Eating large amounts of salt does not raise blood pressure for most of us (1,2), but it will for a few people. A new study in the Journal of Hypertension shows that these people can be detected by finding increased amounts of protein in their urines (3).
Evidently those who develop high blood pressure when they take in extra salt have kidneys that permit protein, called albumin, to pass through them. The old theory was that when you take in extra salt, it causes your body to hold extra water, expands blood volume and raises blood pressure, but most studies shows that low-salt diets do not lower high blood pressure (4,5,6). If you have high blood pressure, you can ask your doctor to check the amount of protein in a 24-hour urine collection. You can avoid adding extra salt to your cooking and food, but you don’t need to seek out and eat only foods that are very low in salt. Severe salt restriction is not safe. People on low-salt diets have a much higher death rate (7), and severe salt restriction can raise blood pressure (8) and blood cholesterol (9),/ and even cause a heart attack (10). Salt deficiency causes your kidneys and adrenal glands to produce large amounts of the hormones, renin and aldosterone, which raise blood pressure (8).
On the other hand, low-fat diets, exercise, weight reduction and alcohol restriction lower high blood pressure significantly (11), and adding blood pressure medicines to this regimen lowers high blood pressure even more (13). The 40% chance of lowering blood pressure with the most popular drugs is much lower than the 60% success rate of going on a low-fat diet and losing weight (14,15), so changing your lifestyle is far more effective in reducing high blood pressure than just taking drugs (16). Most doctors will recommend salt restriction.
By Gabe Mirkin, M.D., for CBS Radio News
1) JAMA May 21, 1996.
2) Science 1982 (April); 216(2): 38-40.
3) M Nesovic, M Stojanovic, MM Nesovic, J Ciric, M Zarkovic. Microalbuminuria is associated with salt sensitivity in hypertensive patients. Journal of Human Hypertension 10: 9 (SEP1996): 573-576.
4) Silman AJ, Locke C, Mitchel P. Humpherson P. Evaluation of the effectiveness of a low- sodium diet in the treatment of mild to moderate hypertension. Lancet 1983 (May 28): 1179.
5) BR Davis, A Oberman, MD Blaufox, S Wassertheilsmoller, N Zimbaldi, K Kirchner, J Wylierosett, HG Langford. Lack of effectiveness of a low-sodium high-potassium diet in reducing antihypertensive medication requirements in overweight persons with mild hypertension. American Journal of Hypertension 1994 (Oct); 7(10 Part 1): 926-932. This study provides no support for the sole use of a low-sodium/ high-potassium diet as a practical therapeutic strategy in maintaining blood pressure control in the moderately obese.
6) JD Swales. Salt and blood pressure revisited. Journal of Human Hypertension 9: 6 (JUN 1995): 517-5214.
7) Hypertension 25: 6 (JUN 1995): 1144-1152.
8) Klin Wochenschrift 1990; 68: 664-668.
9) Klin Wochenschrift 1991 69 suppl): 51-57.
10) American Journal of Hypertension 7: 10 Part 1: OCT 1994: 886-893.
11) Wt and dietary fat more important. Hypertension 1991; 18 (suppl 1): 115-120.
13) Effect of weight loss on blood pressure and insulin resistance in normotensive and hypertensive obese individuals. American Journal of Hypertension 8: 11 (NOV 1995): 1067-1071.
14) Hypertension 1991; 18 (suppl 1): 115-120.
15) American Journal of Hypertension 8: 11 (NOV 1995): 1067-1071.
16) JAMA May 22, 1996; 28(9): 1590-1597.