What role for sodium?

It is estimated that in the United States, 50% of people over age 60 have high blood pressure, a condition long associated with sodium intake. It is surprising, therefore, that relatively few studies have examined whether reducing salt intake (a common initial treatment) effectively controls blood pressure in this group. Researchers from the Trial of Non-pharmacologic Interventions in the Elderly (TONE) study addressed this question and published their findings in a recent issue of Archives of Internal Medicine.

The study comprised almost 700 people ages 60-80 whose high blood pressure was controlled to 145/80 mm Hg or less (approximately high-normal range) with the use of one medication. Each volunteer was assigned to one of four groups: weight loss and reduced sodium, reduced sodium only, weight loss only, or usual dietary habits. Only participants that were overweight, based on an estimate of their body fat, were eligible for either of the weight loss groups.

Volunteers assigned to either the weight loss or sodium reduction groups met regularly with a nutritionist. The two groups who ate a reduced sodium diet were taught how to limit their sodium intake to a goal level of 1840 mg daily (2300 mg is the upper limit of the current recommendation). After 3 months of instruction, participants in all groups were gradually tapered off their anti-hypertensive medication.

Volunteers continued to have their blood pressure monitored to ensure that it remained at an acceptable level. If a participant's blood pressure rose to unacceptable levels or a request was made by either the physician or the patient to resume medication, the anti-hypertensive was reinstated. For the next 2½ years, researchers recorded how long each volunteer remained medication-free.

Lower salt, lower blood pressure

Participants in the sodium-restricted groups decreased their intakes by an average of about 900 mg per day, which is the equivalent of less than 1/2 a teaspoon of salt. Within 3 months (while participants were still taking their anti-hypertensive medications) there was a significant reduction in blood pressure. And more than two years later, 43% of those in the reduced sodium group still had normal blood pressure without the use of medication.

Shake the salt habit

If it is possible to control blood pressure simply by cutting back on salt, then it's probably prudent to teach your taste buds to enjoy less salty foods. Salt is an acquired taste. But the salt shaker is not usually the source of our excessive salt consumption. More often than not, it's the salt added to processed and prepared foods.

To effectively cut back on sodium, read food labels and look for "no added salt" or "reduced sodium" versions of your favorite canned vegetables, soups, and cold cuts. Switching from a cup of regular canned chicken broth to a lower-sodium version saves about 900 mg sodium-the reduction achieved by the volunteers.

The role of sodium restriction in reducing hypertension remains controversial, and all individuals do not respond equally to small changes in sodium intake. However, this particular study indicates that the public health message to - "choose and prepare your foods with less salt" - should be taken to heart by older adults.

Source

Effects of reduced sodium intake on hypertension control in older individuals.
LJ. Appel, MA. Espeland, L. Easter,  et al., Archives of Internal Medicine, 2001, vol. 161, pp. 685--693

Links

• Limit sodium to lower blood pressure
• How low should you go?
• Tufts University's Nutrition Navigator