recently , there has been a hot debate over whether current salt intake is too high from a health perspective . it is estimated that globally 62% of cerebrovascular disease and 49% of ischaemic heart disease were attributable to elevated blood pressure . a technical report produced by who and the food and agriculture organization of the united nations recommended the consumption of less than 5 g of salt per day as a population nutrient intake goal . given the adverse impact of excessive salt consumption on health and particularly on blood pressure levels and cardiovascular diseases , the world health organiztion has urged member nations to take action to reduce population wide dietary salt intake to decrease the number of deaths from hypertension , cardiovascular disease and stroke ( who report 2006)1 ) . salt is an ionic compound composed of sodium chloride , which is 40% sodium and 60% chloride . the molar mass of salt is 58.443 g / mol , its melting point is 801(1,474 ) and its boiling point 1,465(2,669 ) . salt is readily soluble in water and dissolved in water it separates into na and cl ions . over the past century , sodium chloride has been the subject of intense scientific research related to blood pressure ( bp ) elevation and cardiovascular mortalities . however , recently some in the academic society and lay media dispute the benefits of salt restriction , pointing to inconsistent outcomes noted in some observational studies2,3 ) . for millions of years , human beings ate very small amounts of salt ( 0.1 - 0.5 g / day ) . among the food that humans ingest , meat has the highest salt content ( about 0.6 g of salt per pound ) . during the hunter - gathering period , the main food for human being was meat . so the intake of salt in paleolithic times was less than 1 g / day . in the mean times , population growth led to the introduction of agriculture , and during the first few thousand years after the advent of agriculture , the intake of meat declined and the intake of vegetables increased up to 90% . in the agricultural period , human beings consumed about the same amount of salt as did their hunter - gathering ancestors4 ) . people living in romania were boiling the salt - laden spring water to extract the salts . the harvest of salt from the surface of xiechi lake near yuncheng in shanxi , china , dates back to at least 6000 bc , making it one of the oldest verifiable saltworks5 ) . about 5,000 years ago , the chinese discovered that salt could be used to preserve food . salt then became of great economic importance as it was possible to preserve food during the winter and allowed the development of settled communities . with the increased use of salt , about 1,000 years ago , salt intake in the western world had risen to about 5 g / day6 ) . herodotus , an ancient greek historian , described salt trading routes that united the salt oases of the libyan desert back in the 5 century bc . in the early years of the roman empire , roads such as the via salaria were built for the transportation of salt from the salt pans of ostia to the capital7 ) . with the spread of civilization , salt became one of the world 's main trading commodities . the oppressive salt tax in france was one of the causes of the french revolution . in india , this tax gave rise to a civil disobedience campaign under mahatma ghandi against the british8 ) . salt is an essential electrolyte to life in human beings and is used universally in cooking , seasoning , and preserving manufactured food stuffs around the world . for several million years , human ancestors ate a diet that contained less than 1 g of salt per day . salt was the most taxed and traded commodity in the world , with intake reaching a peak around the 19 century9 ) . however , salt was no longer required as a food preservative with the invention of the refrigerator . salt intake had been declining , but with the recently large increase in the consumption of highly salted processed food , salt intake is increasing towards levels similar to those of the 19 century , and is approximately 9 - 12 g / day in most countries around the world10 ) . iodine is an important micronutrient for humans and iodized table salt has significantly reduced disorders of iodine deficiency . however , in naturally occurring foods such as meats , vegetables , and fruits , salt is present in small quantities . there is more salt in animal tissues such as meat , blood and milk , than there is in plant tissues11 ) . they do not eat salt with their food , but agriculturalists , feeding mainly on cereals and vegetables , need to supplement their diet with salt12 ) . recently many processed foods use large amounts of salt and over 75% of daily sodium intake comes from salt found in processed foods . sodium serves as an important nutrient in the body and helps nerves and muscles to function correctly . it is also involved in the auto - regulation of the water and fluid balance of the body . high dietary salt intake presents a major challenge to the kidneys to excrete large amounts of salt administered . one of the main organ systems vulnerable to the adverse effects of excessive sodium in the diet is the cardiovascular system . the earliest comment relating dietary salt intake to bp was by the chinese medical doctor in 2698 - 2598 bc(huang ti nei ching su wen ; the yellow emperor 's classic of internal medicine ) : " therefore if large amounts of salt are taken , the pulse will stiffen or harden"15 ) . the association between salt intake in the diet and bp was first suggested by ambard and beaujard in 190416 ) . salt intake was measured by estimating the salt content of the food and the urine each day . when the diet contained little salt , the patients went into negative sodium balance and blood pressure fell , even though the intake of protein was raised . conversely , when the diet was high in salt , less salt was excreted in the urine so that the patient was in positive sodium balance and the bp rose even when the protein intake was low . they had some success in reducing bp by restricting salt intake . in 1948 , kempner introduced rice diets for the treatment of hypertension . he treated 500 hypertensive patients with a diet containing 20 g of protein , little fat , and < 0.5 g salt . he showed that rice diets containing little salt improved bp , decreased heart size , reversed inverted t waves in the ekg , and ameliorated hypertensive retinopathy . however , a rice diet did not have widespread acceptability because of insipid and unpalatable features of food contents . the connection between high salt intake and elevated bp became widely recognized after kempner 's rice diet in 1948 and thus , high bp was lowered by a low salt diet and a renewed salt restriction strategy utilized in the treatment of hypertension17 ) . since then , many animal studies showed a causal relationship between dietary sodium and hypertension and in human studies , established that the average bp in the population is related to habitual salt intake13 ) . the available data in animal studies confirm the existing relationship between habitual salt intake and bp levels . a well - documented connection between hypertension and dietary salt intake has been demonstrated in various animals , especially in rats and chimpanzees . ball and meneely18 ) reported that in groups of young adult rats that were fed different amounts of salt in their diet ( 0.15 , 2.8 , 5.6 , 7.8 , or 9.8% ) with free access to distilled water , the average bp after 9 month increased proportionally to the amount of salt in their diet . a similar study had been performed in chimpanzees , which are genetically very close to humans , by denton et al.19 ) . chimpanzees normally consume a diet low in salt , but when their salt intake increased to ~15 g / day for 20 months , they developed hypertension . the rise in bp was gradual and it was still rising 18 months after they started the high salt diet . moreover , when the salt was reduced from the diet containing ~15 g salt / day to 0.5 g salt / day , blood pressure levels fell back to the original level after 6 months . in this study , we can see a progressive increase in bp with added salt and this was completely reversible when the added salt was stopped . studies on the effect of salt intake on bp in humans have been carried out extensively for the past several decades . after kempner 's rice diet in 1948 , other investigators showed the bp lowering effect of a low salt diet20 ) . however , it was a very difficult thing to reduce the salt intake below 1 g / day in the everyday food intakes in humans . regional differences in habitual salt intake and bp within a population have been studied in various areas of the world . around the newfoundland area , a survey of salt intake revealed that a county in the center of the island had a typical salt intake varying between 6.7 and 7.3 g / day . in contrast , the salt intake varied between 8.4 and 8.8 g / day in a relatively isolated coastal community21 ) . this difference in salt intake was accompanied by parallel changes in the incidence of hypertension . in individuals aged between 55 and 75 years , the incidence of hypertension in the inland community was 15% while it was 27% in the coastal community . similar evidence had been obtained among the solomon islanders22 ) . in those tribes , which lived away from the coast and had a salt intake below 2 g / day , only 1% of the population had a raised bp . in two tribes with salt intakes between 3 and 8 in one tribe , which lived on the coast and had a salt intake between 9 and 15 g / day , 8% of the population had a raised bp . studies of population groups that migrated from areas with lower salt intake to areas with higher salt intake have reported increases in bp . a carefully controlled study from kenya showed that the migrants who had higher mean urinary sodium / potassium ratio compared to the non - migrants had higher systolic bp23 ) . blood pressure in these migrants rose after a few months ( 6.9/6.2mmhg for systolic and diastolic ) , whereas it did not increase in a control group who did not migrate24 ) . another example of the effect of life - style changes including dietary sodium intake on bp is that of the yi people , an ethnic minority living in southwestern china . blood pressure rose very little with increasing age ( 0.13 and 0.23mmhg / year for systolic and diastolic , respectively ) in the yi farmers who lived in a remote mountainous environment and consumed a sodium - poor diet . in contrast , yi migrants and han people who lived in urban areas consumed a sodium - rich diet and experienced a much greater increase in bp with progressive aging ( 0.33 and 0.33mmhg / year for systolic and diastolic , respectively)25 ) . these findings suggest that changes in life - style , including higher intake of dietary sodium , contributed to higher bp among yi migrants . a large number of epidemiologic , evolutionary , and clinical studies have confirmed that salt intake is an important factor in elevating the bp in humans . the first double - blind controlled study of moderate salt restriction was performed in the early 1980 's by macgregor et al.26 ) . they recruited nineteen unselected patients with mild to moderate essential hypertension , whose average supine bp after two months ' observation and no treatment was 156/98mmhg . after 2 weeks of sodium restriction , patients were entered into an 8-week double - blind randomized crossover study of ' slow sodium ' ( ciba , 10mmol of sodium per tablet ) versus slow sodium placebo . the mean supine bp was 7.1mmhg ( 6.1% ) lower in the fourth week of slow sodium placebo than that in the fourth week of slow sodium ciba ( p<0.001 ) . urinary sodium excretion in the fourth week of slow sodium ciba was 1629mmol/24 hours and that in the fourth week of slow sodium placebo was 869mmol/24 hours ( p<0.001 ) . they suggested that moderate sodium restriction should become part of the management of essential hypertension . followed by this study , many large observational and epidemiological investigations conducted worldwide link between high salt intake and hypertension . intersalt study was one of the first large international epidemiologic studies on sodium intake and hypertension using a standardized method for measuring 24-hour urinary sodium . this study , which was a crosssectional assessment of 10,079 subjects aged 20 - 59 sampled from 52 centers around the world , attempted to relate sodium intake to bp from an epidemiological perspective . sodium excretion ranged from 0.2mmol/24 hours ( yanomamo indians , brazil ) to 242mmol/24 hour ( north china ) . in individual subjects ( within centers ) , salt intake was significantly related to bp . four centers found very low sodium excretion , low bp , and little or no upward slope of bp with age . across the other 48 centers sodium was significantly related to the slope of bp with age but not to median bp . the study demonstrated a significant positive relationship between salt intake and bp in individual subjects within centers . in an initial analysis of 48 of the 52 centers , however , after inclusion of the remaining 4 centers , in which the average sodium consumption was 0.2 - 50mmol / day , they found a significant association between salt intake and the increase in bp with age . furthermore , it also found that populations with low average daily salt intakes had low bp and very little or no increase in bp with age27 ) . intersalt study indicates that bp increases with age only if accompanied by increased salt intake . as part of the intersalt study , bp , urinary electrolytes , age , and body mass index were assessed in a sample of 195 yanomamo indians from the brazilian amazon28 ) . mean sodium excretion was 0.9mmol / day . systolic and diastolic bp were not higher at older than at younger ages in men . in women , in this tribe , there was a low average population bp , no hypertension and no positive slope of bp with age in a population with very low salt intake . salt institute criticized that in an initial analysis of 48 of the 52 centers , no significant association was noted between sodium intake and median bp . however , the intersalt 's investigators re - analyzed their data and showed that the highly significant within - population association between salt intake and bp across all 52 centers was virtually unchanged . lowering sodium intake by 100mmol was associated with a 3mmhg decrease in systolic bp29 ) . there are several studies on the effect of reducing the salt intake on bp on a community levels . forte et al.30 ) studied reducing the dietary salt intake on bp on a community in portugal , which is notorious for its high consumption of salt . the trial was performed in two communities within the same district , each with 800 inhabitants who had salt intakes of ~21 g / day and a 30% incidence of hypertension . in the intervention community the reduction in salt intake in one of the communities to ~12 g / day was associated with a highly significant difference in bp . by the end of the second year , there was a small rise in systolic bp in the control community and a significant fall in both systolic and diastolic bp in the low salt intake community , the difference between the two villages reached 13/6mmhg . the fall in bp involved the whole community , normotensives and hypertensive individuals alike , and the response did not differ between the young and the old or between men and women . those with the greatest fall in salt excretion tended significantly to be also those who showed the greatest fall in bp . the other long - term trial was carried out in tianjin in china as part of a community - based intervention program to reduce non - communicable diseases31 ) . this intervention was based on examinations of independent cross - sectional population samples in 1989 ( 1,719 persons ) and 1992 ( 2,304 persons ) in the intervention and matched reference areas . the mean reduction in salt intake was 1.3 g / day in men and 0.7 g / day in women in the intervention area from 1989 to 1992 . during the same period , the reduction was statistically significant in men ( p<0.001 ) and near significant in women ( p<0.05 ) . in the intervention area , the mean systolic bp decreased by 3mmhg for the total population and by 2mmhg for normotensive people . another long - term trial was performed in two belgian towns of 12,000 and 8,000 inhabitants , situated within 50 km of each other32 ) . the low - sodium intervention in one town was mainly directed at women and implemented through mass media techniques , while the control town was merely observed . cross - sectional random sampling at baseline and 5 years later was employed , the participation rate being similar ( 67% ) in the two towns . during the study a total of 2,211 subjects were examined . in adult women ( greater than or equal to 20 years ) in the intervention town the 24-hour urinary excretion of sodium(uvna ) decreased by 25mmol/24 h ( p<0.001 ) and this reduction differed ( p=0.01 ) from the concurrent trend in uvna in the control town ( + 8mmol/24 h ) . however , both systolic bp ( -7.5 versus -7.9mmhg ) and diastolic bp ( -2.3 versus -3.0mmhg ) declined to a similar extent in the women from the two towns . in adult men in the intervention town , decreases were observed in uvna ( -12mmol/24 h ) and in systolic bp ( -5.6mmhg ) and diastolic bp ( -2.4 mmhg ) , but these trends were not significantly different from the concurrent changes in the control town ( -14 mmol/24 h , -4.9 and + 0.2mmhg , respectively ) . no significant difference was observed in the evolution of mean systolic and diastolic pressures that declined to the same extent in the two towns during the trial . in women of the intervention town , 24-hour urinary salt excretion decreased by 1.5 g , whereas in the control town it rose by 0.5 g. this negative result may be explained by the small reduction in salt consumption that would be insufficient to observe a net effect on bp in the belgian environment . these results suggest that a reduction in salt consumption is difficult to achieve with mass media techniques and in women and in subjects aged 50 years or more , the intervention did achieve some success , but bp was not affected . there were many randomized clinical trials performed to test the effects of reducing salt intake on bp . cutler et al.33 ) analyzed previously published randomized clinical trials testing the effects of reducing sodium intake on bp . thirty - two trials with outcome data for 2,635 subjects were included . pooled bp differences between treated and control groups were highly significant for all trials combined . the effects on blood pressure by lowering sodium in hypertensive and normotensive subjects were -4.8/-2.5 and -1.9/-1.1mmhg ( systolic / diastolic ) , respectively . median differences in sodium excretion between sodium - reduction and control groups in these subgroups were -77 and -76mmol/24 h , respectively . weighted linear - regression analyses across the trials showed dose responses , which were more consistent for trials in normotensive subjects . these analyses yielded estimates , per 100mmol of sodium reduction , of -5.8/-2.5mmhg in hypertensive subjects and -2.3/-1.4mmhg in normotensive subjects , respectively . there is no evidence that sodium reduction as achieved in these trials presents any safety hazards . they concluded that the bp reduction with a substantial lowering of dietary sodium in the us population could reduce cardiovascular morbidity and mortality . however , in two other meta - analyses34,35 ) , it was claimed that salt reduction had very little effect on bp in individuals with normal bp and a reduction in population salt intake was not warranted . the meta - analysis by midgley et al.34 ) included 56 trials that had randomized allocation to control and dietary sodium intervention groups with outcome measures of both systolic and diastolic bp . the mean reduction in daily urinary sodium excretion was 95mmol / day ( 71 - 119mmol / day ) in 28 trials with 1,131 hypertensive subjects and 125mmol / day ( 95 - 156mmol / day ) in 28 trials with 2,374 normotensive subjects . the decrease in bp for a 100mmol / day reduction in daily sodium excretion was 3.7mmhg ( 2.35 - 5.05mmhg ) for systolic ( p<0.001 ) and 0.9mmhg ( -0.13 to 1.85mmhg ) for diastolic ( p=0.09 ) in the hypertensive subjects , and 1.0mmhg ( 0.51 -1.56mmhg ) for systolic ( p<0.001 ) and 0.1mmhg(-0.32 to 0.51mmhg ) for diastolic ( p=0.64 ) in the normotensive subjects . decreases in bp were larger in trials of older hypertensive individuals and small and non - significant in trials of normotensive individuals . they concluded that dietary sodium restriction for older hypertensive individuals might be considered , but the evidence in the normotensive population does not support current recommendations for universal dietary sodium restriction . another meta - analysis by graudal et al.35 ) included 58 trials of hypertensive and 56 trials of normotensive person to evaluate the effect of sodium restriction to blood pressure lowering . in 58 trials of hypertensive subjects , the effect of reduced sodium intake as measured by urinary sodium excretion ( mean , 118mmol/24 h ) on systolic bp was 3.9 mmhg ( p<0.001 ) and on diastolic bp was 1.9mmhg ( p<0.001 ) . in 56 trials of normotensive subjects , the effect of reduced sodium intake ( mean , 160mmol/24 h ) on systolic bp was 1.2mmhg ( p<0.001 ) and on diastolic bp was 0.26mmhg ( p=0.12 ) . they concluded that these results do not support a general recommendation to reduce sodium intake . however , these two meta - analyses were criticized by some authors because the data included was flawed . both meta - analysis included trials of very short duration with comparing the effects of acute salt loading to abrupt and severe salt restriction for only a few days . it is inappropriate to include the acute salt restriction trials in a meta - analysis where the implications of the findings are to apply them to public health recommendations for a long - term . it is possible that acute and large reduction in salt intake increases sympathetic activity , stimulates the renin - angiotensin system which would counteract the effects on bp . subsequently , several large - scale intervention studies showing significant antihypertensive effects of salt reduction in diet were performed by several groups . trials of hypertension prevention ( tohp ) phases i and ii were two large randomized controlled trials enrolling 2,182 and 2,382 patients , respectively . in tohp i36 ) , the patients were randomized to three life - style change groups ( weight reduction , sodium reduction , and stress management ) , one of which was a low sodium diet . at 18 months follow - up , weight reduction intervention produced weight loss of 3.9 kg ( p<0.01 ) , diastolic bp change of -2.3mmhg ( p<0.01 ) , and systolic bp change of -2.9mmhg ( p<0.01 ) . sodium reduction interventions also lowered urinary sodium excretion by 44mmol/24 hours ( p<0.01 ) , diastolic bp by 0.9mmhg ( p<0.05 ) , and systolic bp by 1.7mmhg ( p<0.01 ) . they concluded that weight reduction was the most effective strategy tested for reducing bp in normotensive persons . in tohp ii37 ) , from baseline , participants ' sodium excretion decreased 50 and 40mmol / day at 6 and 36 months in the sodium reduction group , respectively . compared with the usual care group , bp decreased 2.9/1.6mmhg in the sodium reduction group , and 4.0/2.8 mmhg in the combined group ( weight and sodium reduction ) at 6 months ( all groups , p<0.001 ) . at 36 months , bp decreases remained greater in the active intervention groups than in the usual care group ( weight loss group , 1.3/0.9mmhg ; sodium reduction group , 1.2/0.7mmhg ; combined group , 1.1/0.6mmhg ) . the long - term , 10- to 15-year trials of hypertension prevention ( tohp ) i and ii show that , apart from lowering bp , net sodium reduction by 44mmol / day ( tohp i ) and 33mmol / day ( toph ii ) leads to significant reduction in cardiovascular events by 25% , even after adjustment for several confounding factors . toph i and ii will presumably remain the best evidence supporting the beneficial effect of a moderate reduction of salt intake in the general population38 ) . the intervention studies of salt intake reduction are often conducted with other life - style modifications . tone study39 ) was performed to determine whether weight loss or reduced sodium intake is effective in the treatment of older persons ( aged 60 to 80 years ) with hypertension . the authors randomized 585 obese participants to reduced sodium intake , weight loss , both , or usual care , and the 390 non - obese participants to reduced sodium intake or usual care . the primary endpoint included high blood pressure after discontinuation of the bp lowering medication at entry ( 190/110 , 170/100 , and 150/90mmhg at 1 , 2 , 3 visits - not adjudicated ) , resuming drug treatment , inability to withdraw treatment , and cardiovascular complications ( angina , myocardial infarction , stroke , heart failure , and coronary revascularization ) . after a median follow - up of 29 months ( range 15 - 36 months ) , the composite outcome occurred less frequently among those assigned vs. not allocated to reduced sodium intake ( hazard ratio 0.69 ; 95% ci , 0.59 - 0.81 ; p<0.001 ) . the mean change in blood pressure for participants assigned to sodium reduction alone was -3.4mmhg systolic and -1.9 mmhg diastolic , and for participants assigned to combined intervention of sodium reduction and weight loss -5.3mmhg systolic and -3.4mmhg diastolic , respectively ( p<0.001 for comparisons to usual care group ) . this study , however , has to be interpreted with caution including selection of adherent and well educated patients ( only 11.1% of pre - screened patients were finally randomized ) and uncertain blinding . there was no difference between sodium - restricted and control patients in the incidence of cardiovascular events ( 44 [ 12.9% ] versus 57 [ 16.7% ] ; p=0.24 ) . the level of salt restriction effective for maintaining a normal bp after the discontinuation of an antihypertensive drug was -5.6 g per day or less . tone study demonstrated that a reduced sodium intake and weight loss , alone or combined , could effectively control hypertension39 ) . another well - conducted landmark study was the dash ( dietary approaches to stop hypertension)-sodium trial40 ) , a 12-week well controlled feeding trial provided the most robust evidence about the effect of salt intake on human bp . it was a multi - centered clinical trial that studied three levels of sodium intake ( 150 , 100 and 50 mmol / day ) on 412 individuals with and without hyper - tension . two different diets that is the control diet and the dash diet , which is rich in fruits , vegetables and low - fat dairy products , were tested . in both groups , the participants were assigned randomly to a high sodium diet ( 150mmol / d ) , normal sodium diet ( 100mmol / d ) , or low sodium diet ( 50mmol / d ) for 30 days and were then crossed over within their assigned groups . when the participants were shifted from a high sodium diet to a normal sodium diet , the systolic bp decreased by 2.1mmhg ( p<0.001 ) in the control group and by 1.3mmhg ( p=0.03 ) in the dash group . when they were shifted from a normal sodium diet to a low sodium diet , there was a further reduction in systolic bp of 4.6mmhg in the control group ( p<0.001 ) and 1.7mmhg in the dash group ( p<0.01 ) . when compared with the controls , the dash diet led to a lower systolic bp of 7.1mmhg in participants without hypertension and 11.5mmhg in participants with hypertension . the adherence to the diet of participants was monitored , not only by measuring 24-hour urine sodium at the end of each period but also their daily food diaries . the study demonstrated that a reduction in salt intake lowered bp both on the control diet and on the dash diet . the combination of a low salt and dash diet had a greater effect on bp than either intervention alone . there was a very significant difference in systolic ( -6.7mmhg ) and diastolic pressure ( -3.5mmhg ) between participants on the 150mmol sodium / day diet and those on the 50mmol sodium / day . there was a greater reduction in systolic pressure when blood pressure was initially high and in women , but most importantly the blood pressure - lowering effect of reducing the salt intake was observed in all categories of the population , in particular in normotensive as well as in hypertensive people . the dash - sodium trial supports that a low sodium diet leads to lower blood pressure . most acknowledge that this study reliably confirmed the benefit of dietary sodium restriction in bp management . however , the dash diet was significantly different from the control diet in terms of more fruits , vegetables , low - fat dairy foods , fish , nuts , potassium , calcium , magnesium , and dietary fiber . although the group on the dash diet had a lower urinary sodium excretion , this does not necessarily imply that the benefit was being solely caused by a dietary sodium reduction . in addition , this study did not evaluate the long - term effects of the intervention and the clinically relevant variables , such as mortality or morbidity . after the dash - sodium trial , many meta - analyses of intervention studies were investigated . in 2002 , he and macgregor41 ) demonstrated that a modest salt intake reduction caused significant falls in bp in both hypertensive and normotensive individuals . in this study , a total of 17 trials in hypertensives ( n=734 ) and 11 trials in normotensives ( n=2,220 ) were included . the median reduction in 24-hour urinary sodium excretion was 78 mmol in hypertensives and 74mmol in normotensives . the pooled estimates of bp fall were 4.96/2.730.40/0.24mmhg in hypertensives ( p<0.001 ) and 2.03/0.970.27/0.21mmhg in normotensives ( p<0.001 ) . weighted linear regression analyses showed a dose response relationship between the change in urinary sodium and bp . a reduction of 100mmol / day in salt intake predicted a fall in bp of 7.11/3.88mmhg ( p<0.001 ) in hypertensives and 3.57/1.66mmhg in normotensive individuals ( p<0.05 ) . they demonstrated that a modest reduction in salt intake for a duration of 4 or more weeks does have a significant and important effect on bp in both hypertensive and normotensive individuals . these findings in conjunction with other previous evidence relating salt intake to bp make a strong case for a reduction in population salt intake , which will lower population bp and therefore reduce cardiovascular mortality . many meta - analyses , so far , on the effect of salt reduction on bp have shown consistent reductions in bp in those with high blood pressure , but there has been some controversy about the magnitude of the fall in bp in normotensive individuals34,36 ) . in these two meta - analyses , it was claimed that salt reduction had no or very little effect on blood pressure in normotensive individuals . however , detailed examination of these two meta - analyses showed that their data collection and analysis were flawed . recently , there has been a hot debate whether current salt intake is too high from a health perspective . there were studies reporting the influence of salt intake on overall cardiovascular diseases such as he et al . he et al.42 ) estimated that reduction of salt intake by 3 g per day lowered systolic blood pressure by 5.6 mmhg in hypertensive individuals . they also found that it was the obese and not the non - obese who benefited . tuomilehto et al.43 ) prospectively followed 1,173 finnish men and 1,263 women aged 25 - 64 years with complete data on 24 hour urinary sodium excretion and cardiovascular risk factors . the hazards ratios for coronary heart disease , cardiovascular disease , and all - cause mortality , associated with a 100mmol increase in 24 hour urinary sodium excretion , were 1.51 ( 95% ci 1.14 - 2.00 ) , 1.45 ( 1.14 - 1.84 ) , and 1.26 ( 1.06 - 1.50 ) , respectively , in both men and women . they concluded that high sodium intake predicted mortality and risk of coronary heart disease , independent of other cardiovascular risk factors , including blood pressure . in a study by o'donnell et al.44 ) , the tendency of an excessive salt intake - induced increase in the incidence of cardiovascular diseases strazzullo et al.45 ) also performed a meta - analysis of prospective cohort studies and reported that excessive salt consumption tended to increase the incidence of cardiovascular diseases . therefore , a salt reduction strategy may be a useful tool for preventing cardiovascular diseases . however , to the contrary , alderman et al.46 ) and cohen et al.47 ) repeatedly suggested that excessive salt reduction increased the incidence of cardiovascular diseases . in the presidential address of the 21 international society of hypertension meeting in 2007 , alderman48 ) advocated that the relationship between salt intake and the risk of cardiovascular diseases is j - shaped and that salt intake at 5 to 6 g per day might be characterized by the lowest risk of cardiovascular diseases . in 2011 , stolarz - skrzypeket al.49 ) reported prospective longitudinal population - based study including 3,681 people without cardiovascular disease at baseline . during a median follow up of 7.9 years , cardiovascular deaths decreased across increasing tertiles of 24-hour sodium excretion . this significant inverse association between cardiovascular mortality and tertile of sodium excretion was retained in multivariable analyses ( p=0.02 ) , with a hr(harzard ratio ) of 1.56 in the low tertile versus the overall risk in the whole study population ( p=0.04 ) . the 24-hour sodium excretion at baseline did not predict either total mortality or fatal combined with nonfatal cardiovascular events . in a subgroup of 1,499 participants who had both bp and sodium excretion measured at baseline and at last follow - up were followed up for a median of 6.1 years . the annual increases in bp averaged 0.37 mmhg systolic and 0.47mmhg diastolic ( p<0.001 ) , but on average the 24-hour urinary sodium excretion did not change over time . however , in multivariable - adjusted analyses of individual participants , a 100-mmol increment in 24-hour sodium excretion was associated with a significant 1.71mmhg increase in systolic bp ( p<0.001 ) , without concomitant change in diastolic bp . they concluded that lower urinary sodium excretion was associated with higher cardiovascular disease ( cvd ) mortality . these findings contradict a large body of evidence that established elevated salt consumption as a risk factor for cvd . however , many researchers including he et al.50 ) criticize the results of this study . in the same year , taylor et al.51 ) published the results of a meta - analysis of intervention studies regarding salt reduction . this meta - analysis involved randomized , control studies of salt reduction in which follow - up was continued for > 6 months ; three of these studies involved normotensive individuals , two hypertensive patients and one normotensive and hypertensive combined subjects . of these , hypertensive and normotensive individuals were separately analyzed . salt reduction was associated with reductions in urinary salt excretion of between 27 and 39mmol per 24 hour and reductions in systolic blood pressure between 1 and 4mmhg . pooled relative risks ( rrs ) comparing the intervention with the reference groups for all - cause mortality were 0.90 ( ci , 0.58 - 1.40 ; 79 deaths ) and 0.96 ( ci , 0.83 - 1.11 ; 565 deaths ) in normotensive and hypertensive participants , respectively . salt restriction increased the risk of all - cause mortality in patients with heart failure ( rr , 2.59 ; ci , 1.04 - 6.44 ; 21 deaths ) . in both hypertensive and normotensive individuals , salt reduction slightly decreased the incidence of cardiovascular diseases , although there was no significant difference . these authors found no strong evidence that salt reduction reduced all - cause mortality or cvd morbidity in normotensives or hypertensives . a single rct showed an increase in the risk of all - cause death in those with congestive heart failure receiving a low - sodium diet . he et al.52 ) simultaneously analyzed normotensive individuals and hypertensive patients from the same studies including taylor 's meta - analysis . they reported that salt reduction at 2.0 to 2.3 g per day significantly decreased the risk of cardiovascular diseases ( 20% of decrease ) . however , in most studies supporting the fact that salt reduction increases the risk of cardiovascular diseases , methodological problems have been indicated47,49 ) , or study subjects were high - risk patients46,51 ) . in conclusion , a moderate reduction of dietary salt intake is generally an effective measure to reduce blood pressure . a reduction in dietary salt from the current intake of 9 - 12 g / day to the recommended level of less than 5 - 6 g / day will have major beneficial effects on cardiovascular health along with major healthcare cost savings around the world . the who strongly recommended to reduce dietary salt intake as one of the top priority actions to tackle the global non - communicable disease crisis and has urged member nations to take action to reduce population wide dietary salt intake to decrease the number of deaths from hypertension , cardiovascular disease and stroke . however , some scientists still advocate the possibility of increased risk of cvd morbidity and mortality at extremes of low salt intake . future research may inform aspects of optimal sodium reduction strategies and the intake targets for populations . until then , we have to continue to build consensus around the greatest benefits of salt reduction for cvd prevention , and dietary salt intake reduction strategies must remain at the top of the public health agenda .