We've all known for some time that people with hypertension can lower their blood pressure by reducing the sodium in their diets. What we didn't know was whether, by consuming less salt (sodium chloride, the main form of sodium in the diet), these folks would also lower their risk of heart attacks.
An article published in the British Medical Journal now provides encouraging evidence for the long-term benefits of a sodium-restricted diet.
The study examined the heart health of people who had participated 10-15 years ago in either of two trials investigating how sodium intake affects blood pressure. Subjects in both trials were between the ages of 30 and 54 and had pre-hypertension, defined as a diastolic pressure between 80 and 89 mm Hg and a systolic pressure less than 140 mm Hg.
During the trials, their salt intake was reduced by 25 percent to 35 percent. One trial randomly assigned 744 subjects to either a lower-sodium diet or their usual diet for 18 months. The second trial randomized 1,191 subjects to a regular diet or a lower-sodium diet for a three- to four-year period.
Now, 10 to 15 years after the end of those trials, the researchers report that the study participants who had been in the sodium-restricted groups have had a 30 percent smaller number of heart attacks and strokes, angioplasty, and coronary artery bypass.
How could a relatively short period of salt restriction 10-15 years ago produce such long-term benefits even today? One explanation is that the study participants who were in the low-sodium groups were significantly more likely than those from the usual-care groups to continue using low-sodium products, read food labels for sodium content, and have a preference for low-sodium or unsalted foods.
The American Heart Association recommends consuming no more than 2,300 mg of sodium a day, an even greater limitation of dietary sodium than the 25 percent to 35 percent reductions used in the two trials. Many people require help from a dietitian to achieve this more restrictive goal, but even greater benefits might be anticipated from adhering to such lower sodium intakes.
It is likely that, had they participated in such studies of a reduced-sodium diet, people with full-blown high blood pressure would also have had fewer heart attacks and strokes. What isn't as clear is whether sodium restriction will either lower blood pressure or decrease the number of heart attacks and strokes in people who have neither hypertension nor prehypertension.
