Introduction

Just how low salt should a low-salt diet be? Because salt reduction is often the first approach used to control high blood pressure, this was one of several questions posed by researchers from the Dietary Approaches to Stop Hypertension (DASH) study. The researchers compared the DASH diet with a typical Western diet at three different sodium levels, and the findings were published in a recent New England Journal of Medicine.

Study results

More than 400 men and women with blood pressures ranging from normal (120/80 mm Hg) to stage 1 hypertension (140-159/90-95 mm Hg), consumed either a typical Western diet or the DASH diet, which is rich in fruits, vegetables, low-fat dairy foods, whole grains, poultry, fish, and nuts, and includes only small amounts of red meat and sweets. The participants ate their assigned diet for 30 consecutive days at each of three sodium levels: high (3500 milligrams, the average American daily intake), medium (2300 mg, the upper end recommended), or low (1200 mg). They had their blood pressure monitored throughout the study.

Each level of sodium reduction lowered blood pressure in both the DASH and the Western diet groups. Volunteers eating the DASH diet had significantly lower blood pressure at all sodium levels than their counterparts assigned the Western diet. Of all the various dietary combinations, the DASH diet in conjunction with the lowest salt level provided the greatest reduction in blood pressures, equivalent to drug therapy provided to volunteers with hypertension. And the researchers note that both strategies--the DASH diet and lower sodium levels--reduced blood pressure in volunteers whether or not they had hypertension.

Hold the salt

Based on the results of this study, it appears that a recommendation to reduce sodium and eat meals patterned after the DASH diet is prudent advice for people with high blood pressure--and maybe even to those with normal blood pressure. The necessity of a generalized sodium restriction has been debated over the years because some scientists think that only a small percentage of the population is "salt sensitive", making a salt restriction unnecessary for the majority of Americans. This study provides new evidence that sodium restriction may affect blood pressure in the general population, and may provoke further discussion about the benefits of making public health recommendations reflecting these findings.

It's interesting to note that the current U.S. guideline for maximum sodium intake is 2300 mg per day and that blood pressure reductions were seen at this level. But this study shows that even greater reductions can be achieved at sodium levels of 1200 mg. However, processed and packaged foods are such a significant source of sodium, the authors admit that getting to a level this low would be difficult without considerable changes in eating habits.

Even at the 2300 mg level, though, the news is good.

Eighty percent of Americans over age 50 have blood pressure at least as high as the volunteers in DASH study. And even though they may experience no symptoms, increased blood pressure increases their risk of heart disease and stroke. For those folks, this study offers good news. They can lower their blood pressure with a healthful diet of fruits, vegetables, whole grains, legumes, low-fat dairy products, fish, poultry, minimal red meat and sweets... and by holding the salt.

Source

Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet.
FM. Sacks, LP. Svetkey, WM. Vollmer, New England Journal of Medicine., 2001, vol. 334, pp. 3--10

Links

• How to eat if you have high blood pressure
• Limit Sodium To Lower Blood Pressure
• Mediterranean Diet, Traditional Risk Factors, and the Rate of Cardiovascular Complications after Myocardial Infarction: Final Report of the Lyon Diet Heart Study.
• To quickly access additional accurate information on this and other nutrition-related topics, visit Tufts University's Nutrition Navigator http://www.navigator.tufts.edu