Low-Fat, Low-Salt Diet
Cuts Blood Pressure
Excerpt By Merritt McKinney, Reuters Health

(Reuters Health) - A low-fat diet full of fruits and vegetables but little salt can lead to a significant drop in blood pressure--even in people with normal blood pressure--study findings show.

``This new study underscores the blood pressure-lowering effects of a reduced intake of salt and other forms of dietary sodium,'' said Dr. Claude Lenfant, director of the National Heart, Lung and Blood Institute in Bethesda, Maryland, which supported the study.

``Now we can say that cutting back on dietary sodium will benefit Americans generally and not just those with high blood pressure,'' Lenfant said in a statement.

Previous research on the link between sodium and blood pressure has provided mixed results in different groups of people, he noted.

But the findings do not mean that cutting salt intake will become the top priority of doctors who treat high blood pressure, also known as hypertension, according to a Texas physician.

``It is a good idea to limit salt intake if possible, because it might lower blood pressure,'' Dr. Cynthia Mulrow, of the University of Texas Health Science Center in San Antonio, told Reuters Health.

And despite some claims that a low-salt diet can have harmful long-term consequences, cutting back on salt is ''unlikely'' to be harmful, Mulrow pointed out.

However, despite the laudable goal of reducing salt consumption, Mulrow said, using the salt shaker less at home is not enough to make a serious reduction in salt intake.

``It is very difficult to limit salt intake to very low levels because processed foods, take-out foods and restaurant-prepared foods typically contain large amounts of salt,'' she explained.

In an editorial published with the new findings, Mulrow also points out that although a very-low-salt diet can lower blood pressure, few studies have examined whether the diet reduces complications of blood pressure such as heart attack and stroke.

In contrast, the benefits of blood pressure medications are well proven, she notes in the December 18th issue of the Annals of Internal Medicine.

In the same issue, Dr. William M. Vollmer, of the Center for Health Research in Portland, Oregon, and colleagues report the results of a study of 412 people who were randomly assigned to a typical US diet or a low-fat diet called DASH (Dietary Approaches to Stop Hypertension). The DASH diet focuses on fruit, vegetables, low-fat dairy foods, whole grains, poultry, fish and nuts.

Researchers also varied the participants' sodium intake, with each group consuming 3.5 grams, 2.3 grams and 1.2 grams per day for a month at a time during the 3-month study. Normal daily salt intake is considered to be 1.6 to 3 teaspoons of salt, which contains 3.1 to 6.0 grams of sodium.

At the start of the study, participants' systolic blood pressure--the upper number in a reading--ranged from 120 to 160 millimeters of mercury (mm Hg) and their diastolic pressure--the lower number--ranged from 80 to 95 mm Hg.

Blood pressure of 140/90 mm Hg or above is considered high--even if only one number is elevated. A reading from 130/85 to 139/89 is considered ``high normal.''

Both the DASH diet and salt reduction lowered blood pressure, but the drop was largest when the two approaches were combined, Vollmer and his colleagues report.

Cutting back on salt lowered blood pressure in many groups, including men as well as women, blacks and whites, the young and old, and people with normal or high blood pressure.

Given the well-established link between high blood pressure and an increased risk of cardiovascular disease, Vollmer's team concludes that the DASH diet in combination with low sodium intake ``should be broadly recommended'' for preventing and treating high blood pressure.

Although Mulrow expressed doubt that most people can stick to such a diet, she said many people may benefit from this advice: ``Eat fresh fruits and vegetables, don't add salt during food preparation or at the table, and avoid preprocessed prepared foods.''

Although some experts believe that medications should be the primary focus in lowering blood pressure, in another report in the same issue, researchers conclude that when it comes to cardiovascular benefits, not all of these drugs are created equal.

In the report, Dr. Curt D. Furberg, from Wake University School of Medicine in Winston-Salem, North Carolina, and colleagues challenge the idea that the main issue is to lower blood pressure by any means.

``We are starting to realize that it matters how blood pressure is lowered,'' he said in an interview.

Furberg and his colleagues cite the drug doxazosin as an example of a drug that can lower blood pressure but may not provide important cardiovascular benefits, such as reducing the risk of heart failure or stroke.

In fact, in an ongoing study comparing doxazosin with several other blood-pressure medications, researchers stopped the doxazosin arm of the study early when it became clear that people taking the drug had a 25% increased risk of cardiovascular disease.

According to Furberg, there are more than 100 blood-pressure drugs on the market. ``Doctors don't know which drugs to use,'' he said.

To help doctors make appropriate decisions when treating high blood pressure, Furberg said that there is a need for studies that compare drugs against diuretics. These drugs, Furberg explained, are the standard therapy for high blood pressure. Diuretics, which are available in generic form, are very cheap and have the most proven benefits, he said.

Another report in the journal concludes that patients who have type 2 diabetes in addition to high blood pressure need aggressive therapy.

``The rapidly increasing number of diabetics resulting from the current epidemic of obesity must have their hypertension effectively treated,'' Dr. Norman M. Kaplan, from the University of Texas Southwestern Medical Center at Dallas, told Reuters Health.

He noted that about 80% of all people with type 2 diabetes also have high blood pressure. Without proper control, Kaplan explained, high blood pressure in diabetics can accelerate cardiovascular complications, including heart attack and stroke, as well diabetic kidney failure, which is the leading cause of kidney failure.

In his report, Kaplan recommends keeping blood pressure below 130/80 mm Hg in people with type 2 diabetes. To achieve this goal, he advises using more than one drug. All patients should take a diuretic and an ACE inhibitor, if possible, according to Kaplan.

Lifestyle changes, such as weight loss, exercise and moderate consumption of sodium, protein and alcohol deserve attention as well, Kaplan notes.

SOURCE: Annals of Internal Medicine 2001;135:1019-1028, 1074-1086.

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