High sodium-low potassium environment and hypertension

Sodium chloride preference and recognition threshold in normotensive subjects on high and low salt diet

Young adult volunteers were placed on two week periods of high and low-salt diets following dietetic counselling and using normally available foodstuffs. Changes in sodium recognition threshold, salivary and urinary electrolytes and preference for NaCl, NaCl/KCl (1:1) mix and monosodium glutamate were measured during the high- and low-salt diet periods and during two-week control periods with subjects on their usual diet. Sodium preference was defined as the sodium concentration of unsalted tomato juice following ad libitum addition of a sodium salt till the most preferred taste was achieved. Subjects served as their own controls across the dietary periods in a cross-over design. While sodium excretion on the low-salt diet was significantly less than at on the high-salt diet, there were no significant changes in blood pressure, sodium recognition threshold, body weight or salivary electrolytes between these dietary periods. There was a significant increase in preference for NaCl, NaCl/KCl mix and monosodium glutamate on the high-salt diet when compared to the low-salt diet period. In all dietary periods less sodium was added to the unsalted tomato juice with monosodium glutamate than with NaCl/KCl and less sodium was added with the NaCl/KCl mix than with the NaCl. This study demonstrates that relatively short periods of increased sodium intake result in an increase in sodium preference in the absence of changes in salivary electrolytes or recognition threshold.

Blood pressure and associated factors in a rural Kenyan community

Blood pressure (BP) and associated factors were determined in 1737 men in a remote Kenyan agricultural community. Systolic BP showed no significant rise with age until after 54 years; diastolic BP showed a small rise with age. Both systolic and diastolic BP correlated with weight independent of age. Systolic and diastolic BP correlated positively with casual urinary sodium/potassium and negatively with potassium/creatinine ratios. Both systolic and diastolic BP correlated significantly with the number of years of education, as did urinary sodium/potassium and sodium/creatinine ratios. Potassium/creatinine ratios were negatively correlated with the number of years of education. Blood pressure and urinary sodium/creatinine ratios were significantly lower in subsistence farmers compared with those in other occupations, and potassium/creatinine ratios were significantly higher. Two pilot studies of Luo tribesmen showed a strong correlation between casual urinary electrolyte ratios and those derived from 24-hour urine samples and a greater variance of sodium excretion between these people than that found within individuals. These results suggest that a relationship between BP and casual urine electrolyte estimations may be identifiable in communities where there is less day-to-day dietary variation. They also suggest that some of the changes in BP associated with urbanization could be mediated by changes in dietary electrolytes.

Interrelationships between blood pressure, sodium, potassium, serum cholesterol, and protein intake in Japanese

Interrelationships among blood pressure (BP), sodium (Na), potassium (K), dietary protein, and serum cholesterol level (Chol) were examined in 62% (1120) of 1818 Japanese inhabitants of both sexes aged over 30 years who lived in a rural village in Japan. Fasting single-spot urine specimens were collected in the morning to measure Na, K, urea nitrogen (UN), inorganic sulfate (SO4), and creatinine (Cr). The Cr ratios of Na, K, UN, SO4, Na/K, and SO4/UN were analyzed by multiple regression analysis to determine independent associations with BP together with age, obesity index, hematocrit (Hct), Chol, triglyceride (TG), and fasting serum glucose level (Glu). Except for Na/Cr in men, Na/Cr and Na/K were found to be independently and positively related to BP, particularly to systolic BP (SBP). In contrast, K/Cr and SO4/UN (an index related to the dietary score of sulphur-containing amino acids derived mainly from animal protein) were both negatively associated with SBP, and UN/Cr (an index of total protein intake) was positively associated with SBP in men. Chol was linked to BP negatively in men but positively in women. Age, obesity index, TG, and Hct were generally positively and significantly related to BP in both sexes. The results confirmed on epidemiological grounds the positive link of Na and the negative link of K to BP within a single population in Japan. They further suggest, although only in men, that there is a negative relationship of Chol and dietary animal protein with BP.

Blood pressure and its correlates in an African tribe in urban and rural environments

As part of a longitudinal study of migrants who move from a subsistence farming rural society to Nairobi, blood pressures and associated factors were measured in cross sectional studies of members of the Luo tribe in their traditional rural environment and in the urban environment of Nairobi. Blood pressures in Nairobi correlated with duration of urban residence. In the rural area men showed a negligible rise in blood pressure with age, and both sexes showed a significantly smaller rise than in the urban area. Although mean weights of the rural group were smaller, this did not account for all the urban/rural differences in blood pressures. Nevertheless, mean urinary sodium concentration and sodium ratios (sodium/potassium and sodium/creatinine) were significantly higher in the urban group whereas mean urinary potassium concentration and potassium/creatinine ratio were significantly lower. Perhaps the ratio of sodium to potassium in the diet contributes to the different blood pressure profiles of these two populations.

Preference and sensitivity to salt taste as determinants of salt-intake

Total salt-intake was estimated in 33 normal subjects using urinary sodium excretion over 7 days, and table and cooking salt use were measured over the same period. Sensitivity to salt taste was measured for 31 of these subjects using a seven-category rating scale for intensity of saltiness with five concentrations of salt in water, bread and mashed potato. Preferences were assessed using a nine-category hedonic rating scale with the bread and mashed potato to determine the maximally-preferred concentration. No differences were found in the taste measures between subjects divided into high and low intake in terms of total salt-intake or total intake divided by body weight. However, differences were found in sensitivity and preferences between groups divided into high and low table salt use. This may be because the major proportion of total salt-intake arose from salt present in foods and this would not be so open to voluntary control as table salt use.

Sodium detection threshold and preference for sodium chloride in humans on high and low sodium diets

Sodium detection threshold and preference for sodium chloride was examined in human volunteers on 2 week periods of high and low salt diets. There was no significant difference in salivary electrolytes or sodium detection threshold between the high and low salt diet periods. Sodium preference, defined as the final sodium concentration of unsalted tomato juice following the ad libitum addition of NaCl, was significantly less on the low salt diet when compared to the high salt period. These results suggest that short periods of dietary salt modification can result in marked shifts in preference for NaCl in the absence of changes in the physiological parameters measured.

The effects of familial relationships, age, body weight, and diet on blood pressure and the 24 hour urinary excretion of sodium, potassium, and creatinine in men, women, and children of randomly selected families

Two hundred thirty-three randomly selected families provided a population for studying the effects of familial relationships, age, diet, body weight, and urinary electrolyte excretion on blood pressure. There was a strong familial component for urinary sodium, potassium, and creatinine excretion and for systolic blood pressure. In individuals, age, heart rate, and body weight were independently related to blood pressure. In women, urinary sodium and potassium levels were related to diastolic blood pressure. These individual relationships persisted when age was accounted for but were no longer significant after adjusting for both age and body weight, suggesting that heavier people eat more food, which in our culture means greater sodium intake. In fact, our randomly selected families were eating as much sodium (130 to 170 meq/day) and as little potassium (50 to 70 meq/day) as consumed by Americans several decades ago. Furthermore, this study again documented the rise in blood pressure with age, which may represent the effect of environmental influences on blood pressure over time. The familial aggregation of urinary sodium, potassium, and creatinine excretion, along with the well-established familial aggregation of body weight, emphasizes the importance of the entire family in the treatment and prevention of hypertension.

Low-sodium, high-potassium diet: feasibility and acceptability in a normotensive population

Sixty-nine normotensive volunteers participated in an eight-week study to test the feasibility and acceptability of two low-sodium (less than 70 mEq), high-potassium (greater than 100 mEq) diets. The diet groups differed only in the use of KCl salt substitute. Both dietary groups were able to reduce sodium and increase potassium intake compared to the control group. Urine sodium excretion decreased in the diet groups but no change was observed in potassium. Potassium chloride salt substitute was not used as recommended, suggesting its unacceptability.

Hormonal and nutritional enhancement of Na+-K+-ATPase activity may aid the prevention and treatment of essential hypertension

Subnormal activity of the Na+-K+-ATPase appears to be a common feature of essential hypertension, and may in fact play a pathogenic role in this disorder. If so, methods which relieve inhibition or enhance the activity of the sodium pump should have therapeutic or preventive value. Diuretics enhance the activity of the sodium pump in hypertensives, apparently by suppressing secretion of an inhibitory natriuretic factor, and it is likely that low-sodium diets have a similar effect. Activity of the Na+-K+-ATPase is also stimulated by thyroid hormone and insulin, and there are indications that thyroid therapy, as well as various measures which increase tissue insulin sensitivity, may have therapeutic value in essential hypertension. Nutritional measures which may enhance sodium pump activity include potassium supplementation, insurance of adequate magnesium intake, and consumption of rich sources of gamma-linolenic acid.

Hemodynamic and endocrine changes associated with potassium supplementation in sodium-loaded hypertensives

To clarify the mechanism by which potassium (KCl) protects against the blood pressure rising action of sodium (NaCl), we studied the effects of KCl loading in patients with idiopathic hypertension who, after a period of NaCl restriction, partook of a high NaCl diet. Eleven patients who had taken the KCl supplement (96 mEq/day) during the high NaCl period showed lesser mean blood pressure (MAP) rise with changes in NaCl intake from 25 to 250 mEq/day than 12 patients who had not taken the KCl supplement (p less than 0.001). With a high NaCl diet, the KCl-supplemented patients retained less NaCl, gained less weight, and showed a lesser increase in plasma volume and cardiac output than the non-KCl-supplemented ones. Overall, the increase in blood pressure levels during the high Na diet correlated directly either with changes in plasma volume (p less than 0.05) or with changes in cardiac output (p less than 0.01). The results suggest that KCl may prevent a rise in blood pressure with NaCl loads in hypertensive patients by attenuating the increase in cardiac output, mainly as a result of the natriuresis. Furthermore, plasma norepinephrine was measured to estimate the sympathetic activity, since the sympathetic nervous system is known to control urinary NaCl excretion. From the low NaCl diet to Day 3 of the high NaCl diet, plasma norepinephrine was significantly (p less than 0.01) decreased in the KCl-supplemented patients, whereas it remained unchanged in the non-KCl-supplemented ones.(ABSTRACT TRUNCATED AT 250 WORDS)

Sodium susceptibility and potassium effects in young patients with borderline hypertension

To evaluate sodium susceptibility in subjects with borderline hypertension at increased risk of developing essential hypertension, the effect of salt loading after sodium deprivation with a diuretic was studied in 21 young patients with borderline hypertension and 12 age-matched normal subjects. Treatment with a diuretic caused significant decreases in mean blood pressure (MBP) in subjects with borderline hypertension but not in normotensive subjects. In borderline hypertensives, the subsequent sodium loads resulted in a significant rise in MBP (5.8 +/- 1.7%; p less than .01), but sodium did not change MBP in normotensives. There is a good correlation between the increments in MBP with sodium loads and the decrements in MBP with a diuretic for each patient (r = -.759, p less than .001). After diuretics, cardiac index (CI) as measured echocardiographically fell significantly but calculated total peripheral resistance (TPR) remained unchanged in subjects with borderline hypertension. After 180 meq sodium chloride each day was added for 7 days, CI (9.1 +/- 2.1%; p less than .01) and stroke index (21.0 +/- 3.4%; p less than .01) rose significantly but TPR remained unchanged. Overall, the increments of MBP with sodium loads did not correlate with the changes in CI but did correlate with the changes in TPR (r = .567, p less than .01). In these young patients with borderline hypertension, plasma norepinephrine and epinephrine concentrations and plasma renin activity (PRA) were significantly higher than in normotensive subjects.(ABSTRACT TRUNCATED AT 250 WORDS)

Low-sodium diet versus low-sodium/high-potassium diet for treatment of hypertension

In 21 patients with essential hypertension the effects of moderate sodium restriction from the usual 200 mmol Na/day to 80 mmol/day over 4 weeks were compared with the effects of a combined low-sodium/high-potassium intake (80 mmol Na/120 mmol K) which was also given over 4 weeks in an open crossover trial. Systolic blood pressure in nine untreated patients with essential hypertension decreased significantly by between 5 and 7 mm Hg during moderate sodium restriction; no further decrease of blood pressure occurred during the combined low-sodium/high-potassium diet. In 12 treated patients with essential hypertension moderate sodium restriction or the combined low-sodium/high-potassium diet enabled a marked reduction of anti-hypertensive therapy in eight patients without impairment of blood pressure control (beta-blockers by an average of 32%, saluretics by an average of 27% and vasodilators by an average of 24%). Here there were also no substantial differences between low-sodium intake and the combined low-sodium/high-potassium intake. It is concluded that sodium restriction to 80 mmol/day is effective in lowering systolic blood pressure but that a combined low-sodium/high-potassium diet does not further improve blood pressure control if the usual potassium intake is at least 80 mmol/day. Considerable reduction of anti-hypertensive therapy may be achieved by practical moderate sodium restriction.

Effects of gene-environment interactions on cardiovascular risk factors in Chinese adolescent twins

A population-based sample of 73 male and 77 female monozygotic (MZ), and 41 male and 33 female dizygotic (DZ) Chinese adolescent twin pairs were studied to assess effects of gene-environment interactions of systolic blood pressure (SBP), diastolic blood pressure (DBP), serum cholesterol and triglyceride levels. Intrapair concordance in BP levels was found to be significantly associated with the interaction of zygosity and salty foods preference and also with that of zygosity and vegetable preference. A consistently positive and statistically significant association was observed between the intrapair difference in serum cholesterol and the interaction of zygosity and animal organ preference; while intrapair concordance in serum cholesterol was associated with the interaction of zygosity and milk consumption. Intrapair difference in serum triglycerides was associated with the interaction of zygosity and fish preference, and a significant association was also found between the intrapair concordance in serum triglycerides and the interaction of zygosity and sweets preference. These observations suggest that the impact of these environmental agents may be influenced by the genotype.

Prevention of age-associated loss of autonomy: epidemiological approaches

The concept of autonomy is proposed as a global objective of health and social services and epidemiological contributions to devising procedures for maintaining autonomy of old people are reviewed. It is suggested that the conventional model of "normal" vs "pathological" aging, identification of the "elderly" as a separate adult age group and preoccupation with clinical as opposed to public health models of intervention and with service provision rather than with clients' needs are less than optimal. More attention should also be given to the identification of extrinsic factors in aging and to recognising ways in which the effects of aging are aggravated by social conditions and unrelieved by ineffectual and inappropriate services. Epidemiology has more to contribute to meeting the challenges of aging than is generally recognised.

Environmental effects on cardiovascular risk factors in Chinese adolescent monozygotic twins

The monozygotic (MZ) cotwin control method was employed to elucidate possible environmental determinants of systolic blood pressure (SBP), diastolic blood pressure (DBP), serum cholesterol and triglyceride levels. A population-based twin sample of 73 male and 77 females MZ twin pairs was recruited from 12 junior high schools in Taipei city. Intrapair differences in blood pressure were negatively associated with intrapair difference in vegetable preference, attaining significance for DBP in males and SBP in females. Cholesterol was positively associated with milk consumption and preference for sweets, fried foods, meat and fish. A negative association was also observed between cholesterol and vegetable preference. These associations for cholesterol were significant in males only. Triglyceride level negatively associated with preferences for sweets and vegetable, attaining significance for vegetables in both males and females and for sweets in males only.

Natriuretic and antihypertensive effects of potassium in DOCA-salt hypertensive rats

The role of a natriuresis in the protective effect of potassium against the development and maintenance of salt-induced hypertension was studied. Uninephrectomized rats showed average systolic pressures of 177 +/- 3 mm Hg after the 28 days of treatment with DOCA while receiving a 1% NaCl solution to drink. The supplements of 0.2 and 1% KCl solution could counteract the blood-pressure raising effect of NaCl in a dose-related fashion: The average pressures on day 28 at these dosages were 131 +/- 3 and 120 +/- 3 mm Hg, respectively. The cumulative sodium retention was significantly less in the KCl-supplemented rats than the DOCA-salt rats. Exchangeable body sodium (sodium "space") at weeks 1 and 4 was significantly increased in the DOCA-salt rats as compared to those in the vehicle-treated rats. But, the potassium supplement could reduce sodium "space" dose-relatedly in the DOCA-salt rats. Overall, there was a close correlation between the systolic pressures and sodium "space" at week 4 (r = 0.811, P less than 0.01). The results suggest that potassium may attenuate the rise in blood pressure during the DOCA-salt treatment in uninephrectomized rats, mainly as a result of inhibition of sodium retention, by increasing renal sodium excretion.

Role of dietary potassium in the treatment of hypertension

This review summarizes the historical development and recent resurgence of interest in dietary potassium as a factor in hypertension. Some epidemiologic evidence has suggested that potassium intake by humans may be inversely related to the level of arterial blood pressure. Other studies have suggested that a marked reduction in the Na+/K+ ratio of the human diet reduces the blood pressure of normotensives. Further, the administration of high potassium diets has resulted in a lowering of blood pressure in some animal models of hypertension. Several possible mechanisms for this putative antihypertensive effect are evident. Some observations suggest that potassium could act as a diuretic agent and thereby reduce extracellular fluid volume, which in turn could result in decreased blood pressure. An alternative mechanism of action is that potassium may alter the activity of the renin-angiotensin system and reduce angiotensin influences on vascular, adrenal, or renal receptors. Other evidence supports the possibility that potassium modifies central or the peripheral neural mechanisms that regulate blood pressure. In addition, high potassium diets could reduce blood pressure by relaxing vascular smooth muscle and reducing peripheral vascular resistance directly. Although diets high in potassium content do appear to modify arterial blood pressure under some circumstances, particularly in salt-dependent hypertension, a high potassium intake has not always attenuated blood pressure in all models examined. Further, evaluation of these data do not allow definite conclusions regarding a common mechanism through which potassium exerts these effects.

Sodium and potassium intake and blood pressure

There is increasing circumstantial evidence that the very high sodium diet combined with low potassium intake that most Western communities now eat may be, at least in part, responsible for the prevalence of high blood pressure. This circumstantial evidence combined with animal evidence has been considered sufficient in some countries to make a general recommendation to reduce sodium intake. If high sodium intake is an important cause of high blood pressure, it is not clear at the present time how it may do so. In this report, evidence is reviewed for one hypothesis suggesting an inherited defect in the kidney's ability to excrete sodium in patients who are going to develop essential hypertension, together with evidence for a raised concentration of an inhibitor of sodium transport. In patients with established hypertension, moderate restriction of sodium intake appears to lower blood pressure and moderate potassium supplementation to also lower blood pressure. While further evidence is required, particularly long-term studies, it would seem prudent to recommend to patients with essential hypertension or a strong family history of hypertension that they restrict dietary sodium intake moderately and increase dietary potassium intake by the consumption of more fruits and vegetables and, perhaps, the use of a potassium-based salt substitute. This regimen could obviate or reduce the need for drug treatment in some patients with mild to moderate hypertension.

Influence of carboxyhemoglobin, gamma-glutamyl-transferase, body weight, and heart rate on blood pressure in middle-aged men

Carboxyhemoglobin (COHb%) and gamma-glutamyl-transferase (GGT) are indicators of tobacco and alcohol consumption; similarly, body weight broadly reflects dietary habits. Relationships between COHb%, GGT, relative body weight, heart rate and blood pressure were studied in 242 48-year-old men attending a general health screening program in Malmö, Sweden. All were without treatment for high blood pressure. Positive correlations were found between blood pressure and body weight, GGT, and pulse, and a reciprocal correlation between blood pressure and COHb%. Use of objective markers for known or suspected risk factors, such as alcohol consumption, smoking, or overweight, were studied to elucidate their usefulness for further prospective studies.

Effect of magnesium on blood pressure

Twenty patients receiving long term diuretic treatment for arterial hypertension (18 patients) or congestive heart failure (two patients) received magnesium supplementation as aspartate hydrochloride 15 mmol/day for six months. Both systolic and diastolic pressures decreased significantly, by a mean of 12/8 mm Hg. No significant changes were recorded in plasma or urinary electrolytes except for magnesium, 24 hour urinary volumes, or body weight after treatment. The effect of magnesium on blood pressure may be direct or through influences on the internal balance of potassium, sodium, and calcium.

Potassium load in spontaneously hypertensive rats. Effects on blood pressure, renin-angiotensin, aldosterone, and intracellular electrolytes

To study the mechanisms by which K+ influences vascular tone in hypertension, spontaneously hypertensive and normotensive rats were examined during an oral K+ load. There was a marked decrease in blood pressure in spontaneously hypertensive but not in normotensive rats. Intraerythrocytic K+ concentration and activity increased in normotensive but not in spontaneously hypertensive rats. Intraerythrocytic Na+ concentration and activity declined in both strains, the decrease in Na+ activity being more prominent in spontaneously hypertensive rats (P less than 0.05). Intraerythrocytic Ca2+ activity decreased in spontaneously hypertensive rats (P less than 0.01) but not in normotensive rats. In both strains plasma aldosterone concentration increased during K+ load, the plasma renin activity being suppressed. The basal levels of plasma aldosterone in spontaneously hypertensive rats exceeded those in normotensive rats. It is concluded that intraerythrocytic Ca2+, and to a lesser extent Na+, correlate best with the blood pressure changes. These ionic changes may be mediated by hormonal factors. The significance of the elevated plasma aldosterone levels has not yet been entirely clarified.

Failure of captopril to lower blood pressure in spontaneously hypertensive rats offered water and saline to drink

The hypotensive action of chronic oral captopril treatment (50 mg/kg per day) was examined in two groups of male spontaneously hypertensive rats (SHR) of the Okamoto strain, one group offered a choice of water and 0.9% saline as drinking fluid, the other offered water alone, a third group of SHR, offered a choice of water and 0.9% saline, were treated with vehicle (0.9% saline, 2 ml/kg per day). Captopril treatment, over ten days, significantly lowered blood pressure in the group drinking water only but failed to significantly alter the blood pressure of SHR drinking a choice of water and 0.9% saline. Vehicle treatment did not alter the blood pressure of SHR drinking a choice of saline and water. In an identical experiment using male, genetically hypertensive rats (GHR) of the Smirk strain, captopril lowered blood pressure to the same extent in GHR drinking either a choice of water and 0.9% saline or water alone. In conclusion, the reported exaggerated saline preference of the spontaneously hypertensive rat appears to antagonize the hypotensive action of captopril.

Dietary sodium and potassium-induced transient changes in blood pressure and catecholamine excretion in the Sprague-Dawley rat

When Sprague-Dawley derived rats were changed from a chow type diet to a moderately high sodium diet, rapid transient changes in blood pressure (BP) and catecholamine excretion were observed. After 1 dietary week, BP increased from 122 +/- .1 mm Hg to approximately 145 mm Hg (p less than 0.001), and there was a concomitant 20% reduction in urinary norepinephrine (UNEV) and epinephrine (UEV) excretion (p less than 0.05). Heart rates were reduced (p less than 0.05). These data suggest that sodium-induced increases in BP were initially associated with suppressed sympathetic nervous system activity. During dietary Weeks 2 and 3, some animals had a persistent moderate elevation in BP (BP less than or equal to 150 mm Hg), while others developed more severe increases. UNEV in moderately hypertensive animals returned to control levels during this period; but UEV and heart rates remained suppressed. UNEV in severely hypertensive animals exceeded (13% +/- 3%, p less than 0.05) that of controls. This increase coincided with their most severe hypertension (171 +/- 1 mm Hg, p less than 0.001). UE values and heart rate data indicate that systemic adrenergic tone was likely suppressed at this time and that the increased UNEV was renal in origin. By dietary Week 4, the BP of severely hypertensive animals had begun to fall, and indices of sympathetic nervous system tone were indistinguishable among all groups. Inclusion of a dietary potassium supplement ameliorated the development of hypertension only in those animals that became severely hypertensive, and appeared to prevent the early suppression of indices of sympathetic activity.

Refined carbohydrates - a cause of suboptimal nutrient intake

During the refining of carbohydrate foods there is a sharp drop in the concentration of dietary fiber and of various vitamins and minerals. Estimates were made of the effect of refining on the total diet intake of fiber, selenium, folic acid, vitamins E and B6, choline, chromium, magnesium, zinc, manganese, copper, sodium and potassium. The health implications of this are discussed and it is concluded that the losses are likely to be detrimental.

Relation between ingested potassium and sodium balance in young Blacks and whites

The relationship of dietary K+ with Na+ balance in young normotensives was studied. A, In two biracial communities, all children with specified age were stratified by blood pressure level. Children from selected strata collected 24-h urines on ambulatory basis and provided fasting blood for electrolytes and creatinine determination. For the upper percentile ranks (n = 160), the Na+ and K+ clearances correlated closer in Blacks than whites (r = 0.7 versus r = 0.4, p less than 0.005 for difference). B, To test for a causal effect of K+ intake on Na+ excretion, six white and eight Black young healthy normotensive volunteers took 80 mEq KCl daily in addition to their usual diets. They collected 24-h ambulatory urine and stool samples for 3 base-line days, and 4 days during K+ supplementation. Na+ and K+ intake was monitored daily. Upon K+ supplementation, Blacks showed natriuresis (p less than 0.01), negative Na+ balance (p less than 0.05), and a cumulative K+ balance more positive than whites (p less than 0.0001 versus p less than 0.05). Dietary K+ enrichment could affect Na+ balance.

Relation of blood pressure to reported intake of salt, saturated fats, and alcohol in healthy middle-aged population

The association of blood pressure with reported intake of salt, saturated fats, and alcohol was studied in a sample of 8479 subjects based on a cross sectional survey in a population aged 30 to 64 years. A consistent association was found between the mean arterial pressure and the intake of alcohol (p less than 0.001) and saturated fats (p less than 0.01). There was also a weak association between blood pressure and dietary salt intake, but this association was mostly explained by the correlation of salt intake with alcohol and saturated fats. The observed relationships support the hypothesis that blood pressure is influenced by diet.

Achievements in hypertension: a 25 year overview

Only 25 years ago, the field of hypertension was challenged by retrospective clinical data and epidemiologic information suggesting that an elevated arterial pressure is a major risk factor for enhanced cardiovascular morbidity and mortality. Not only was antihypertensive therapy looked on by many as dangerous and fraught with severe and undesirable side effects, but its validity in reversing the course of disease was not yet demonstrated. This review discusses the dramatic new information amassed over the past 25 years that points to the new physiologic and clinical concepts concerning hypertension. It considers impressive new diagnostic techniques and methods designed to identify secondary forms of hypertension and target organ involvement. In summary, it outlines the feasibility of reversing overall (and cardiovascular) morbidity and mortality with an array of antihypertensive agents that provide the therapeutic ability to suppress most pathophysiologic pressor mechanisms of hypertensive disease. The lesson is clear: hypertension provides the greatest available challenge to the new era of preventive cardiology in the 21st century.

Randomised double-blind cross-over trial of potassium on blood-pressure in normal subjects

A randomised double-blind cross-over study of increased oral potassium 64 mmol a day versus placebo was conducted in 20 young healthy males on normal sodium unrestricted diet. A significantly greater proportion had lower systolic and diastolic blood-pressures on potassium than on placebo. The mean diastolic pressure was significantly lowered, by 2.4 mm Hg, during potassium supplementation. Change in diastolic pressure correlated negatively with change in 24-hour urinary potassium and positively which change in 24-hour urinary sodium/potassium ratio in individual subjects.

Moderate potassium supplementation in essential hypertension

23 unselected patients with mild to moderate essential hypertension, whose average supine blood pressure after two months' observation on no treatment was 154/99 mm Hg, were entered into an eight week double blind randomised crossover study of one month's treatment with slow release potassium tablets (60 mmol/day) versus placebo without alteration of dietary sodium or potassium intake. By the fourth week mean supine blood pressure had fallen by 4% on potassium supplementation compared with placebo. Urinary potassium excretion increased from 62 +/- 4.7 mmol/24 h on placebo to 118 +/- 7.4 mmol/24 h on potassium. The fall in blood pressure was not related to urinary sodium excretion before entry to the trial or while on placebo. Moderate potassium supplementation caused a small but significant fall in blood pressure in patients with mild to moderate essential hypertension and could be additive to the effects of moderate sodium restriction. This increase in potassium intake could be achieved with a potassium-based salt substitute and a moderate increase in vegetable and fruit consumption. Moderate dietary sodium restriction with dietary potassium supplementation may obviate or reduce the need for drug treatment in some patients with mild to moderate hypertension.

Human nutrition and blood pressure regulation: an integrated approach

This review highlights the complex interactions that constitute the disciplines of nutrition and cardiovascular physiology. Nutritional factors have long been considered as critical in the pathogenesis of human hypertension. Theoretical and established contributions of various nutrients to blood pressure regulation are presented. A brief historical perspective of sodium's dominance in this area is provided. "Accepted" principles of nutrient interaction are then applied to cardiovascular research. First, the interrelationships among all macronutrients and diet composition, nutrient absorption, renal elimination, and ultimate bioavailability to the vascular tissue are assessed. An analysis of dietary recall data from human studies is provided to illustrate such nutrient interaction. Second, associated factors that influence nutrition are considered in relation to both human and animal investigations of blood pressure regulation. Finally, the development and interpretation of future studies are assessed in light of these principles. Examples from both the human and animal investigations of blood pressure regulation. Finally, the development and interpretation of future studies are assessed in light of these principles. Examples from both the human and animal literature are provided to show why it is necessary to incorporate fully the established principles of nutrition into our current concepts of the pathogenesis of hypertension. Future progress in terms of nutrition, food, and health will be dependent upon such an integrated approach.

Dietary calcium in human hypertension

A pilot survey was made of the dietary calcium intake of normotensive and hypertensive individuals. Compared to 44 normotensive controls, 46 subjects with essential hypertension reported significantly less daily calcium ingestion (668 +/- 55 milligrams compared to 886 +/- 89 milligrams). The intake of other nutrients, including sodium and potassium, was very similar in the two groups. The hypertensives differed from the controls primarily in their consumption of nonfluid dairy products. The data suggest that inadequate calcium intake may be a previously unrecognized factor in the development of hypertension.

Studies on high affinity binding of mineralo- and glucocorticoids in rabbit aorta cytosol

High affinity, specific binding-sites to mineralocorticoids and glucocorticoids, with characteristics of steroid receptors, have been found in rabbit aorta cytosol. Binding parameters (dissociation constants and number of binding sites per mg of cytosol protein) were determined from Scatchard plots, after statistical treatment of the data with the aid of a computer program, for the following tritiated steroids: 11-desoxycorticosterone (DOC), aldosterone (Aldo), progesterone (Prog), corticosterone (BK), cortisol (FK) and dexamethasone (Dex). The specificity of binding was then examined by means of steroid competition studies. The results of these experiments indicate that three different types of high-affinity binding sites to adrenal steroids are present in aorta cytosol: Type A, with the highest affinity for DOC; Type B, with the highest affinity for FK; Type C, with the highest affinity for Dex. In accordance with the relative competitive potencies of various steroids for these binding sites, Type A is designated as the "arterial mineralocorticoid binder", clearly differing in its binding characteristics from the cytoplasmic mineralocorticoid binders in known target tissues to these steroids (e.g. the renal receptor), while Type C is designated as the "arterial glucocorticoid binder", closely resembling the classical glucocorticoid receptor in known target tissues to glucocorticoids. Type B exhibited some of the binding characteristics of transcortin and may represent a modified, intracellular transcortin. While Types B and C are present also in the cytosol of inferior vena cava. Type A was only in the aorta. The role of these binders is not known at present. Arguments are presented in favor of a hypothesis that the Type A (mineralocorticoid) binder represents an arterial wall; and that, under certain conditions, this action leads to an increased contractility of arterial and arteriolar smooth muscles, increased peripheral resistance and hypertension.

Abnormal relationship between sodium intake and sympathetic nervous system activity in salt-sensitive patients with essential hypertension

To examine the mechanisms underlying the sensitivity to sodium intake in a subset of patients with essential hypertension, we studied the effects of different sodium intake (10, 100, 200 mEq/day) on blood pressure, the function of the renin-angiotensin-aldosterone system, and on blood levels of catecholamines in 20 patients with essential hypertension and 10 normal subjects. Mean blood pressure (MBP) was not different in hypertensive and normal subjects during low sodium diet. But, with high sodium intake, MBP increased by at least 10% in 12 patients (salt-sensitive), whereas in the remaining 8 patients (salt-resistant) and in normal subjects, MBP did not change significantly. This phenomenon cannot be attributed to differences in sodium retention because the percent change in body weight ad the urinary sodium excretion in the salt-sensitive patients was not different than it was in salt-resistant patients or in normal subjects. The observed difference in blood pressure response to high sodium intake in salt-sensitive patients is also not dependent on an impaired suppressibility of the renin-angiotensin-aldosterone system because there were no significant differences in the basal levels of PRA and aldosterone between the groups, and because the orthostatic increments in PRA were significantly lower in salt sensitive than they were in the salt-resistant patients and in normal subjects. Plasma norepinephrine (NE) levels were not significantly different between normal subjects or hypertensive patients while on low sodium intake. But during high sodium intake, they decreased significantly (P less than 0.05) in normal subjects (from 22 +/- 3.4 to 12 +/- 2.3 ng/dl) and in salt-resistant patients (from 17 +/- 4.5 to 13 +/- 2.4 ng/dl) but not in salt-sensitive patients (from 20 +/- 1.9 to 22 +/- 3.2 ng/dl). Furthermore, the majority of salt-sensitive patients displayed inappropriately high plasma NE in relation to their urine excretion of sodium during high sodium intake. Finally, the increments in plasma NE after 5 min of standing were significantly greater in salt-sensitive patients than they were in salt-resistant patients and normal subjects during both low or high sodium intake. These data indicate that a subset of patients with essential hypertension may have impaired suppressibility of plasma NE during high sodium intake, which suggests hyperactivity of the sympathetic nervous system in these patients. These aberrations may be responsible for the increase in MBP in the salt-sensitive patients during high sodium intake.