Substitution of Smart Salt for Regular Salt in processed foods was a feasible measure that enabled the volunteers to achieve the recommended salt intake level of 5-6 grams per day. Previous studies have reported that the daily NaCl reduction should be at least 3.1 g to achieve a reduction of 4 to 5 mmHg in SBP and 2 to 3 mmHg in DBP in hypertensive subjects [13
]. In this study, a reduction of only 2.0 grams (measured by dU-Na) to 3.2 grams (measured by product diaries) resulted in a marked decrease of mean SBP (-7.5 mmHg) in the Smart Salt group in contrast to a slight increase of mean SBP (+3.8 mmHg) in the control group.
At baseline, daily sodium urinary excretion and dietary NaCl intake were at typical (or slightly lower) levels consumed in western populations [29
] The food diaries indicated that those in the Smart Salt group had their daily intake of sodium (as NaCl) reduced by 3.5 g compared to the Regular salt group. Also the difference in urinary sodium excretion between the groups at the end of intervention indicated a 3.3 g difference in mean sodium intake.
The consumption of Smart Salt mineral salt produced a stronger effect on BP than could be expected based on observed sodium excretion and previous pure sodium restriction studies [8
]. The results reported in this paper indirectly suggest that potassium and magnesium could potentiate the effect of sodium restriction on reducing BP. This effect is in line with earlier clinical trials with mineral salts [16
An increase of urinary potassium excretion of 63 mmol/24 hour has been associated with a decrease in supine SBP of 5.9 mmHg and in DBP of 3.4 mmHg [31
]. According to Whelton et al. [17
], supplementation with 2 g potassium decreases blood pressure an average of 2 to 3 mmHg. In our study, the net change in potassium excretion was about 30 mmol/24 hours, predicting a 3 mmHg reduction in SBP. The sodium to potassium ratio seems to be more important in potentiating the effect on BP than individual mineral modifications [32
]. It has been postulated that the effect of potassium supplementation is reduced by half if simultaneous daily sodium intake is under 3.2 g (8 g NaCl) and can be increased by double if sodium intake is over 3.8 g (9.5 g NaCl). Interestingly our result indirectly indicates that potassium substitution could be useful even at the recommended 5-6 g NaCl intake.
The high efficacy of mineral salts used in lowering BP might also be partly explained by the increase in magnesium intake. Magnesium supplementation has little direct effect on BP, especially in hypertensive subjects [32
]. However magnesium may have an effect on BP through interactions with sodium and potassium [20
]. Magnesium concentration was exceptionally high in the tested mineral salt (2.3% of total weight).
It should noted that the novel mineral enrichment used in the processed foods was likely to enhance the good compliance to sodium restriction throughout the study in the Smart Salt group. The taste profile of test products was good and products could not be differentiated from each other. It can be assumed that similar sodium restriction could not be easily achieved by simple salt restriction advice only. The self-reported compliance with the use of test foods and salts was good and biochemical data support this view.
Importantly lifestyle, weight and possible medications remained stable during the intervention. Thus the results could be principally ascribed to the intervention with Smart Salt low-sodium, high-potassium, high-magnesium mineral salt. Since the sample size in this proof-of concept study was relatively small, results will need to be repeated and verified with a larger sample size.
Salt substitution in processed foods and table salt may have a large impact on cardiovascular health at population level. Recently published analysis demonstrated that reducing salt by 3 g per day is projected to reduce the annual number of new cases of CHD by 60 000 to 120 000 in USA alone [7
In conclusion, the use of Smart Salt in processed foods helped subjects to bring their sodium intake in line with the recommended levels of 2.3 g/day (5.75 g as NaCl) [5
]. Additionally, this study indicates that replacing regular salt with a mineral salt low in sodium, high in potassium and high in magnesium may be a feasible way to potentiate antihypertensive effect in subjects with mild hypertension.