. Biomedical researchers believe that this happens mainly in sodium-sensitive persons, that healthy individuals with normal blood presssures (120/80) are unlikely to become hypertensive if they don't cut down on salt.

Still, those who have high blood pressure (and fifty million Americans do), even those with marginally high blood pressure (140/90), should curb their sodium intake. That means putting the salt shaker away (both at stove and table) and scrutinizing food labels for ADDITIVES containing sodium as well as for salt (sodium chloride). It also means choosing reduced- or low-sodium canned foods and passing on most cured meats and cheeses, all of which brim with sodium. Finally, it may mean using one of the many salt substitutes.

Although there are no RDAs for sodium, the Committee on Dietary Allowances of the National Academy of Sciences (NAS) has established the Estimated Minimum Requirement at 500 milligrams per day. Further, the NAS's Committee on Diet and Health, in its 1989 report, recommended limiting the daily intake of salt to 6 grams (2,400 milligrams sodium), including that in prepared foods. This number, however, has been set arbitrarily as there are no studies showing the optimal level of sodium consumption.Table salt is 39 percent sodium and 1 teaspoon of it contains about 2,000 milligrams sodium. Though instances are rare, it is possible to be deficient in sodium. The likeliest candidates? Marathoners, who lose a load of sodium as they sweat, and habitual users of laxatives and/or diuretics.

Does aging affect blood pressure?

Yes. Older people are at greater risk of developing hypertension because of their decreased efficiency in absorbing minerals through the gut and their decreased renal efficiency in maintaining electrolyte balance. But not all elderly need to restrict their sodium intake; in fact, some can develop dizziness and hypotension if they do not maintain adequate sodium chloride intake.

Hypertension: The Silent Facts

Optimal blood pressure with regard to cardiovascular risk is <120 millimeters of mercury (mm Hg) systolic blood pressure and <80 mm Hg diastolic blood pressure. High blood pressure is diagnosed at >140 mm Hg systolic and >90 mm Hg diastolic.
As many as 50 million Americans have elevated blood pressure or are taking anti-hypertensive medications, according to data derived from the National Health and Nutrition Examination Survey (NHANES) III.
Hypertension has been clearly shown to increase the risk of developing stroke, coronary heart disease, congestive heart failure and other life-threatening conditions.
Prevalence of hypertension increases with age, is greater for African-Americans than for Caucasians, and in both races is greater in persons with less education.
High blood pressure is more prevalent in males than females during young adulthood and early middle age; thereafter the reverse is true.
Blood pressure fluctuates on a daily basis; diagnosis of hypertension requires at least two elevated readings taken one to several weeks apart.

Are Some People Sodium Sensitive?

There are people, such as African-Americans, whose consumption of sodium chloride appears to increase their risk of hypertension. This salt sensitivity is partly due to genetics, but also to environmental factors such as overweight, alcohol consumption and physical inactivity. Unfortunately, there's no diagnostic test to determine who's salt- sensitive - therefore, public policies have been set to protect this portion of the population. For example, the U.S. Dietary Guidelines recommend "Use salt and sodium only in moderation." The Daily Reference Value (DRV) for sodium on the new food label is set at 2,400 mg. This latter number, however, has been set arbitrarily as there are no studies showing the optimal level of sodium consumption.

Essential

USEFORTABLES
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