Dietary Sodium Reduction Research Articles

Managing the whole patient with hypertension: Practical applications in a clinical setting

Physicians are aware of the value of treating hypertension. Complications such as stroke and congestive heart failure are less likely to occur in the well-controlled patient. In our quest to add coronary heart disease to this list, we must go beyond simple reduction of blood pressure. We must consider other risk factors such as hypercholesterolemia, cigarette smoking, diabetes mellitus, and family history. The presence of one or more of these may indicate a more aggressive treatment approach. Similarly the presence of left ventricular hypertrophy, coronary disease, or renal disease may indicate specific pharmacotherapy. On the other hand, the low-risk patient with no other problems or conditions may be treated with only nonpharmacologic therapy such as weight loss, dietary sodium reduction, and/or alcohol restriction. Every patient has a different constellation of findings. Every patient should be treated individually. It is no longer sufficient just to lower blood pressure; we need to manage the whole patient with hypertension; keeping in mind that most antihypertensive agents are equally effective, the side effect profile is often the decisive factor in choosing an antihypertensive agent.

The effect of a household partner and home urine monitoring on adherence to a sodium restricted diet

To evaluate the effects of social support and home urine monitoring on success with dietary sodium reduction, 114 essential hypertensive adults and a household partner were recruited. One of the pair was required to be the food preparer. Patients with their partners were randomly assigned to either an active or passive partner condition. During dietary counseling in the active condition, both patients and partner were involved in instructions to change their diet to reduce their daily sodium intake to 80 mmol or less. In the passive condition, the partners were present during the dietary counseling, but no effort was made to involve them directly in the instruction or to encourage them to make personal dietary changes. Patients and active partners collected two 24-hr urine collections between each of the first two counseling sessions and received feedback on the sodium results by a telephone call. In the passive partner condition, only patients collected urine for feedback. At the end of the 6 week instructional period, all patients and partners collected a 24-hr urine and had their blood pressure assessed. Half of each group was also randomly assigned to have access to a system for periodic home-monitoring of urine for sodium content during a 3-month period beginning at week 6 of the study (immediate). The delayed feedback group received the home-monitoring system three months after completion of the dietary instruction. All patients, but only active partners, used the feedback system during their assignment periods and collected a 24-hr urine monthly between 6 and 30 weeks of the study. Passive partners did not receive feedback on their urinary sodium excretion and collected a 24-hr urine only at weeks 6, 18 and 30. Neither the feedback system not the instructional participation status of the partner made a significant difference in dietary compliance. After dietary instruction, all groups significantly ( P < 0.01) reduced their sodium intake for the duration of the study from baseline values. Regression was observed between 6 and 18 weeks, but at 30 weeks sodium excretion still remained significantly less ( P < 0.05) than baseline. The sodium content of patients' and partners' urines were significantly correlated before and during the study ( r = 0.25-0.37; P < 0.02), independent of their experimental condition. The dietary instruction was able to produce changes in eating habits irrespective of the active participation of the partner in the instructional process. Early provision of self-informed feedback monitoring did not appear to enhance adherence. Individuals most likely to comply were lower-weight females, white or those who had a lower sodium intake at baseline. This study shows that inclusion of the food preparer in face-to-face dietary instruction and telephone feedback on urine results was sufficient to produce reduction in sodium intake and help many sustain that reduction for the duration of the study.

Behavioral aspects of intervention strategies to reduce dietary sodium.

This article addresses general and specific aspects of dietary sodium interventions from the perspective of behavioral change. Changing dietary behavior requires relearning a range of habitual behaviors involved in day-to-day eating situations in the context of a diverse and complex food supply and in consideration of numerous factors, other than health concerns, that influence habitual eating patterns. Potential obstacles to dietary sodium reduction relate to the wide distribution of sodium in foods, the strong cultural values for salt, and the difficulty of assessing success in sodium reduction. A review of sodium interventions reported in the literature suggests that state-of-the-art behavioral change strategies can be effective in achieving reductions in sodium intake to around 3,000 mg/day but that this level is achieved only with highly motivated individuals and when a high level of intervention (i.e., intensive and multifaceted) is provided. Thus, in regard to sodium reduction in the general population, either the goal will have to be modest or the food supply will have to change so that substantial decreases in sodium intake can be accomplished with less intensive and less costly interventions.

Dietary sodium reduction for hypertension prevention and treatment.

Nutritional-nonpharmacological approaches for the treatment and prevention of hypertension are of great interest. Sodium reduction is one of the primary methods recommended for these purposes. The general public is interested in the reduction of dietary sodium intake and has responded with a decrease in table salt use, the purchase of lowered sodium food products, and the use of food labels to help guide food purchases. Countervailing trends in the use of convenience foods and dining out increase the difficulty for individuals to lower sodium intake. Clinical trials that have used sodium reduction alone or in combination with other lifestyle therapies have demonstrated the feasibility of reducing dietary sodium intake from 30% to 50% for up to 4 years, in a variety of populations. Trials that used lifestyle and weight loss interventions have also achieved significant reductions in body weight and alcohol consumption and increases in physical activity. A variety of studies indicate that long-term sodium reduction is feasible and that it is acceptable to patients. No negative consequences of these interventions have been observed, and in some cases improvement in the intake of other nutrients has occurred. Nonpharmacological interventions have resulted in hypertension control in significant proportions of the trial populations. These studies demonstrate that the foregoing types of interventions can significantly contribute to hypertension treatment and prevention.

Discretionary salt and compliance with reduced sodium diet

The present study was designed to quantify dietary sodium sources and to monitor compliance with a diet reduced in sodium by proscriptions in table salt alone (group 1) or all discretionary salt (group 2). Individuals receiving no dietary intervention served as controls (group 3). Following a 3-week baseline period, diets were prescribed for 23 weeks, during which intake was measured by multiple 7-day diet records, weight salt shakers and 24h-urinary collections. Sensory tests were administered to track shifts in salt preference. The principle findings were that 1) discretionary salt contributed little (<10%) to total sodium intake, 2) total discretionary salt use was stable and precisely defended when the table source was eliminated, and 3) reduced exposure to the salty taste elicited a persistent reduced preference for an array of salty foods. These findings suggest that advice to restrict discretionary salt use to achieve a reduction in salt intake may be ineffectual and possibly counter-productive.

Risks Associated With Dietary Sodium Reduction in the Spontaneous Hypertensive Rat Model of Hypertension

Sodium balance is maintained by a complex set up of hemodynamic, hormonal and neural mechanisms that affect intake, reabsorption and excretion. The focus of the following research was on the cardiovascular and neuroeffector effects of dietary Na reduction primarily in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR) raised from 4 to 15 weeks on a control Na diet (CNa: 12 mmol per 100 g food) or various low Na diets (LNa: 0.5 to 3 mmol per 100 g food). With regards to hemodynamics and volume regulation, the lowest Na diet reduced blood pressure 15% and raised resting heart rate (20%) in SHRs but not WKYs. Blood volume, hematocrit, plasma electrolytes, extracellular volume, and cardiac output were not different between diets or strains. However, both LNa strains were abnormally sensitive to blood loss and showed attenuated pressor responses to both acute and chronic stress situations. Cardiac function was not altered by LNa treatment in either rat strain although structural compensations occurred. LNa treatment significantly attenuated the pressor reduction in mesenteric blood flow during stress which was primarily due to reduction in noradrenergic transmitter release and not due to altered receptor sensitivity, density, or Na/K ATPase activity. Compensatory sympathetic activity was increased as was sodium conservation through humoral mechanisms which maintained homeostasis. However, further neurohumoral compensation was markedly reduced. The data suggests that the hygienic sodium intake in humans should be experimentally defined before generalized measures are taken to reduced dietary sodium use throughout society.

Predictive and Preventive Pathology of Cardiovascular Diseases

The development of genetic models for research on hypertension and stroke, spontaneously hypertensive rats (SHR) and stroke-prone SHR (SHRSP), have contributed not only to the elucidation of the pathogenesis of hypertension-related cardiovascular diseases (CVD) but also to their prediction and prevention. Since both genetic and environmental factors are involved in the pathogenesis of hypertension and stroke in SHR and SHRSP, the detection of the genetic factors and the control of environmental factors have been proven to be useful as predictive and preventive measures against hypertension and related CVD. Early rise in blood pressure, sympathetic overresponsiveness, early development of cardiovascular hypertrophy, increased salt-sensitivity and membrane abnormalities detected in vascular smooth muscle cells (VSMC) from SHR and SHRSP, which are related to the pathogenesis of hypertension, have been examined for their applicability to the prediction of hypertension in man. Pathogenic mechanisms of stroke in SHRSP have been studied by electron microscopy, and VSMC degeneration and necrosis were noted to start at the outer media of intracerebral arteries which were exposed to local hypoxia and hyponutrition due to limited diffusion through the blood-brain barrier. Macrophages are involved in the process of arterionecrosis with fibrin deposition in SHRSP, and their involvement has also been proven immunohistochemically in human autopsy cases. Moreover, reduction of regional cerebral blood flow, hypoxic vulnerability of the brain detected by the NMR technique and additional cellular abnormalities such as membrane fragility and accelerated lipid incorporation may possibly be applied to the prediction of stroke and atherosclerotic diseases in man. On the other hand, experimental control of cellular, neural and vascular mechanisms of hypertension and stroke in these animal models have been proven to be effective for the prevention of CVD not only pharmacologically but also non-pharmacologically by dietary sodium reduction, and increased intake of potassium, calcium, protein and dietary fiber. The applicability of dietary control of hypertension and stroke to humans has been supported by our epidemiological studies in Japan as well as by the WHO-coordinated international cooperative study on cardiovascular diseases and alimentary comparison (WHO CARDIAC study). These new experimental and epidemiological findings are extending new horizons in medicine, where the main medical activity should be focused on the prediction of diseases by detecting genetic disposition as well as on prevention by the control of environmental factors.

Failure to Compensate Decreased Dietary Sodium With Increased Table Salt Usage

This study tested the extent to which individuals placed on a lowered sodium diet would compensate for the reduced dietary sodium by adding table salt to their food. Eleven students, unaware that their use of saltshakers was being studied, consumed all their meals and snacks in a clinical research center for 13 weeks. During the first three weeks and the last week (week 14), the diet contained approximately 135 mmol/d (135 mEq/24 h) of sodium, which was reduced to approximately 70 mmol/d (70 mEq/24 h) during weeks 4 through 13. A preweighed saltshaker was available for use throughout the entire 14-week period. Evaluations of salt taste preference and intensity scaling were conducted at regular intervals. Subjects compensated only slightly for the reduction of dietary sodium, making up less than 20% of the decrement with increased saltshaker usage. No changes in taste function were found. A substantial reduction in dietary sodium is possible if lowered-sodium foods are consumed in conjunction with ad libitum table salt.

Sources of sodium, potassium, and energy in the diets of adolescents

Analysis of food diaries of 200 students in two boarding high schools indicated that 30% of their average daily sodium intake was contributed by bakery foods and ready-to-eat cereals. The next most important source of sodium (24%) was a category made up of food adjuncts, snack-type foods, soups, and beverages. The largest proportion of sodium in most foods had been added during food manufacture or preparation. Salt added at the table contributed less than 1% of the sodium in the diets of the teenagers. All students did not eat foods from all categories on their day of recording; 70% or more ate bakery products, dairy foods, food adjuncts, and meat, fish, poultry, and eggs. Changes in recipe formulations can decrease sodium content for a variety of bakery products, cereals, mixed dishes, snack-type foods, soups, and processed meats. It is therefore possible to make large reductions in dietary sodium without disturbing other nutrient values.

Dietary sodium deprivation raises blood pressure in the rat but does not produce irreversible hyperaldosteronism.

It is reported that dietary deprivation of sodium in young rats produces changes of sodium balance and aldosterone excretion which persist when normal sodium intake is restored. To test this further, sodium intake was reduced 10-fold in rats. In the first experiment sodium intake was reduced for 5 weeks in rats aged 3 weeks. Systolic blood pressure, heart rate and plasma renin concentration increased and growth rate was reduced. Sodium intake was then increased for 10 weeks. Blood pressure, heart rate and plasma renin concentration fell and growth rate increased but body weight did not regain control values. As compared with controls, plasma concentrations of aldosterone and corticosterone did not increase after the 10-week period. Thus, sodium depletion did not produce an irreversible change in aldosterone but it did raise arterial pressure. Further experiments confirmed the pressor effect in young and adult rats. Blood pressure was measured in the tail in these experiments but the increase in pressure was not a technical artifact as measurements made in the tail correlated well with measurements made simultaneously by intra-arterial catheter. Catheters were inserted under general anaesthetic for this comparison of pressure and rats previously deprived of sodium showed a significantly higher mortality rate due to the anaesthesia and surgery involved. Thus, a 10-fold reduction of dietary sodium raises blood pressure in young and adult rats and it may increase mortality from a minor surgical procedure. It does not produce irreversible changes in aldosterone.

Effects of a mild and prolonged restriction in sodium or food intake on the circadian rhythm of aldosterone and related variables.

The effect of a mild reduction in dietary sodium intake (-30 mEq/24 hr) and body weight (-2 kg/2 months) on circadian rhythms of urinary aldosterone (UA), sodium (UNa), potassium (UK), creatinine (UC) and volume (UV) have been investigated in nine clinically healthy subjects. The mild reduction in dietary sodium is associated with: (1) a decrease in the 24-hr excretion rate of UNa, UK and UV, and an increased mesor of UA and UC; (2) a lowered extent of the circadian variation for UNa, UK, UV and a greater amplitude for UA and UC (3) a later crest in the temporal phase for UK, UA, UC, an earlier phasic wave for UNa. The mild reduction in calorie intake resulting in a body weight loss is associated with a more pronounced decrease in the 24-hr excretion rate of UNa and UK, and in the extent of circadian fluctuation for UNa. Peculiar events are: (1) the decreased 24-hr excretion rate for UA, and the increased mesor for UV; (2) the extent variability increased for UV, decreased for UC. Such effect may have a practical resonance for heuristic physiology since the role of dietary sodium and food intake has been better clarified. Dietary sodium and food can be regarded as 'chronomodulatory agents' for the adrenal cortex since their adrenotropic influence is extended to the tonic as well as phasic secretion of aldosterone.

Hypertension and nutrition in the young: early intervention?

The few studies, carried out on infants, children, and adolescents, relating blood pressure to sodium intake have shown a weak positive correlation in some but not all individuals. The effect of body size on blood pressure confounds the interpretation of the effect of dietary sodium on blood pressure. There appear to be sodium-sensitive and sodium-unsensitive infants, children, and adolescents and is probably genetically transmitted. Most infants, children, and adolescents in industrialized populations have a salt intake far greater than required, and reduction in dietary sodium is safe and may be beneficial to those individuals with a family history of primary hypertension.

The influence of moderate reduction in dietary sodium on human salivary sodium concentration

Twenty-four healthy subjects were placed for 12–13 weeks on diets that reduced average sodium intake from 145 to 74 m-equiv. Na +/day as determined by multiple 24-h urine collections before and during the diet. Whole-mouth resting and stimulated saliva was collected and analysed for flow rate and sodium concentration several times before and during the low-sodium period. Sodium restriction did not influence salivary flow rates but salivary sodium levels fell 25 per cent for resting and 17 per cent for stimulated saliva. Thus moderate reductions in sodium intake are accompanied by significantly lower salivary sodium levels.

Increasing dietary salt alters salt taste preference

In previous studies with humans, moderate reduction of dietary sodium decreased preference for salty foods. It had been hypothesized that this occurred via reducing taste stimulation with salty foods. Taste function after increasing dietary salt (NaCl), either with or without increasing salt taste stimulation, was examined in two experiments. In Experiment 1, one group of subjects was required to add crystalline salt to food daily for 4 weeks. A second group ingested salt tablets for the same period. A third group ingested a placebo. Whereas urinary sodium excretion increased in both groups ingesting supplemental salt, the concentration of salt in soup rated as tasting most pleasant increased only in the group adding salt to food. Rated intensity of salt did not change. In Experiment 2, salt supplementation was extended to 6 weeks and taste function was tested more extensively. At the end of the experiment, the concentration of salt in soup rated as tasting most pleasant increased in the group which added the crystalline salt to food. This group also added more salt to soup to taste than did the salt tablet group. The most pleasant concentration of KCl in soup was not significantly affected. Taken together these two experiments suggest that the preferred concentration of salt in soup can be increased after dietary salt supplementation and that increased salt taste stimulation is probably required for this to occur.

Moderate dietary salt reduction and salt taste perception of normotensive individuals with family history of hypertension

The purpose of this study is to examine any effects of dietary salt reduction possibly achieved by normotensive, non-institutionalized individuals with a family history of hypertension. Twelve subjects (7 males and 5 females) between 18 and 24 years of age were instructed to follow a reduced sodium diet for 10 weeks. The following data on salt taste perception and physical characteristics were collected during the pre-diet period, during the sixth week of the reduced sodium diet, and during its tenth week. u • taste tests of salt water, broth, and rice, rating salt intensity and preference • body weight • blood pressure • 24-hour urinary sodium, potassium, calcium, and creatinine • whole saliva sodium, potassium, and calcium • 3-day dietary surveys of sodium, potassium, calcium, and caloric intake The data were analyzed using analyses of variance and covariance, and graphical displays. No significant trial effect was found for any response except systolic blood pressure and salivary calcium; the means of these decreased linearly throughout the study. Subjects with high pre-diet calcium (urinary, salivary, and dietary) and high urinary potassium tended to perceive greater saltiness and prefer less saltiness than subjects with low baseline levels.

Dietary sodium reduction among students: Feasibility and acceptance

Modifications in the preparation of food served in a boarding high school during a 5-week period were successful in decreasing the sodium content of a variety of food products by an average of 51%. Such food was, in general, well accepted. The ratings of specific reduced-sodium food products equaled those of similar products containing "usual" amounts of sodium. Food diaries kept by students gave estimates of total sodium intake comparable with those measured by laboratory analysis of 24-hour food collections. Food diaries collected from an average of 70 volunteers per week indicated that during the reduced-sodium period, the total sodium intake of students, including that from dining hall food, snack food, and food consumed outside the school, decreased from 136 mEq (3 gm sodium, 8 gm salt) to 88 mEq (2 gm sodium, 5 gm salt), a reduction of 35% (p less than .0001). The impact of salt added at the table was very small; the choice and the quantity of foods consumed were the main determinants of sodium intake. The results indicate that foods can be prepared with appreciably less sodium and still be highly acceptable to young people.

Achieving Compliance to a Reduced Sodium Diet

Hypertension affects at least 40 million people in the United States today. Nonpharmacological treatment of hypertension relies on modifications in the diet and lifestyle. In refractory cases, the initiation of drug treatment is necessary. Although dietary sodium restriction is widely advocated, assessment of compliance to a reduced sodium diet has been difficult. This article discusses the use of a urinary chloride titrator stick to enable patients to monitor their dietary sodium intake at home. This tool increased compliance to a low sodium diet in the test population.

The effect of sodium intake on the blood pressure related to age and sex.

Two hundred and one volunteers with no known hypertension and 60 patients with untreated hypertension were entered into a study that compared the effect of two levels of sodium intake on blood pressure. One hundred and fifty-four volunteers and 46 hypertensive patients reached compliance goals, with a urinary sodium excretion on the high sodium diet twice that on the reduced sodium intake. The blood pressure on the high sodium diet was 4.5 +/- 0.5 mmHg (n = 154 p less than 0.001) higher than on the reduced sodium diet in normotensive individuals and was increased by 8.4 +/- 1.5 mmHg (n = 46 p less than 0.001) in hypertensive individuals. In the volunteer group the major rise in blood pressure occurred in people over the age of 50. In the hypertensive patients the alteration in blood pressure was not age dependent. In the younger age groups some individuals had an increase in blood pressure when on the high sodium intake which was outside the spontaneous variations in blood pressure of a control group. This implied that a number of young normotensive individuals were susceptible to this alteration in sodium intake. Changes in sodium intake alter blood pressure in hypertensive people, in normotensive people over 50 and in a small number of younger normotensive people. Overall reduction of sodium intake from 200 - 70 mmol/day would reduce the blood pressure level of the population and would reduce the number of people who have a blood pressure that requires drug therapy.

Long-term reduction in dietary sodium alters the taste of salt

A group of young adult subjects was placed on self-maintained, low sodium diets for 5 months. Taste responses to salt in solutions, soups, and crackers were determined both during the 2 months preceding diet initiation and during a 5-month period when subjects lowered their sodium intake. Taste responses were also determined in a control group with ad libitum salt consumption throughout the same period. Perceived intensity of salt in crackers increased. The salt concentrations of maximum pleasantness in soup and crackers fell in the experimental subjects but not in the control subjects. These results demonstrate that the preferred level of salt in food is dependent on the level of salt consumed and that this preferred level can be lowered after a reduction in sodium intake. The implications of these findings for the maintenance of low sodium diets are discussed.

Improving hypertension control in a private medical practice

Hypertension is one of the most common diseases seen by the practicing physician. Yet, because of noncompliance, conditions of many hypertensive patients are not effectively controlled by treatment. The purpose of this study was to test the efficacy of a patient education program in reducing the blood pressure (BP) of hypertensive patients in a private, solo medical practice. The intervention program focused on three behavioral objectives-pill taking, appointment keeping, and dietary sodium reduction while stressing the need for taking responsibility for one's own care. It was hypothesized that patients receiving an educational intervention stressing self-care would benefit more than those receiving the usual medical care. A substantial reduction in BP was considered to be the measure of successful treatment. Thirty-nine hypertensive patients receiving drug therapy from a private, solo medical practice were randomized into either a treatment group or a control group. A comparison of means disclosed no pretreatment differences between the groups' average BPs. After following up both groups for six months, mean changes in BP were compared for both treatment and control patients using a two-sample t test for independent samples. The BP fell in the treatment group (-13 mm Hg, systolic; -8 mm Hg, diastolic) but rose slightly in the control group (3 mm Hg, systolic 0.5 mm Hg, diastolic). The difference in changes was significant for both the systolic and diastolic BP.