HYPE ABOUT SALT AND HIGH BLOOD PRESSURE

H228

Gabe Mirkin, M.D.

If you have high blood pressure, go on the DASH diet, lose weight if overweight and take medication if necessary. There is no good evidence that salt restriction alone helps lower high blood pressure.

A report from the Leicester Royal Infirmary in England reviews controlled scientific studies done throughout the world and found that salt restriction trials show extremely small drop of 1 mm of mercury for both systolic and diastolic blood pressures (1a). Most of these studies are done under conditions so severe that they are impractical. Furthermore, many doctors prescribe a low salt diet to treat high blood pressure, but even with intense counseling and instruction, fewer than 20 percent of patients are able to do it (1b).

A diet rich in fruits and vegetables is far more effective in lowering high blood pressure than a low-salt diet (2,3,4). Reducing salt intake a little does not lower high blood pressure (5,6) and reducing salt intake a lot can raise blood pressure even higher. Severe salt restriction causes your adrenal glands to produce large amounts of a hormone called aldosterone and your kidneys to produce large amounts of another hormone called angiotensin that constrict blood vessels and raise blood pressure (2,8,9). People on low-salt diets have a much higher death rate (10), and severe salt restriction can raise blood pressure (11) and blood cholesterol (12), and even cause heart attacks (13).

Obese people are often sensitive to salt because being overweight prevents your body from responding adequately to insulin and raises insulin levels. Since insulin, itself, causes the body to retain salt, salt restriction raises blood levels of insulin which make a person hungry and fatter. Eating white flour and sugar makes your body much more sensitive to salt and restricting these food products decreases salt's ability to raise blood pressure (14). The 40 percent chance of lowering blood pressure with the most popular drugs is much lower than the 60 percent success rate of going on a low-fat, high-fiber diet and losing weight (15,16). Changing your lifestyle is far more effective in reducing high blood pressure than just taking drugs. If your doctor recommends salt restriction, follow the DASH diet which is naturally low in salt.

checked 5/10/07

1a) J Swales. Population advice on salt restriction: The social issues. American Journal of Hypertension, 2000, Vol 13, Iss 1, Part 1, pp 2-7.

1b) MH Korhonen, H Litmanen, R Rauramaa, SB Vaisanen, L Niskanen, MIJ Uusitupa. Adherence to the salt restriction diet among people with mildly elevated blood pressure. European Journal of Clinical Nutrition, 1999, Vol 53, Iss 11, pp 880-885.

2) Appel LJ et al. A clinical trial of the effects of dietary patterns on blood pressure. NEJM, 1997 (April 17);336:1117-1124.

3) Hypertension 1991;18 (suppl 1):115-120.

4) American Journal of Hypertension 8: 11 (NOV 1995):1067-1071.

5) JAMA, May 21, 1966.

6) JAMA, May 6, 1998.

7) JAMA, December 20, 1995.

8) JAMA, May 22/28\9. 1996.Pages 1590-1597.

9) Hypertension 25: 6 (JUN 1995):1144-1152.

10) Hypertension 25: 6 (JUN 1995):1144-1152.

11) Klin Wochenschrift 1990;68:664-668.

12) Klin Wochenschrift 1991 69 suppl):51-57.

13) American Journal of Hypertension 7: 10 Part 1:OCT 1994:886-893.

14) TA Kotchen, JM Kotchen. Dietary sodium and blood pressure: Interactions with other nutrients. American Journal of Clinical Nutrition 65: 2 Suppl.(FEB 1997):S708-S711.

15) Hypertension 1991;18 (suppl 1):115-120.

16) American Journal of Hypertension 8: 11 (NOV 1995):1067-1071.

Checked 7/8/07