Effect of modest salt reduction on blood pressure: a meta-analysis of randomized trials. Implications for public health

Alcohol, nutrition and health maintenance: selected aspects

In view of the developments in health care relating to the increased prevalence and incidence of chronic diseases and the continuing increase in health-care expenditure, more attention should be paid to health maintenance and disease prevention. Any strategy that can influence health maintenance is of interest, especially lifestyle factors such as nutrition, exercise or stress control. Alcohol has an important place in the daily life of many healthy as well as sick individuals. Alcohol has three major characteristics; it is a nutrient (energy source), a psycho-active drug and a toxin. Each consumer has the choice of which of the characteristics of alcohol he/she wants to utilise. Thus, alcohol represents one of the most important self-implemented disease modifiers in our modern society. The major determinants of the health effects of alcohol are the absolute amount consumed, the consumption frequency, associated lifestyle factors (e.g. smoking, nutrient intake, substrate composition, physical activity pattern) and last, but not least, the genetic background. There are few known disease conditions that have not already been associated positively or negatively with alcohol consumption. The list of diseases includes atherosclerosis, dementia, diabetes, obesity and conditions relating to Zn metabolism. Obesity represents the most important disease modifier in the world and the prevalence rates are increasing rapidly. Evidence suggests that alcohol represents a risk factor for overweight and obesity as a result of specific effects on energy metabolism and substrate metabolism. The potential role of alcohol as an important modulator for the postprandial lipidaemia and its role in the pathogenesis of modern diseases will be discussed.

Very low protein diet supplemented with ketoanalogs improves blood pressure control in chronic kidney disease

Blood pressure (BP) is hardly controlled in chronic kidney disease (CKD). We compared the effect of very low protein diet (VLPD) supplemented with ketoanalogs of essential amino acids (0.35 g/kg/day), low protein diet (LPD, 0.60 g/kg/day), and free diet (FD) on BP in patients with CKD stages 4 and 5. Vegetable proteins were higher in VLPD (66%) than in LPD (48%). LPD was prescribed to 110 consecutive patients; after run-in, they were invited to start VLPD. Thirty subjects accepted; 57 decided to continue LPD; 23 refused either diet (FD group). At baseline, protein intake (g/kg/day) was 0.79+/-0.09 in VLPD, 0.78+/-0.11 in LPD, and 1.11+/-0.18 in FD (P<0.0001). After 6 months, protein intake was lower in VLPD than LPD and FD (0.54+/-0.11, 0.78+/-0.10, and 1.04+/-0.21 g/kg/day, respectively; P<0.0001). BP diminished only in VLPD, from 143+/-19/84+/-10 to 128+/-16/78+/-7 mm Hg (P<0.0001), despite reduction of antihypertensive drugs (from 2.6+/-1.1 to 1.8+/-1.2; P<0.001). Urinary urea excretion directly correlated with urinary sodium excretion, which diminished in VLPD (from 181+/-32 to 131+/-36 mEq/day; P<0.001). At multiple regression analysis (R2=0.270, P<0.0001), BP results independently related to urinary sodium excretion (P=0.023) and VLPD prescription (P=0.003), but not to the level of protein intake. Thus, in moderate to advanced CKD, VLPD has an antihypertensive effect likely due to reduction of salt intake, type of proteins, and ketoanalogs supplementation, independent of actual protein intake.

Management of hypertension in chronic kidney disease

Optimal blood pressure control (<130/80 mm Hg) in patients with chronic kidney disease (CKD), despite being the main objective of conservative therapy, is rarely achieved in clinical practice. A major area of improvement is the correction of the extracellular volume expansion. This goal can be reached by means of dietary salt restriction (100 mEq/d of NaCl). If this intervention fails, hypertension can be treated by thiazide diuretics in patients with mild CKD, whereas loop diuretics at adequate doses are indicated in patients with more advanced CKD. Angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are more effective than other drugs in slowing progression of proteinuric diabetic and nondiabetic CKD. However, the control rates of blood pressure are usually inadequate with antihypertensive therapy including only these drugs; therefore, addition of other classes of antihypertensive drugs is often required.

Dietetic guidelines on food and nutrition in the secondary prevention of cardiovascular disease ? evidence from systematic reviews of randomized controlled trials (second update, January 2006)

AIM

To update dietetic guidelines based on systematic review evidence on dietary advice to prevent further events in people with existing cardiovascular disease (CVD) (secondary prevention).

METHODS

The Cochrane Library, MEDLINE and EMBASE were comprehensively searched to January 2005 for systematic reviews on aspects of diet and heart health. Reviews were included if they searched systematically for randomized controlled trials relating to diet and secondary prevention of CVD. Each review was critically appraised by at least two members of the UK Heart Health and Thoracic Dietitians Group. The quality and results of each review were discussed and summarized at a group meeting.

RESULTS

Evidence-based strategies that reduce cardiovascular events in those with CVD include reduction in saturated fat and substitution with unsaturated fats. Individuals who have suffered a myocardial infarction may also benefit from adopting a Mediterranean type diet and increasing intake of omega 3 fats, but it is not clear whether they are beneficial for all patients with CVD. There is no systematic review evidence to support the use of antioxidant vitamins supplements, low glycaemic index diets, or homocysteine lowering therapies in this group.

CONCLUSION

There remains good evidence that reducing saturated fat reduces morbidity in patients with CVD. This advice is consistent for most manifestations of CVD, with the addition of Mediterranean dietary advice and increased omega 3 fats for those who have had a myocardial infarction.

Sodium intake and hypertension

In current diets, the level of sodium is very high, whereas that of potassium, calcium, and magnesium is low compared with the level in diets composed of unprocessed, natural foods. We present the biologic rationale and scientific evidence that show that the current salt intake levels largely explain the high prevalence of hypertension. Comprehensive reduction of salt intake, both alone and particularly in combination with increases in intakes of potassium, calcium, and magnesium, is able to lower average blood pressure levels substantially. During the past 30 years, the one-third decrease in the average salt intake has been accompanied by a more than 10-mm Hg fall in the population average of both systolic and diastolic blood pressure, and a 75% to 80% decrease in both stroke and coronary heart disease mortality in Finland. There is no evidence of any harmful effects of salt reduction. Salt-reduction recommendations alone have a very small, if any, population impact. In the United States, for example, the per capita use of salt increased by approximately 55% from the mid-1980s to the late 1990s. We deal with factors that contribute toward increasing salt intakes and present examples of the methods that have contributed to the successful salt reduction in Finland.

Nonpharmacologic therapy for hypertension: Does it really work?

Nondrug therapy of hypertension really does work but requires strong motivation by both patient and physician. In addition to global health benefits, prescription of weight loss, exercise, moderation of salt and alcohol intake, Dietary Approach to Stop Hypertension (DASH) eating plan, and tobacco avoidance can decrease the risk for normotensive and prehypertensive patients of developing fixed hypertension. Initiating and maintaining a healthy lifestyle may be sufficient to avoid pharmacologic therapy for some patients and is a valuable adjunct to drug therapy for most. Blood pressure lowering can be achieved by weight reduction (5-20 mm Hg/10 kg), DASH eating plan (8-14 mm Hg), dietary sodium reduction (2-8 mm Hg), increased physical activity (4-9 mm Hg), and moderation of alcohol consumption (2-4 mm Hg). Combination of two or more modalities may have an additive benefit. Cessation of tobacco abuse not only has global health benefits, but may reduce blood pressure.

Gender and obesity influence sodium intake and fluid regulation in Zucker rats following repeated sodium depletions

The Zucker obese rat is an important model for the metabolic syndrome, which includes renal disease and salt-sensitive hypertension, suggesting abnormalities of body fluid regulation. Here, in Zucker rats, lean and obese, and of both sexes, we compared 48 h of sodium intake and fluid regulation responses with repeated depletions with furosemide to repeated control saline injections. Increased urine volume excretion was observed after each furosemide administration for the 4 groups and obese rats excreted more than the leans on the control days. Male obese rats did not excrete sodium nor increase intake of 2% NaCl following the first furosemide administration, whereas the other 3 groups did. Subsequent depletions increased 2% NaCl consumption and urinary sodium excretion in all groups. Males excreted more sodium in their urine than the females on the control days. Females showed an increase in 2% NaCl intake on control days. Water intake increased in the female leans after each depletion, increased in the males after the 2nd and 3rd depletion and increased in the obese females only after the 2nd depletion. These findings show clearly that there are gender- and weight-related differences in the response of Zucker rats to furosemide-induced depletion. However, the main differences occurred with the first depletion. With repeated depletions the rats adjusted sodium and fluid intake and excretion so that differences due to gender and body weight tended to disappear. Our findings caution against drawing conclusions about differences due to gender and body weight based on single treatments.

Importance of salt in determining blood pressure in children: meta-analysis of controlled trials

To assess the effect of reducing salt intake on blood pressure in children, we carried out a meta-analysis of controlled trials. Trials were included if participants were children (< or = 18 years), and duration of salt reduction must have been for > or = 2 weeks. Mean effect size was calculated using a fixed-effect model, because there was no significant heterogeneity. Ten trials of children and adolescents with 966 participants were included (median age: 13 years; range: 8 to 16 years; median duration: 4 weeks; range: 2 weeks to 3 years). Salt intake was reduced by 42% (interquartile range [IQR]: 7% to 58%). There were significant reductions in blood pressure: systolic: -1.17 mm Hg (95% CI: -1.78 to -0.56 mm Hg; P<0.001); diastolic: -1.29 mm Hg (95% CI: -1.94 to -0.65 mm Hg; P<0.0001). Three trials of infants with 551 participants were included (median duration: 20 weeks; range: 8 weeks to 6 months). Salt intake was reduced by 54% (IQR: 51% to 79%). There was a significant reduction in systolic blood pressure: -2.47 mm Hg (95% CI: -4.00 to -0.94 mm Hg; P<0.01). This is the first meta-analysis of salt reduction in children, and it demonstrates that a modest reduction in salt intake causes immediate falls in blood pressure and, if continued, may well lessen the subsequent rise in blood pressure with age. This would result in major reductions in cardiovascular disease. These results in conjunction with other evidence provide strong support for a reduction in salt intake in children.

Les mesures nutritionnelles dans l’hypertension artérielle

Nutritional factors may explain 30-75% of cases of hypertension, depending on the population. Overweight alone can explain 11-25%. Nutritional measures are effective in reducing blood pressure or delaying the onset of hypertension. Globally, their impact is close to that of antihypertensive treatment with a single drug and they potentiate the drug's efficacy. The Dash diet, in particular, has been shown to be effective in lowering blood pressure. It is low in saturated fat and sodium, rich in fruit, vegetables and nonfat dairy products.

Blood pressure change in a free-living population-based dietary modification study in Japan

OBJECTIVE

To assess whether dietary intervention in free-living healthy subjects is effective in improving blood pressure levels.

DESIGN

Open randomised, controlled trial.

SETTING

Free-living healthy subjects in two rural villages in north-eastern Japan.

PARTICIPANTS

Five hundred and fifty healthy volunteers aged 40-69 years.

INTERVENTIONS

Tailored dietary education to encourage a decrease in sodium intake and an increase in the intake of vitamin C and carotene, and of fruit and vegetables.

MAIN OUTCOME MEASURES

Blood pressure, dietary intake and urinary excretion of sodium, dietary carotene and vitamin C, and fruit and vegetable intake data were collected at 1 year after the start of the intervention.

RESULTS

During the first year, changes differed significantly between the intervention and control groups for dietary (P = 0.002) and urinary excretion (P < 0.001) of sodium and dietary vitamin C and carotene (P = 0.003). Systolic blood pressure decreased from 127.9 to 125.2 mmHg (2.7 mmHg decrease; 95% confidence interval, -4.6 to -0.8) in the intervention group, whereas it increased from 128.0 to 128.5 mmHg (0.5 increase; -1.3 to 2.3) in the control group. This change was statistically significant (P = 0.007). In contrast, the change in diastolic blood pressure did not significantly differ between the groups. In hypertensive subjects, a significant difference in systolic blood pressure reduction was seen between the groups (P = 0.032).

CONCLUSION

Moderate-intensity dietary counseling in free-living healthy subjects achieved significant dietary changes, which resulted in a significant decrease in systolic blood pressure.

Sodium in the Finnish diet: II trends in dietary sodium intake and comparison between intake and 24-h excretion of sodium

OBJECTIVE

To estimate cross-sectional and long-term dietary sodium intakes and sources in Finland, and to evaluate the validity of 48-h recall to assess sodium intake.

DESIGN

Cross-sectional dietary surveys and food availability data (Food Balance Sheets).

SETTING

Dietary surveys were carried out in Finland in 1992, 1997 and 2002. Food availability data were collected from 1980 to 1999.

SUBJECTS

A stratified random sample was drawn from the population register. The total number of participants in the three dietary surveys was 6730. In the subsample for urine collection, the number of participants was 879.

INTERVENTIONS

Nutrient intakes were estimated on the basis of a 3-day food diary in 1992, a 24-h recall in 1997 and a 48-h recall in 2002. The 24-h urinary excretion of sodium was used to validate sodium intake. In addition, salt intake was estimated based on Food Balance Sheets.

RESULTS

Sodium intake has slowly decreased since the early 1980s. Reported daily sodium intake correlated significantly with sodium excretion.

CONCLUSIONS

Sodium intake has decreased during the last two decades, but is still higher than the recommended daily intake. Sodium intake estimation based on dietary surveys and food availability data is a valid method provided that the food composition database is up to date and of good quality.

SPONSORSHIP

All surveys were funded by the National Public Health Institute in Finland and the Ministry of Social Affairs and Health.

Blood pressure response to 1-month, electrolyte-carbohydrate beverage consumption

There are many occupations where workers undergo daily exposure to rigorous environments, often with only limited access to fluids. Such conditions warrant the use of an electrolyte rehydration beverage; however, the long-term use of such beverages may pose potential health risks due to the increase in dietary sodium intake. This study proposed to determine blood pressure response to daily electrolyte-beverage consumption during strenuous work in a group of young normotensive workers. Three groups of tree planters (mean age = 23 +/- 3 years, n = 51) were provided with electrolyte-beverage (3 mmol/L potassium, 18 mmol/L sodium), electrolyte-carbohydrate-beverage (addition of 333 mmol/L carbohydrate to electrolyte-beverage), or water at a rate of 500 mL/hour during the working day. Systolic and diastolic blood pressures were measured each week over the course of 23 working days (30 days total elapsed time). Planters spent 8.4 +/- 1.0 hours/day at heart rates of 124 +/- 10 b/min. There were no differences between the groups for volume of fluid consumed; however, the electrolyte beverages appeared to be more effective than water at maintaining hydration during planting. Daily sodium intake approximated estimated losses in all groups, with total intake lowest in the water group. Resting plasma volume expanded by approximately 4% in all groups, from the first to the 30th day. No changes were observed over time for systolic or diastolic blood pressure. One month of daily consumption of approximately 4.5 L of electrolyte-beverage or electrolyte-carbohydrate-beverage did not appear to affect resting blood pressure in young normotensive workers engaged in heavy physical work.

Sodium in the Finnish diet: 20-year trends in urinary sodium excretion among the adult population

OBJECTIVE

High sodium intake increases the risk of cardiovascular diseases and may also be associated with higher rates of stomach cancer, asthma disorders and infections. In Finland, cross-sectional population surveys to monitor cardiovascular risk factors have been carried out since the 1970s. The main aim of this paper is to present trends in urinary sodium and potassium excretion from 1979 to 2002.

DESIGN

Cross-sectional population surveys on cardiovascular risk factors.

SETTING

Surveys were carried out in Finland in 1979, 1982, 1987 and 2002 in four geographical areas: North Karelia, the Kuopio area, Southwestern Finland and the Helsinki area.

SUBJECTS

For each survey a random sample stratified by age and sex was drawn from the population register. In this analysis, participants of urine collection subsamples aged 25-64 years (n = 4648) were included.

INTERVENTIONS

A 24-h urinary collection was carried out in subsamples (n = 2218-2487) in connection with population risk factor surveys. Urinary sodium and potassium concentrations were analyzed in the same laboratory throughout, using a flame photometer in 1979, 1982 and 1987 and an ion-selective electrode in 2002.

RESULTS

Between 1979 and 2002 urinary sodium excretion in Finland decreased from over 220 to less than 170 mmol/day among men and from nearly 180 to less than 130 mmol/day among women. Although potassium excretion decreased somewhat as well, the decrease in sodium-potassium molar ratio was also significant.

CONCLUSIONS

The 24-h urinary sodium excretion in Finland has decreased significantly during the last 20 years. However, excretion levels are still considerably higher than recommendations. A further decrease in sodium intake remains a goal for the Finnish food industry and consumers.

SPONSORSHIP

All surveys were funded by the National Public Health Institute in Finland.

Dietary Approaches to Prevent and Treat Hypertension

A substantial body of evidence strongly supports the concept that multiple dietary factors affect blood pressure (BP). Well-established dietary modifications that lower BP are reduced salt intake, weight loss, and moderation of alcohol consumption (among those who drink). Over the past decade, increased potassium intake and consumption of dietary patterns based on the "DASH diet" have emerged as effective strategies that also lower BP. Of substantial public health relevance are findings related to blacks and older individuals. Specifically, blacks are especially sensitive to the BP-lowering effects of reduced salt intake, increased potassium intake, and the DASH diet. Furthermore, it is well documented that older individuals, a group at high risk for BP-related cardiovascular and renal diseases, can make and sustain dietary changes. The risk of cardiovascular disease increases progressively throughout the range of BP, beginning at 115/75 mm Hg. In view of the continuing epidemic of BP-related diseases and the increasing prevalence of hypertension, efforts to reduce BP in both nonhypertensive and hypertensive individuals are warranted. In nonhypertensive individuals, dietary changes can lower BP and prevent hypertension. In uncomplicated stage I hypertension (systolic BP of 140 to 159 mm Hg or diastolic BP of 90 to 99 mm Hg), dietary changes serve as initial treatment before drug therapy. In those hypertensive patients already on drug therapy, lifestyle modifications, particularly a reduced salt intake, can further lower BP. The current challenge to healthcare providers, researchers, government officials, and the general public is developing and implementing effective clinical and public health strategies that lead to sustained dietary changes among individuals and more broadly among whole populations.

A community programme to reduce salt intake and blood pressure in Ghana [ISRCTN88789643]

BACKGROUND

In Africa hypertension is common and stroke is increasing. Detection, treatment and control of high blood pressure (BP) is limited. BP can be lowered by reducing salt intake. In Africa salt is added to the food by the consumer, as processed food is rare. A population-wide approach with programmes based on health education and promotion is thus possible.

METHODS

We carried out a community-based cluster randomised trial of health promotion in 1,013 participants from 12 villages (628 women, 481 rural dwellers); mean age 55 years to reduce salt intake and BP. Average BP was 125/74 mmHg and urinary sodium (UNa) 101 mmol/day. A health promotion intervention was provided over 6 months to all villages. Assessments were made at 3 and 6 months. Primary end-points were urinary sodium excretion and BP levels.

RESULTS

There was a significant positive relationship between salt intake and both systolic (2.17 mmHg [95% CI 0.44 to 3.91] per 50 mmol of UNa per day, p < 0.001) and diastolic BP (1.10 mmHg [0.08 to 1.94], p < 0.001) at baseline. At six months the intervention group showed a reduction in systolic (2.54 mmHg [-1.45 to 6.54]) and diastolic (3.95 mmHg [0.78 to 7.11], p = 0.015) BP when compared to control. There was no significant change in UNa. Smaller villages showed greater reductions in UNa than larger villages (p = 0.042). Irrespective of randomisation, there was a consistent and significant relationship between change in UNa and change in systolic BP, when adjusted for confounders. A difference in 24-hour UNa of 50 mmol was associated with a lower systolic BP of 2.12 mmHg (1.03 to 3.21) at 3 months and 1.34 mmHg (0.08 to 2.60) at 6 months (both p < 0.001).

CONCLUSION

In West Africa the lower the salt intake, the lower the BP. It would appear that a reduction in the average salt intake in the whole community may lead to a small but significant reduction in population systolic BP.

Controversies in hypertension

Hypertension remains the most common risk factor for cardiovascular morbidity and mortality. Its incidence is rising in both ageing and obese populations, but its control remains inadequate worldwide. We address several persisting controversies that may interfere with appropriate management of hypertension. They include: the reasons behind the increasing incidence of hypertension and the possible ways to slow the process, especially by lifestyle changes; the need for overall cardiovascular risk assessment; the major issues in the decision to institute drug therapy and the choice of drugs; and the importance of screening for various identifiable causes. We provide the background for these controversies, followed by some opinions on how to guide practitioners to offer more effective management of hypertension.

Salt and Blood Pressure: Time to Challenge

Hypertension is a worldwide epidemic and its control is costly, but still inadequate. The mechanisms underlying the development of primary hypertension remain elusive. Several observations point to the kidney as a primary actor and sodium as the main culprit for development of hypertension. Over the last few decades, experimental, observational and clinical data have continuously indicated that excess salt intake is positively associated with elevated blood pressure and that blood pressure can be significantly reduced with substantial reductions in dietary sodium. This review highlights the pathophysiological mechanisms linking sodium to elevated blood pressure, synthesizes available evidence for the effect of reducing salt intake in controlling blood pressure. It specifically analyzes 6 recent meta-analyses and dietary approaches to stop hypertension.

Why and how to implement sodium, potassium, calcium, and magnesium changes in food items and diets?

The present average sodium intakes, approximately 3000-4500 mg/day in various industrialised populations, are very high, that is, 2-3-fold in comparison with the current Dietary Reference Intake (DRI) of 1500 mg. The sodium intakes markedly exceed even the level of 2500 mg, which has been recently given as the maximum level of daily intake that is likely to pose no risk of adverse effects on blood pressure or otherwise. By contrast, the present average potassium, calcium, and magnesium intakes are remarkably lower than the recommended intake levels (DRI). In USA, for example, the average intake of these mineral nutrients is only 35-50% of the recommended intakes. There is convincing evidence, which indicates that this imbalance, that is, the high intake of sodium on one hand and the low intakes of potassium, calcium, and magnesium on the other hand, produce and maintain elevated blood pressure in a big proportion of the population. Decreased intakes of sodium alone, and increased intakes of potassium, calcium, and magnesium each alone decrease elevated blood pressure. A combination of all these factors, that is, decrease of sodium, and increase of potassium, calcium, and magnesium intakes, which are characteristic of the so-called Dietary Approaches to Stop Hypertension diets, has an excellent blood pressure lowering effect. For the prevention and basic treatment of elevated blood pressure, various methods to decrease the intake of sodium and to increase the intakes of potassium, calcium, and magnesium should be comprehensively applied in the communities. The so-called 'functional food/nutraceutical/food-ceutical' approach, which corrects the mineral nutrient composition of extensively used processed foods, is likely to be particularly effective in producing immediate beneficial effects. The European Union and various governments should promote the availability and use of such healthier food compositions by tax reductions and other policies, which make the healthier choices cheaper than the conventional ones. They should also introduce and promote the use of tempting nutrition and health claims on the packages of healthier food choices, which have an increased content of potassium, calcium, and/or magnesium and a lowered content of sodium. Such pricing and claim methods would help the consumers to choose healthier food alternatives, and make composition improvements tempting also for the food industry.

Modest salt reduction lowers blood pressure in isolated systolic hypertension and combined hypertension

Many randomized trials have shown that a reduction in salt intake lowers blood pressure in hypertensive individuals. However, few have looked at the effects according to hypertension category. A recent analysis of the third and fourth National Health and Nutrition Examination Survey suggests that salt intake may not be related to blood pressure in isolated systolic or combined hypertension. To look at this further, we reanalyzed the data of our previous salt reduction trials. Hypertensive individuals were studied in randomized double-blind crossover studies: 1 month of usual salt intake compared with 1 month of reduced salt intake. In isolated systolic hypertension (n=24), blood pressure was reduced from 166+/-19/86+/-7 to 156+/-20/85+/-7 mm Hg (systolic P<0.001; diastolic P=0.459) with a reduction in urinary sodium from 175+/-51 to 87+/-38 mmol per 24-hour period (10.3 to 5.1 g per day of salt). In combined hypertension (n=88), blood pressure was reduced from 161+/-16/100+/-9 to 154+/-17/96+/-9 mm Hg (P<0.001) with a reduction urinary sodium from 176+/-65 to 98+/-51 mmol per 24-hour period (10.4 to 5.8 g per day of salt). These results demonstrate that salt reduction has a significant effect on blood pressure in isolated systolic and combined hypertension. The fall in systolic observed in isolated systolic hypertension would be predicted to reduce stroke by approximately one third, ischemic heart disease by one quarter, and heart failure by one quarter in the population between 60 and 80 years of age, in whom isolated systolic hypertension is the predominate form of hypertension and carries the highest risk. These results provide strong support for universal salt reduction in all hypertensives.

Plasma sodium and hypertension

Dietary salt is the major cause of the rise in the blood pressure with age and the development of high blood pressure in populations. However, the mechanisms whereby salt intake raises the blood pressure are not clear. Existing concepts focus on the tendency for an increase in extracellular fluid volume (ECV), but an increased salt intake also induces a small rise in plasma sodium, which increases a transfer of fluid from the intracellular to the extracellular space, and stimulates the thirst center. Accordingly, the rise in plasma sodium is responsible for the tendency for an increase in ECV. Although the change in ECV may have a pressor effect, the associated rise in plasma sodium itself may also cause the blood pressure to rise. There is some evidence in patients with essential hypertension and the spontaneously hypertensive rat (SHR) that plasma sodium may be raised by 1 to 3 mmol/L. An experimental rise in sodium concentration greater than 5 mmol/L induces pressor effects on the brain and on the renin-angiotensin system. Such a rise can also induce changes in cultured vascular tissue similar to those that occur in the vessels of humans and animals on a high sodium diet, independent of the blood pressure. We suggest that a small increase in plasma sodium may be part of the mechanisms whereby dietary salt increases the blood pressure.

Links between dietary salt intake, renal salt handling, blood pressure, and cardiovascular diseases

Epidemiological, migration, intervention, and genetic studies in humans and animals provide very strong evidence of a causal link between high salt intake and high blood pressure. The mechanisms by which dietary salt increases arterial pressure are not fully understood, but they seem related to the inability of the kidneys to excrete large amounts of salt. From an evolutionary viewpoint, the human species is adapted to ingest and excrete <1 g of salt per day, at least 10 times less than the average values currently observed in industrialized and urbanized countries. Independent of the rise in blood pressure, dietary salt also increases cardiac left ventricular mass, arterial thickness and stiffness, the incidence of strokes, and the severity of cardiac failure. Thus chronic exposure to a high-salt diet appears to be a major factor involved in the frequent occurrence of hypertension and cardiovascular diseases in human populations.

Decreasing population blood pressure: 15 years of follow-up in the Copenhagen City Heart Study (CCHS)

OBJECTIVE

Population blood pressure (BP) levels from a longitudinal study were analysed for trends during a period of 15 years. Trends from unadjusted data are reported as well as trends adjusted for major cardiovascular (CV) risk factors and use of antihypertensive therapy, thus allowing assessment of independent BP trends.

DESIGN

The Copenhagen City Heart Study is a longitudinal epidemiological study of CV risk in a random population sample of both genders aged 20 and above. Three cross-sectional population surveys were performed: 1976-78 (n=14000), 1981-83 (n=12675) and 1991-94 (n=9661).

METHODS

BP was measured by a London School of Hygiene Sphygmomanometer. Weight and height were measured and body mass index (BMI) calculated. Non-fasting plasma cholesterol was determined. A questionnaire concerning smoking status and diabetes was completed. Measurement methods were strictly standardized and unchanged in the three cross-sectional surveys.

RESULTS

Unadjusted systolic BP (SBP) levels decreased during 15 years of follow-up, and unadjusted diastolic BP (DBP) levels increased. An investigation of the effect of major CV risk factors, both singly and jointly on BP levels, revealed a pattern of correlations contributing to BP variability. Adjustments for BMI, cholesterol, diabetes, use of antihypertensive therapy and smoking status were made in the final analyses of BP trend. The adjusted trend model demonstrated that SBP levels remained lower than SBP levels in the first survey. DBP levels increased slightly.

CONCLUSIONS

The results demonstrate a decrease in population SBP. The decrease is independent of major CV risk factors. Possible contributing factors are discussed.

Effects of a low sodium diet on bone metabolism

Osteoporosis is a serious public health problem, and dietary interventions may potentially be helpful in preventing this disorder. The purpose of this study was to determine the effects of a low sodium diet on bone metabolism in postmenopausal women. This was a longitudinal study to determine the effects of a low sodium (2-g/day) diet on bone. Forty postmenopausal African-American and Caucasian women were enrolled in a 2-g/day sodium diet for 6 months. Sodium and calcium excretion, bone turnover, and calcitropic hormones (intact parathyroid hormone (PTH) and 1,25 dihydroxyvitamin D) were measured before and 6 months after the intervention. In women who had baseline sodium excretions equal to or greater than the average sodium intake in the United States (> or =3.4 g/day), the low sodium diet resulted in significant decreases in sodium excretion (P = 0.01), in calcium excretion (P = 0.01), and in a biomarker of bone turnover, aminoterminal propeptide of type I collagen (P = 0.04). However, there were no significant changes in calcitropic hormones, including intact PTH (P = 0.97) or 1,25 dihydroxyvitamin D (P = 0.49) with the low sodium diet. These findings suggest that in postmenopausal women with sodium intakes > or =3.4 g/day, a low sodium diet may have benefits for skeletal health.

Plasma sodium: ignored and underestimated

Salt intake is a major regulator of blood pressure. There is evidence that those who develop high blood pressure have an underlying defect in the ability of the kidney to excrete salt. It has been suggested that this results in a greater tendency to retain sodium and an increased compensatory response that is responsible for the rise in blood pressure. There is also evidence suggesting that small increases in plasma sodium may directly affect blood pressure, independent of the associated expansion in extracellular volume. We reanalyzed 3 types of studies of changing salt intake. (1) An acute and large reduction in salt intake from 350 mmol/d to 10 to 20 mmol/d for 5 days in hypertensives and normotensives was associated with a fall in plasma sodium of approximately 3 mmol/L (P<0.001). (2) Progressive increases in salt intake from 10 to 250 mmol/d by a daily amount of 50 mmol in normotensives caused increases in plasma sodium (P<0.001). (3) Longer-term modest reduction in salt intake in hypertensives was studied in double-blind randomized crossover studies; 1 month of usual salt intake ( approximately 170 mmol/d) compared with reduced salt intake ( approximately 100 mmol/d). There was a decrease in plasma sodium of 0.4+/-0.2 mmol/L (P<0.05), which was weakly but significantly correlated with the fall in systolic blood pressure (r=0.18; P<0.05). These studies demonstrate that an increase or a decrease in salt intake causes changes in plasma sodium. Small changes in plasma sodium alter extracellular volume, which may influence blood pressure. Changes in plasma sodium may also affect blood pressure directly.

Blood pressure and urinary sodium in men and women: the Norfolk Cohort of the European Prospective Investigation into Cancer (EPIC-Norfolk)

BACKGROUND

Abundant evidence indicates that a high sodium intake is causally related to high blood pressure, but debate over recommendations to reduce dietary sodium in the general population continues. A key issue is whether differences in usual sodium intake within the range feasible in free-living populations have clinical or public health relevance.

OBJECTIVE

We examined the relation between blood pressure and urinary sodium as a marker of dietary intake.

DESIGN

This was a study of 23104 community-living adults aged 45-79 y.

RESULTS

Mean systolic and diastolic blood pressure increased as the ratio of urinary sodium to creatinine increased (as estimated from a casual urine sample), with differences of 7.2 mm Hg for systolic blood pressure and 3.0 mm Hg for diastolic blood pressure (P < 0.0001) between the top and bottom quintiles. This trend was independent of age, body mass index, urinary potassium:creatinine, and smoking and was consistent by sex and history of hypertension. The prevalence of those with systolic blood pressure >/= 160 mm Hg halved from 12% in the top quintile to 6% in the bottom quintile; the odds ratio for having systolic blood pressure >/= 160 mm Hg was 2.48 (95% CI: 1.90, 3.22) for men and 2.67 (95% CI: 2.08, 3.43) for women in the top compared with the bottom quintile of urinary sodium. Estimated mean sodium intakes in the lowest and highest quintiles were approximately 80 and 220 mmol/d, respectively.

CONCLUSIONS

Within the usual range found in a free-living population, differences in urinary sodium, an indicator of dietary sodium intake, are associated with blood pressure differences of clinical and public health relevance. Our findings reinforce recommendations to lower average sodium intakes in the general population.

Dietetic guidelines: diet in secondary prevention of cardiovascular disease (first update, June 2003)

AIM

To update dietetic guidelines summarizing the systematic review evidence on dietary advice to prevent further events in people with existing cardiovascular disease (CVD) (secondary prevention).

METHODS

The Cochrane Library, MEDLINE and EMBASE were comprehensively searched to November 2002 for systematic reviews on aspects of diet and heart health. Reviews were included if they searched systematically for randomised controlled trials relating to diet and secondary prevention of CVD. Two members of the UK Heart Health and Thoracic Dietitians Group critically appraised each review. The quality and results of each review were discussed and summarized in a meeting of the whole group.

RESULTS

Providing evidence-based dietary information (including increasing omega-3 fat intake) to all people who have had a myocardial infarction will save more lives than concentrating dietary advice on just those in need of weight loss or lipid lowering. The practice of prioritizing dietetic time in secondary prevention to those with raised lipids is out of date since the advent of statin therapy. However, effective dietary advice for those with angina, stroke, peripheral vascular disease or heart failure is less clear.

CONCLUSION

There is good systematic review evidence that dietary advice to those with coronary heart disease can reduce mortality and morbidity as well as modify some risk factors. Dietary advice that does this most effectively should be prioritized.

Dose–response of sodium excretion and blood pressure change among overweight, nonhypertensive adults in a 3-year dietary intervention study

A cross-sectional dose-response relationship between sodium intake and blood pressure (BP) has been demonstrated, but evidence for a graded longitudinal effect is limited. Evaluation of BP response to sodium reduction was assessed in a 3-year lifestyle dietary intervention trial. BP changes at 18 and 36 months after enrollment were analysed according to concurrent quantitative changes in sodium excretion and by categories of success in sodium reduction among 1157 men and women, ages 30-54 years, with a diastolic BP (DBP) 83-89 mmHg, systolic BP (SBP) <140 mmHg, body weight 110-165% of sex-specific standard weight, and valid baseline urinary sodium excretion. Participants were randomized to a Sodium Reduction intervention (n=581) or Usual Care (n=576). From a 187 mmol/24 h baseline mean sodium excretion, net decreases were 44 mmol/24 h at 18 months and 38 mmol/24 h at 36 months in Sodium Reduction vs Usual Care. Corresponding net decreases in SBP/DBP were 2.0/1.4 mmHg at 18 months, and 1.7/0.9 mmHg at 36 months. Significant dose-response trends in BP change over quintiles of achieved sodium excretion were seen at both 18 (SBP and DBP) and 36 (SBP only) months; effects appeared stronger among those maintaining sodium reduction. Estimated SBP decreases per 100 mmol/24 h reduction in sodium excretion at 18 and 36 months were 2.2 and 1.3 mmHg before and 7.0 and 3.6 mmHg after correction for measurement error, respectively. DBP changes were smaller and nonsignificant at 36 months. In conclusion, incremental decreases in BP with lower sodium excretion were observed in these overweight nonhypertensive individuals.

Blood pressure response to dietary modifications in free-living individuals

A diet rich in fruits, vegetables, and low-fat dairy foods has been shown to lower blood pressure (BP) when all foods are provided. We compared the effect on BP (measured at home) of 2 different self-selected diets: a low-sodium, high-potassium diet, rich in fruit and vegetables (LNAHK) and a high-calcium diet rich in low-fat dairy foods (HC) with a moderate-sodium, high-potassium, high-calcium DASH-type diet, high in fruits, vegetables and low-fat dairy foods (OD). Subjects were randomly allocated to 2 test diets for 4 wk, the OD and either LNAHK or HC diet, each preceded by a 2 wk control diet (CD). The changes in BP between the preceding CD period and the test diet period (LNAHK or HC) were compared with the change between the CD and the OD periods. Of the 56 men and 38 women that completed the OD period, 43 completed the LNAHK diet period and 48 the HC diet period. The mean age was 55.6 +/- 9.9 (+/-SD) years. There was a fall in systolic pressure between and the CD and OD [-1.8 +/- 0.5 mm Hg (P < 0.001)]. Compared with OD, systolic and diastolic BPs fell during the LNAHK diet period [-3.5 +/- 1.0 (P < 0.001) and -1.9 +/- 0.7 (P < 0.05) mmHg, respectively] and increased during the HC diet period [+3.1 +/- 0.9 (P < 0.01) and +0.8 +/- 0.6 (P = 0.15) mm Hg, respectively]. A self-selected low-sodium, high-potassium diet resulted in a greater fall in BP than a multifaceted OD, confirming the beneficial effect of dietary intervention on BP in a community setting.

Volume natriuresis vs. pressure natriuresis

Body fluid regulation depends on regulation of renal excretion. This includes a fast vasopressin-mediated water-retaining mechanism, and slower, complex sodium-retaining systems dominated by the renin-angiotensin aldosterone cascade. The sensory mechanisms of sodium control are not identified; effectors may include renal arterial pressure, renal reflexes, extrarenal hormones and other regulatory factors. Since the pioneering work of Guyton more than three decades ago, pressure natriuresis has been in focus. Dissociations between sodium excretion and blood pressure are explained as conditions where regulatory performance exceeds the precision of the measurements. It is inherent to the concept, however, that sudden transition from low to high sodium intake elicits an arterial pressure increase, which is reversed by the pressure natriuresis mechanism. However, such transitions elicit parallel changes in extracellular fluid volume thereby activating volume receptors. Recently we studied the orchestration of sodium homeostasis by chronic and acute sodium loading in normal humans and trained dogs. Small increases in arterial blood pressure are easily generated by acute sodium loading, and dogs appear more sensitive than humans. However, with suitable loading procedures it is possible - also acutely - to augment renal sodium excretion by at least one order of magnitude without any change in arterial pressure whatsoever. Although pressure natriuresis is a powerful mechanism capable of overriding any other controller, it seems possible that it is not operative under normal conditions. Consequently, it is suggested that physiological control of sodium excretion is neurohumoral based on extracellular volume with neural control of renin system activity as an essential component.

Decreasing dietary sodium while following a self-selected potassium-rich diet reduces blood pressure

Reducing dietary sodium reduces blood pressure (BP), a major risk factor for cardiovascular disease, but few studies have specifically examined the effect on BP of altering dietary sodium in the context of a high potassium diet. This randomized, crossover study compared BP values in volunteer subjects self-selecting food intake and consuming low levels of sodium (Na+; 50 mmol/d) with those consuming high levels of sodium (> or =120 mmol/d), in the context of a diet rich in potassium (K+). Sodium supplementation (NaSp) produced the difference in Na+ intake. Subjects (n = 108; 64 women, 44 men; 16 on antihypertensive therapy) had a mean age of 47.0 +/- 10.1 y. Subjects were given dietary advice to achieve a low sodium (LS) diet with high potassium intake (50 mmol Na+/d, >80 mmol K+/d) and were allocated to NaSp (120 mmol Na+/d) or placebo treatment for 4 wk before crossover. The LS diet decreased urinary Na+ from baseline, 138.7 +/- 5.3 mmol/d to 57.8 +/- 3.8 mmol/d (P < 0.001). The NaSp treatment returned urinary Na+ to baseline levels 142.4 +/- 3.7 mmol/d. Urinary K+ increased from baseline, 78.6 +/- 2.3 to 86.6 +/- 2.1 mmol/d with the LS diet and to 87.1 +/- 2.1 mmol/d with NaSp treatment (P < 0.001). The LS diet reduced home systolic blood pressure (SBP) by 2.5 +/- 0.8 mm Hg (P = 0.004), compared with the NaSp treatment. Hence, reducing Na+ intake from 140 to 60 mmol/d significantly decreased home SBP in subjects dwelling in a community setting who consumed a self-selected K+-rich diet, and this dietary modification could assist in lowering blood pressure in the general population.

Effect of longer-term modest salt reduction on blood pressure

BACKGROUND

Many randomised trials assessing the effect of salt reduction on blood pressure show reduction in blood pressure in individuals with high blood pressure. However, there is controversy about the magnitude and the clinical significance of the fall in blood pressure in individuals with normal blood pressure. Several meta-analyses of randomised salt reduction trials have been published in the last few years. However, most of these included trials of very short duration (e.g. 5 days) and included trials with salt loading followed by salt deprivation (e.g. from 20 to 1 g/day) over only a few days. These short-term experiments are not appropriate to inform public health policy which is for a modest reduction in salt intake over a prolonged period of time. A meta-analysis by Hooper et al is an important attempt to look at whether advice to achieve a long-term salt reduction (i.e. more than 6 months) in randomised trials causes a fall in blood pressure. However, most trials included in this meta-analysis achieved a small reduction in salt intake; on average, salt intake was reduced by 2 g/day. It is, therefore, not surprising that this analysis showed a small fall in blood pressure, and that a dose-response to salt reduction was not demonstrable.

OBJECTIVES

To assess the effect of the currently recommended modest reduction in salt intake (WHO 2003; SACN 2003; Whelton 2002), on blood pressure in individuals with normal and elevated blood pressure. To assess whether the magnitude of the reduction in blood pressure is dependent on the magnitude of the reduction in salt intake.

SEARCH STRATEGY

We searched MEDLINE, EMBASE, Cochrane library, CINAHL, and reference list of original and review articles.

SELECTION CRITERIA

We included randomised trials with a modest reduction in salt intake and a duration of 4 or more weeks.

DATA COLLECTION AND ANALYSIS

Data were extracted independently by two persons. Mean effect sizes were calculated using both fixed and random effect models using Review Manager 4.2.1 software. Weighted linear regression was used to examine the relationship between the change in urinary sodium and the change in blood pressure. We used funnel plots to detect publication and other biases in the meta-analysis.

MAIN RESULTS

Seventeen trials in individuals with elevated blood pressure (n=734) and 11 trials in individuals with normal blood pressure (n=2220) were included. In individuals with elevated blood pressure the median reduction in 24-h urinary sodium excretion was 78 mmol (4.6 g/day of salt), the mean reduction in systolic blood pressure was -4.97 mmHg (95%CI:-5.76 to -4.18), and the mean reduction in diastolic blood pressure was -2.74 mmHg (95% CI:-3.22 to -2.26). In individuals with normal blood pressure the median reduction in 24-h urinary sodium excretion was 74 mmol (4.4 g/day of salt), the mean reduction in systolic blood pressure was -2.03 mmHg (95% CI: -2.56 to -1.50) mmHg, and the mean reduction in diastolic blood pressure was -0.99 mmHg (-1.40 to -0.57). Weighted linear regression analyses showed a correlation between the reduction in urinary sodium and the reduction in blood pressure.

REVIEWERS' CONCLUSIONS

Our meta-analysis demonstrates that a modest reduction in salt intake for a duration of 4 or more weeks has a significant and, from a population viewpoint, important effect on blood pressure in both individuals with normal and elevated blood pressure. These results support other evidence suggesting that a modest and long-term reduction in population salt intake could reduce strokes, heart attacks, and heart failure. Furthermore, our meta-analysis demonstrates a correlation between the magnitude of salt reduction and the magnitude of blood pressure reduction. Within the daily intake range of 3 to 12 g/day, the lower the salt intake achieved, the lower the blood pressure.

Primary prevention of essential hypertension

The best approach to the primary prevention of hypertension is a combination of lifestyle changes: weight loss in overweight persons; increased physical activity; moderation of alcohol intake; and consumption of a diet that is higher in fruits, vegetables, and low-fat dairy products and lower in sodium content than the average American diet (Table 3). Recent randomized controlled trials have demonstrated that these lifestyle changes can be sustained over long periods of time (more than 3 years) and can have blood pressure-lowering effects as large as those seen in drug studies. Hypertension is an important preventable risk factor for cardiovascular disease, the leading cause of mortality in the United States. To achieve the Healthy People 2010 goal of reducing the proportion of adults with hypertension from 28% to 16%, concerted efforts must be directed toward primary prevention strategies. Lifestyle modifications including weight loss, increased physical activity, and dietary changes in individuals have been shown to reduce the incidence of hypertension and should be recommended for all persons and especially those with prehypertension. In addition, timely adoption of prevention strategies to reduce the incidence of hypertension and its subsequent complications in the general population may interrupt the costly cycle of hypertension and prevent the reductions in quality of life associated with this chronic disease.

How far should salt intake be reduced?

The current public health recommendations are to reduce salt intake from 9 to 12 g/d to 5 to 6 g/d. However, these values are based on what is feasible rather than the maximum effect of salt reduction. In a meta-analysis of longer-term trials, we looked at the dose response between salt reduction and fall in blood pressure and compared this with 2 well-controlled studies of 3 different salt intakes. All 3 studies demonstrated a consistent dose response to salt reduction within the range of 12 to 3 g/d. A reduction of 3 g/d predicts a fall in blood pressure of 3.6 to 5.6/1.9 to 3.2 mm Hg (systolic/diastolic) in hypertensives and 1.8 to 3.5/0.8 to 1.8 mm Hg in normotensives. The effect would be doubled with a 6 g/d reduction and tripled with a 9 g/d reduction. A conservative estimate indicates that a reduction of 3 g/d would reduce strokes by 13% and ischemic heart disease (IHD) by 10%. The effects would be almost doubled with a 6 g/d reduction and tripled with a 9 g/d reduction. Reducing salt intake by 9 g/d (eg, from 12 to 3 g/d) would reduce strokes by approximately one third and IHD by one quarter, and this would prevent approximately 20 500 stroke deaths and 31 400 IHD deaths a year in the United Kingdom. The current recommendations to reduce salt intake from 9 to 12 g/d to 5 to 6 g/d will have a major effect on blood pressure and cardiovascular disease but are not ideal. A further reduction to 3 g/d will have a much greater effect and should now become the long-term target for population salt intake worldwide.

A population-based dietary intervention trial in a high-risk area for stomach cancer and stroke: changes in intakes and related biomarkers

BACKGROUND

Dietary intervention is one of the important fields in cancer and cardiovascular disease prevention. The Hiraka Dietary Intervention Study is a community-based randomized cross-over trial designed to develop an effective dietary modification tool and system in an area with high mortality of stomach cancer and stroke.

METHODS

The subjects were 550 healthy volunteers and were randomized into two groups with tailored dietary education to decrease sodium intake and to increase vitamin C and carotene intakes either in the first year (intervention group) or in the second year (control group). Dietary changes were assessed using a validated self-administered diet history questionnaire, fasting blood samples, and 48-hour urine samples, which were obtained before and after the one year period.

RESULTS

During the first year, changes differed significantly between the intervention and control group for both dietary sodium intake (-384 and +255 mg/day, intervention and control respectively, p < 0.001) and urinary sodium excretion (-1003 and -84 mg/day, p < 0.001). Although favorable net changes were also observed in dietary carotene (+418 and +220 mug/day, p < 0.05) and vitamin C (+13 and +2 mg/day, p < 0.05), the serum level differences were modest (+13 and -25 mg/L, p = 0.09 for carotene, +0.1 and -0.5 mg/L, p = 0.07 for ascorbic acid).

CONCLUSION

The present dietary intervention strategy effectively decreased sodium and increased carotene and vitamin C intakes, although the former was more distinct.

Blood pressure response to changes in sodium and potassium intake: a metaregression analysis of randomised trials

The objective of the study was to assess the blood pressure response to changes in sodium and potassium intake and examine effect modification by age, gender, blood pressure, body weight and habitual sodium and potassium intake. Randomised trials of sodium reduction or potassium supplementation and blood pressure were identified through reference lists of systematic reviews and an additional MEDLINE search (January 1995-March 2001). A total of 40 sodium trials and 27 potassium trials in adults with a minimum duration of 2 weeks were selected for analysis. Data on changes in electrolyte intake and blood pressure during intervention were collected, as well as data on mean age, gender, body weight, initial electrolyte intake and initial blood pressure of the trial populations. Blood pressure effects of changes in electrolyte intake were assessed by weighted metaregression analysis, overall and in strata of trial population characteristics. Analyses were repeated with adjustment for potential confounders. Sodium reduction (median: -77 mmol/24 h) was associated with a change of -2.54 mmHg (95% CI: -3.16, -1.92) in systolic blood pressure and -1.96 mmHg (-2.41, -1.51) in diastolic blood pressure. Corresponding values for increased potassium intake (median: 44 mmol/24 h) were -2.42 mmHg (-3.75, -1.08) and -1.57 mmHg (-2.65, -0.50). Blood pressure response was larger in hypertensives than normotensives, both for sodium (systolic: -5.24 vs -1.26 mmHg, P < 0.001; diastolic: -3.69 vs -1.14 mmHg, P < 0.001) and potassium (systolic: -3.51 vs -0.97 mmHg, P=0.089; diastolic: -2.51 vs -0.34 mmHg, P=0.074). In conclusion, reduced intake of sodium and increased intake of potassium could make an important contribution to the prevention of hypertension, especially in populations with elevated blood pressure.

Salt, blood pressure and the renin-angiotensin system

Much evidence from epidemiological, migration, intervention, animal and genetic studies suggests that salt intake plays an important role in regulating blood pressure (BP). At the same time, many clinical trials have shown that reducing salt intake lowers BP. However, the magnitude of the fall in BP for a given reduction in salt intake varies with age, ethnic group and BP levels. This difference has been suggested to be related to the responsiveness of the renin-angiotensin system (RAS). However, the sympathetic nervous system, the kallikrein-kinin system, the nitric oxide system, and many eicosanoids may also play a role. In this article, we address the important role of the RAS in determining the fall in BP with salt reduction.