TABLE 3.

Results from the RCTs examining the hypotensive effect of the sodium-to-potassium (Na:K) ratio¹

First author, year, country (ref)	Population	Na+K vs. Na and/or K only examined?	Findings	Is the Na:K ratio more strongly associated with a hypotensive effect than Na and/or K alone?
Sacks, 2001, U.S. (DASH) (8)	Hypertensive + prehypertensive	Yes	“The DASH diet, as compared with the control diet, resulted in a significantly lower systolic blood pressure at every sodium level and in a significantly lower diastolic blood pressure at the high and intermediate sodium levels.… It had a larger effect on both systolic and diastolic blood pressure at high sodium levels than it did at low ones (P < 0.001 for the interaction).”	Yes
			“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 [prehypertension], and 11.5 mm Hg lower in participants with hypertension.”
			“…the combined effects on blood pressure of a low sodium intake and the DASH diet were greater than the effects of either intervention alone and were substantial…. We found that the reduction of dietary sodium significantly lowered the blood pressure of persons without hypertension who were eating a diet that is typical in the United States. These results should settle the controversy over whether the reduction of sodium has a worthwhile effect on blood pressure in persons without hypertension [prehypertensive status].”
Singh, 1993, India (38)	Hypertensive	No	“After 4 weeks of follow-up on an increased consumption of dietary potassium and low sodium/potassium ratio, group A [intervention] patients were associated with 7.5/8.5 mm Hg net decrease in mean systolic and diastolic pressures compared with group B [comparator]…. It is possible that an increased consumption of guava fruit can cause a substantial reduction in BPs and blood lipids with a lack of decrease in HDL-cholesterol due to its higher potassium and soluble fiber content, respectively.”	Not applicable
Langford, 1991, U.S. (39)	Hypertensive	No	“Assignment to the sodium restriction/increased potassium diet group did not substantially affect blood pressure.”	Not applicable
Bompiani, 1988, Italy (40)	Hypertensive	No	“During the modest sodium (100 mmol/d)/high potassium (130 mmol/d) diet the blood pressure was significantly reduced (−17/−6 mm Hg) when compared to the normal diet (160 mmol Na/day and 80 mmol K/ day).”	Not applicable
Nowson, 1988, Australia (41)	Hypertensive	Yes	“In each diet group the most significant dietary alteration was the reduction in the dietary sodium/potassium ratio [lowest in the low Na/high K group], and this was confirmed by the reduction in the urinary sodium/potassium ratio. The significance of this reduction is supported by the finding that the best predictor for reduction in diastolic response was the change in urinary sodium/potassium ratio.”	Yes
Suppa, 1988, Italy (42)	Hypertensive	Yes	“Our study... shows that in patients treated with a β-blocker, a slight potassium load (∼20 mmol daily) attainable by using a dietary salt at table, may produce a slight antihypertensive response, although this is largely limited to systolic BP.”	Yes
Grobbee, 1987, The Netherlands (43)	Hypertensive	Yes	“In conclusion, our observations suggest that moderate restriction of dietary sodium intake has little effect on blood pressure in young subjects with mildly elevated blood pressure levels, but the combination of moderate sodium restriction with high potassium intake may have an antihypertensive effect.”	Yes
			“Reducing the dietary sodium:potassium ratio may therefore be useful in the management of early primary hypertension.”
			“We found no significant change in plasma renin and catecholamines, nor was the change in blood pressure related to a change in these hormones.”
Valori, 1987, Italy (44)	Hypertensive	Yes	"The slight blood pressure decline over time when moderate Na restriction, or moderate Na restriction + low Na-high K salt, was added to the previous therapy should be viewed as an uncontrolled finding, not proving the antihypertensive efficacy of the dietary regimens tested.... no significant differences were found between moderate sodium restriction and moderate sodium restriction combined with the low Na-high K salt in their effects on blood pressure, either in patients on chlorthalidone or in patients on slow-release metoprolol.”	No
Arzilli, 1986, Italy (45)	Hypertensive	Yes	“In conclusion, our data show that a reduction in sodium intake from about 100 to 50 mmol/day, linked to a small (20 mmol/day) potassium supplementation, further and significantly decreases blood pressure in essential hypertensives, whose blood pressure is already reduced but not normalized by a relatively low sodium diet and/or hospitalization.”	Yes
Smith, 1985, U.K. (46)	Hypertensive	Yes	“Our findings showed that in patients with mild to moderate essential hypertension who were already moderately restricting their sodium intake to around 70 mmol/day doubling potassium intake as a chloride salt (64 mmol potassium chloride a day) did not cause any further significant fall in blood pressure.”	No
			“The lack of effect of potassium chloride on blood pressure when sodium intake is restricted could be due to potassium chloride having either less of a natriuretic effect or less effect on renin secretion.”
Fujita, 1984, Japan (47)	Hypertensive	Yes	“The results suggest that KCl may prevent a rise in blood pressure with NaCl loads in hypertensive patients by attenuating the increase in cardiac output, mainly as a result of the natriuresis.”	Yes
			”...KCl-induced natriuresis with the resultant decrease in body Na content may change the pressor responses to angiotensin II and catecholamines, which, in turn, promote the reduction of blood pressure.”
Richards, 1984, New Zealand (48)	Hypertensive	No	“The results show that moderate restriction of sodium intake or supplementation of dietary potassium has variable effects on arterial pressure in individuals with mild essential hypertension, and that overall the blood-pressure changes induced are very small. Responsiveness of the renin-angiotensin system may limit the fall in blood-pressure induced by sodium restriction.”	Not applicable
Skrabal, 1984, Austria (49)	Hypertensive	Yes	“It is concluded that sodium restriction to 80 mmol/day is effective in lowering systolic blood pressure but that a combined low-sodium/high-potassium diet does not further improve blood pressure control if the usual potassium intake is at least 80 mmol/day.”	No
Parfrey, 1981, U.K. (both hypertensive and normotensive populations included) (50)	Hypertensive	Yes	“The BP of mildly hypertensive patients responds to moderate alterations in the dietary intake of sodium and potassium continued for up to 12 wk and, in contrast to normotensive subjects, a high K/low Na intake significantly lowers BP. The mechanism of this depressor response remains unknown but there is no clear evidence that it is mainly dependent on a difference in the responses of the sympathetic or of the renin-angiotensin-aldosterone systems to the changes in electrolyte intake.”	Yes
			“Although PRA was lower in both groups during the high Na, and higher during the high K/low Na diet, none of the changes was significant within or between groups.”
Zoccali, 1985, Scotland (53)	Normotensive	No	“Although mean systolic pressure after potassium treatment was 4 mm Hg lower in the lying position and 6–8 mm Hg lower in the standing position than after the 2 control measurements (Days 5 and 15 [normal Na/K and unrestricted diets]), these differences were not significant. There were no significant differences in diastolic pressure between the 3 phases of the study.”	Not applicable
			“Plasma concentrations of renin and angiotensin II showed no significant changes after potassium treatment but there was the expected increase in plasma concentrations of renin and angiotensin II on standing (P < 0.001).”
Skrabal, 1981, Austria (52)	Normotensive	Yes	“The results of this study suggest that moderate salt restriction combined with a high potassium intake helps to prevent hypertension.…"	Yes
			“Of the many feed-back loops regulating blood pressure, at least 4 are influenced beneficially by moderate salt restriction and high potassium intake: (1) the renin-angiotensin system and (2) the aldosterone system which are brought back into their regulatory range where they can help to control sodium balance; (3) the sympathetic nervous system... and (4) the baroreceptor reflex which becomes more sensitive.”
Burstyn, 1980, U.K. (51)	Normotensive	Yes	“The relatively small reductions in sodium intake and increases in potassium intake that might be achieved through propaganda and changes in food processing are unlikely to lower mean blood pressure in Western societies. Such maneuvers may be useful to people who are genetically susceptible to salt-induced hypertension or whose salt intake is unusually high.”	No
			“A weak negative correlation was found between the sodium:potassium ratio and systolic pressure [among all patients combined].”

¹BP, blood pressure; DASH, Dietary Approaches to Stop Hypertension; PRA, plasma renin activity; RCT, randomized controlled trial; ref, reference.