By: Thomas Pickering, MD, DPhil, FRCP, Director of Integrative and Behavioral Cardiology Program
of the Cardiovascular Institute at Mount Sinai School of Medicine, New York.

Most trials of the effects of salt restriction and weight loss on blood pressure have been conducted in middle-aged people, although there is some evidence that older people may be more sensitive to the effects of salt on blood pressure than younger ones.

The largest study of non-drug treatment of blood pressure in older people (over the age of 60 years) is called TONE (Trail of Nonpharmacologic Interventions in the Elderly). It involved 875 men and women with mild hypertension controlled with a single blood pressure-lowering medication and a blood pressure of 145/85 mm Hg or lower. Participants who were overweight were randomly allocated to one of four treatment groups: salt restriction, weight loss, both, or neither (referred to as usual care). Those who were not overweight were randomized to salt restriction or usual care. Nutritionists and exercise counselors coordinated the treatment on an individual basis and with small groups of participants. The goal for salt restriction was a 24-hour sodium intake of 1800 milligrams (or 80 mmol) or less, which was evaluated by measuring the amount of sodium in a 24-hour urine collection. For the overweight participants, the goal was a weight loss of 10 pounds (4.5 kilograms). Another goal was to withdraw the blood pressure lowering medication: this was done if the blood pressure remained below 150/90 mm Hg over three visits to the clinic. The study lasted two and a half years.

The average decrease of salt intake was 900 milligrams, and the average weight lost was four pounds, which was approximately half the desired amount in both cases.

Approximately 30% more participants were able to stay off blood pressure-lowering medications at the end of the study if they were in the intervention group as opposed to the usual care group. Thirty-eight percent of participants who restricted their salt intake remained drug-free in comparison to 24% of the participants in the usual care group. For those who lost weight and restricted their salt, the results were even better: 44% could remain off drugs, as compared to 16% in the usual care group.

Doctor's comments

This is the first study to show that dietary changes can result in a substantial reduction in the need to take blood pressure-lowering medications in older people. The size of the changes needed to do this was relatively modest: a weight loss of four pounds in people who were overweight and a reduction of sodium intake of 900 milligrams. The average sodium intake was about 3,500 milligrams at the start of the study, which means that the achieved sodium intake was about 2,600, which is still above the 2,400 milligrams recommended by the FDA on food labels. One reason why these results are more impressive than the results of other comparable studies may be that the subjects in this study were all over the age of 60, whereas previous similar studies have included younger people. There is evidence that older people show bigger blood pressure changes in response to changes in salt intake than younger people.

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