Salt is a Major Risk Factor

Low Renin Hypertention: Low-renin hypertension, representing roughly one quarter of all essential hypertension, is widely recognized by distinct physiological features, including salt-sensitivity, diuretic- responsiveness. Tends to run in families. Low-renin was defined rigorously by plasma renin activity < or =0.69 ng angiotensin I/L per second, drawn when subjects had achieved balance after 5 to 7 days on a 10 mmol sodium diet and had stood upright for at least 1 hour. Harvd. Hypertension 2002 Apr;39(4):914-8

AHA On Salt: The AHA Nutrition Committee announced that there is no evidence that "limiting NaCl consumption to 6 g per day poses any health risk (Circ 98 98:613-17. A reduction of 2 mm Hg diastolic results in 15% decr stroke risk and 6% decr CHD risk. Chimp studies show adding 5g/d to usual low salt high K diet incr BP dramatically. Two meta-analyses of 32 and 52 studies both found reducing salt reduces HBP. Two meta-analyses found adding K supplements of 60-120 Meq/day lowers BP. Low calcium intake (300-600mg/d) assoc with HBP but unclear any diff at higher levels. K and calcium help offset high salt intake esp in hypertensives. Calcium does not prevent preeclampsia. Magnesium supplementation not found of benefit.

Salt Very Important Cause of Death: The rise in average blood pressure with age seen in Western populations does not occur in isolated traditional nomadic communities. Several factors contribute to the higher blood pressure in the West. Salt is particularly important, however, because its effect on blood pressure is large, the dietary intake by Western populations is high and a large reduction in its intake is realistic. The size of the relationship between salt and blood pressure depends on age and, in trials, the duration of reduction of intake of salt. Results of many of the randomized trials have suggested that reduction of dietary salt exerts only a small effect on average blood pressure; this is because their subjects have been young (average age 26 years) and trials have been of short duration (average 2 weeks). Analysis of observational data concerning various communities indicated that a reduction in dietary intake of sodium of 100 mmol/24 h (3 g of salt, a realistic reduction) lowers systolic blood pressure in subjects aged 50-65 years by 10 mmHg on average. Much evidence corroborates this estimate, including data from the Intersalt study and a randomized controlled trial of reduction of intake of salt by older persons. This reduction in blood pressure would reduce age-specific stroke mortality by an estimated 22% and mortality from heart disease by 16%. Reducing the amount of salt added to manufactured foods is an important public-health target. J Cardiovasc Risk 2000 Feb;7(1):5-8

Salt Restriction & Weight Loss Work Trials of Hypertension Prevention, phase 1, in Baltimore, Md. At baseline (1987 to 1988), subjects were 30 to 54 years old and had a diastolic blood pressure (BP) of 80 to 89 mm Hg and systolic BP <160 mm Hg. They were randomly assigned to one of two 18-month lifestyle modification interventions aimed at either weight loss or dietary sodium reduction or to a usual care control group. At the posttrial follow-up (1994 to 1995), BP was measured by blinded observers who used a random-zero sphygmomanometer. Incident hypertension was defined as systolic BP > or =160 mm Hg and/or diastolic BP > or =90 mm Hg and/or treatment with antihypertensive medication during follow-up. Body weight and urinary sodium were not significantly different among the groups at the posttrial follow-up. After 7 years of follow-up, the incidence of hypertension was 18.9% in the weight loss group and 40.5% in its control group and 22.4% in the sodium reduction group and 32.9% in its control group. In logistic regression analysis adjusted for baseline age, gender, race, physical activity, alcohol consumption, education, body weight, systolic BP, and urinary sodium excretion, the odds of hypertension was reduced by 77% (odds ratio 0.23; 95% confidence interval 0.07 to 0.76; P=0.02) in the weight loss group and by 35% (odds ratio 0.65; 95% confidence interval 0.25 to 1.69; P=0.37) in the sodium reduction group compared with their control groups. Hypertension 2000 Feb;35(2):544-9

Salt Sensitive Die Young: 17 yr study of 708 found that salt sensitive twice as likely to die. Weinburger, Indiana Univ, 10/25/00 meetings of American Heart Association's Council for High Blood Pressure Research. Only 10% salt from shaker and 85% in processed foods. Also increases calcium loss and osteoporosis. DASH study found reduced sodium diet cut BP in almost everyone.

DASH-II Says Limit 1150 mg/day of Sodium for Everyone: Minimum requirement for sodium is 500 mg/d according to National Academy of Science although no reference to this statement. DASH-II in NEJM 2001 found the less the salt, the lower the BP even for those with normal BP. The current governmental recommendation of 2500 mg/day maximum or 100 mmol is too high; DASH used 1150mg or 50 mmol for its lowest sodium group. 1500 mg sodium = 4 g of salt; the US average intake is 3,500 mg of sodium. BP decreased 3.0/1.6 mmHg when a low salt diet was added to DASH diet of fruit, vegetables and low-fat dairy. All groups benefited.

Low Salt, High Fruits and Vegetables, Low-Fat Dairy Lower BP Dramatically: DASH-II: Randomized feeding study. 412 adults with untreated systolic 120-160, diastolic 80 to 95 mm Hg. Followed the DASH diet or a control (typical U.S.) diet for three consecutive 30-day feeding periods, during which sodium intake (50, 100, and 150 mmol/d at 2100 kcal) varied according to a randomly assigned sequence. Body weight was maintained. In all subgroups, the DASH diet and reduced sodium intake were each associated with significant decreases in blood pressure; these two factors combined produced the greatest reductions. Among nonhypertensive participants who received the control diet, lower (vs. higher) sodium intake decreased blood pressure by 7.0/3.8 mm Hg in those older than 45 years of age (P < 0.001) and by 3.7/1.5 mm Hg in those 45 years of age or younger (P < 0.05). Ann Intern Med 2001 Dec 18;135(12):1019-28; Reducing the sodium intake from the high to the intermediate level reduced the systolic blood pressure by 2.1 mm Hg (P<0.001) during the control diet and by 1.3 mm Hg (P=0.03) during the DASH diet. Reducing the sodium intake from the intermediate to the low level caused additional reductions of 4.6 mm Hg during the control diet (P<0.001) and 1.7 mm Hg during the DASH diet (P<0.01). The effects of sodium were observed in participants with and in those without hypertension, blacks and those of other races, and women and men. The DASH diet was associated with a significantly lower systolic blood pressure at each sodium level; and the difference was greater with high sodium levels than with low ones. As compared with the control diet with a high sodium level, the DASH diet with a low sodium level led to a mean systolic blood pressure that was 7.1 mm Hg lower in participants without hypertension, and 11.5 mm Hg lower in participants with hypertension. The reduction of sodium intake to levels below the current recommendation of 100 mmol per day and the DASH diet both lower blood pressure substantially, with greater effects in combination than singly. Long-term health benefits will depend on the ability of people to make long-lasting dietary changes and the increased availability of lower-sodium foods. Sacks, Harvard, N Engl J Med 2001 Jan 4;344(1):3-10

DASH Diet Groups Did Best: 810 HBP patients were divided into Advice-Only, Established, and Established Plus DASH groups. All received printed materials about blood pressure and lifestyle. The Advice-Only group received a 30-minute individual session with a nutritionist, which did not include counseling on how to make behavior changes. The Established group had 18 counseling sessions in 6 months–14 group meetings and 4 individual sessions. They kept track of their diet, including calorie and sodium consumption, and their physical activity. The Established Plus DASH group had the same intervention schedule, but also were taught to follow the DASH diet and to record their daily servings of fruits, vegetables, dairy products, and fat. Systolic BP decreased 11.1 mm/Hg in the DASH group, 10.5 mm/Hg for the Established, and 6.6 mm/Hg for Advice with smaller but similar diastolic decreases. Advice at 6 months. JAMA 4/23/03

63% Increased Cardiovascular Death in Overweight High in Salt: NHANES study found the 25% of subjects who were overweight more sensitive to salt. Also 89% increase in strokes for each 100 mmol sodium (about 2200 mg salt). JAMA 21/1/99 or 00

Thomas E. Radecki, M.D., J.D.

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