Low-salt diet tames hypertension

[Guest guest]

Low-salt diet tames hypertension

http://www.ynhh.org/healthlink/cardiac/cardiac_7_00.html

 

Findings from the DASH-Sodium trial, presented at the annual meeting

of the American Society of Hypertension in May, show a low-salt diet

results in substantial reductions in blood pressure in people with

and without hypertension. Hypertension, or high blood pressure, is

defined as readings consistently higher than 140/90 millimeters (mm)

of mercury (Hg). For people with diabetes, the goal is to maintain

blood pressure readings of 130/85 mm Hg or lower.

 

The study, which is supported by the National Heart, Lung and Blood

Institute (NHLBI), a division of the National Institutes of Health,

demonstrates decreases in systolic blood pressure (the upper number

in the blood pressure ratio) by an average of 8.9 mm Hg and in

diastolic blood pressure by an average of 4.5 mm Hg.

 

The benefit is substantial when dietary sodium is reduced in those

who have not yet developed high blood pressure.

" The findings should answer the question of whether or not reducing

dietary sodium benefits those without hypertension, " said NHLBI Dr. Claude Lenfant. " Earlier studies had differed in their

designs, leading to uncertainty over how worthwhile it is to reduce

dietary sodium for those who have not yet developed high blood

pressure. This well-controlled study had a diverse group of

participants and its findings show that the benefit is substantial. "

The blood pressure reductions occurred in men and women and in

African Americans and others.

 

First DASH study

DASH stands for " Dietary Approaches to Stop Hypertension. " The DASH-

Sodium trial is a follow-up to an earlier study involving the

effects of whole dietary patterns rather than of individual

nutrients on blood pressure. The findings, which were published in

The New England Journal of Medicine in 1997, showed the DASH diet

quickly and significantly reduced blood pressure.

 

The DASH diet is low in fat and cholesterol and emphasizes fruits,

vegetables, grains and low-fat dairy products. The diet includes

poultry, fish and nuts, but limits red meat, sweets and sugary

beverages.

 

The blood pressure reductions in that study occurred without changes

in weight, alcohol consumption or salt intake. All study

participants consumed about 3,000 milligrams (mg) of salt each day,

which is slightly below the average American's salt consumption.

 

DASH-Sodium focuses on salt

The DASH-Sodium study was conducted to look at the relationships

between blood pressure and various intakes of dietary salt. DASH-

Sodium involved 412 participants, age 22 or older. About 57 percent

of the subjects were women and 57 percent were African Americans.

Systolic blood pressures ranged between 120 and 159 mm Hg, and

diastolic blood pressures ranged between 80 and 95 mm Hg. About 41

percent of the participants were considered hypertensive.

 

Subjects were randomly assigned to one of two dietary plans for 14

weeks: a " typical " American diet and the DASH diet. Each of the

plans was broken into three different sodium levels — 3,300, 2,400

(which is the current recommended level) and 1,500 mg per day.

 

Results showed reducing salt lowered blood pressure in both the

typical American diet and DASH diet followers. The lower the sodium

intake, the lower the blood pressure. The biggest drops were among

those who followed the DASH diet at the lowest salt level. This plan

resulted in benefits to all participants–those with and without

hypertension, men and women, African Americans and others.

 

Overall, the DASH diet combined with low sodium intake reduced

systolic blood pressure by an average of 8.9 mm Hg and diastolic

blood pressure by an average of 4.5 mm Hg. In those with

hypertension, the combination reduced systolic blood pressure by an

average of 11.5 mm Hg. In those without hypertension, the

combination reduced systolic blood pressure by an average of 7.1 mm

Hg.

 

The take-home message is to " avoid processed foods because they are

so high in sodium. "

Researchers recommendations

" The results show that those with hypertension should follow the

DASH eating plan at a reduced sodium intake to help lower their

blood pressure, " said Dr. Frank Sacks, chair of the study's steering

committee. DASH co-investigators Dr. William Vollmer and Dr. Eva

Obarzanek said the take-home message is to " avoid processed foods

because they are so high in sodium. "

 

When asked if they would be making any recommendations to the

government based on their results, Dr. Obarzanek stated, " The

findings suggest that the current recommendation of how much dietary

sodium Americans should consume (2,400 mg/d) may need to be lowered.

By reducing salt intake to 1,500 mg a day, all Americans, and

especially those at a high risk for hypertension, can decrease their

chance of developing high blood pressure as they age. "

 

 

 

 

Physician Referral Online

 

A free and confidential service

of Yale-New Haven Hospital.

 

Physician Referral Online

Using your own criteria, you can request information from a database

of 900 area physicians who have registered to participate.

 

Request an appointment

We would be happy to assist you in scheduling an appointment with a

member of the hospital's medical staff. Use the link above or call:

 

203-688-2000

or toll free

1-888-700-6543

to talk with a referral coordinator.

 

 

 

 

 

 

 

Yale-New Haven was recognized this year by U.S. News & World Report

for its programs in cardiology and cardiac surgery.

 

 

DASH diet and less salt lowers blood pressure

 

This second DASH study is very important, and it will, I believe,

temper what has been a very heated debate among physicians over

whether reducing salt in one's diet reduces blood pressure. It

presents very clear, statistically significant evidence that for

people with and without high blood pressure, for men and women and

people of different racial backgrounds, reducing dietary salt helps

lower blood pressure.

 

" For people with and without high blood pressure, for men and women

and people of different racial backgrounds, reducing dietary salt

helps lower blood pressure. "

The original DASH study was undertaken to test the observation that

vegetarians tend to have lower blood pressure than nonvegetarians.

Since vegetarians consume higher levels of fiber, more fruits and

vegetables and more minerals, such as magnesium and potassium,

researchers compared subjects who consumed a diet comparable to that

of vegetarians with those who ate a more typical American diet,

higher in saturated fat, lower in fiber and fruits and vegetables.

 

The most dramatic results were noted in hypertensive patients whose

systolic and diastolic blood pressure dropped by 11.4 mm Hg and 5.5

mm Hg, respectively. These are very significant drops, comparable to

results obtained by placing patients on medication to lower blood

pressure.

 

Nonhypertensives benefited as well with drops of systolic and

diastolic blood pressure of 3.5 mm Hg and 2.1 mm Hg, respectively.

It's important to note these beneficial results were seen even when

weight and alcohol and salt consumption remained the same.

 

New DASH study strengthens the case

The DASH data has now been extended to factor in the role of salt.

Subjects in this study, which included both hypertensive patients

and those with normal blood pressure levels, were randomly assigned

to follow the DASH diet or a more typical American diet. These two

groups were further divided into three categories:

 

those who ate 3.3 grams of salt a day, the amount in the average

American diet;

those who ate 2.4 grams per day, the current recommended level; and

those who ate 1.5 grams per day.

At each of the three levels of sodium intake, blood pressure was

lower for those on the DASH diet than for those on the control diet.

 

" Reducing salt intake lowers blood pressure in addition to the

benefits obtained by consuming the DASH diet alone. "

The highest benefit was observed among hypertensives and the elderly

who were assigned to the lowest salt category and who were in the

DASH diet group. Their systolic and diastolic blood pressure dropped

by 11.5 mm Hg and 7.1 mm Hg, respectively. Participants who ate the

more typical American diet but who were in the lowest salt category

also benefited. More than half of their blood pressure reduction

occurred when they reduced their salt intake from the intermediate

to the lower level. The results show us reducing salt intake lowers

blood pressure in addition to the benefits obtained by consuming the

DASH diet alone.

 

There are individual variations in response to reduced salt intake.

Recent research indicates individuals with the " AA " variation of the

angiotensinogen gene are more sensitive to salt and are more

responsive to nutritional strategies to reduce blood pressure than

those who do not carry this variation of the gene, but everyone does

benefit.

 

" If Americans were to reduce salt consumption to 1.5 grams a day,

the prevalence of heart disease and stroke would decrease by 20 and

35 percent, respectively. "

The DASH-Sodium researchers estimate that if Americans were to

reduce salt consumption to 1.5 grams a day, the prevalence of heart

disease and stroke would decrease by 20 and 35 percent,

respectively.

 

Additional evidence

If that's not enough evidence, researchers added to the growing body

of data linking nutritional approaches to the prevention of

hypertension and heart disease at a conference held earlier this

year by the American Heart Association.

 

Blood clotting and inflammation in obese patients who ate whole

grains was reduced by 30 percent.

After 19 years, patients in the very large NHANES-1 database who

consumed fruits and vegetables three to four times a day lowered

their risk of stroke by 48 percent.

The addition of 40 grams of soy protein to the daily diet reduced

systolic blood pressure by 3.01 mm Hg more than in patients on a

placebo diet.

Reductions in blood pressure were also reported with daily increases

of omega-3 and linolenic acids, found in such foods as mackerel,

olive oil, tofu and flax seed. For each two grams of additional

omega-3 or linolenic acid consumption, both systolic and diastolic

blood pressures were lowered by 1 mm Hg.

What do we recommend?

Based on this dramatic evidence, what do we suggest? Avoid processed

foods and foods very high in salt such as pickles, potato chips and

canned soups. If you are like many Americans who crave salty foods,

you may discover as did subjects in the DASH-Sodium study, that you

begin to lose your taste for salt just two days after beginning a

low-salt regimen.

 

Interestingly, the DASH diet is very similar to the Mediterranean

diet we discussed in a HealthLINK feature last year, which also has

been shown to reduce the risk of heart disease. There is ample

evidence that a diet rich in fruits and vegetables, high in grains

but low in total and saturated fats and salt, supplemented by omega-

3 and linolenic acids, could significantly reduce the high rates of

heart disease and stroke in the U.S.

 

 

---

-----------

 

Dr. Mukherjee is a partner with Cardiology Associates of New Haven,

40 Temple Street, New Haven, CT. He is an attending physician at

Yale-New Haven Hospital and an assistant clinical professor of

medicine and cardiology at the Yale School of Medicine.