The relationship between both sodium and potassium intake and blood pressure in London Civil Servants. A report from the Whitehall Department of Environment Study

Plasma sodium, extracellular fluid volume, and blood pressure in healthy men

In the general population we recently reported a consistent association between plasma sodium and volume markers, suggesting that individuals with higher plasma sodium have higher extracellular fluid volume (ECFV). To test this hypothesis, we analyzed the association between plasma sodium and directly measured ECFV (iothalamate distribution volume) in healthy men. Second, we studied whether plasma sodium is associated with blood pressure. We analyzed data from 70 men (age 24 ± 7 years) at the end of two 7-day periods on a low-sodium diet (LS, 50 mmol Na/24 h) and a high-sodium diet (HS, 200 mmol Na/24 h), respectively. The association of plasma sodium with blood pressure was assessed in the combined data of the different sodium intakes by linear mixed effects models. A positive univariable association between plasma sodium and ECFV was found during HS (β = 0.24, p = 0.042) and LS (β = 0.23, p = 0.058), respectively. Individual values of plasma sodium on LS and HS diet were strongly correlated (β = 0.68, p < 0.001), as were values for ECFV (β = 0.54, p < 0.001). In the combined data set plasma sodium level was significantly associated with ECFV (B [SE] = 0.10 [0.04], p = 0.02), and systolic blood pressure (SBP, B [SE] = 0.73 [0.26], p = 0.006), independent of ECFV. In conclusion, plasma sodium concentration is positively associated with ECFV on both LS and HS intake. Our data confirm and extend prior data on individual regulation of plasma sodium and suggest that this is associated with individuality of the regulation of ECFV. Finally, plasma sodium level is associated with SBP, independent of ECFV and diet.

Association between urinary potassium excretion and blood pressure: A systematic review and meta-analysis of observational studies

Background

The evidence base regarding the association between urinary potassium and blood pressure (BP), or risk of hypertension, is inconsistent. Therefore, we sought to conduct a qualitative and quantitative literature review on the association between potassium excretion and BP.

Materials and Methods

Medline, Scopus, Web of Science, Science Direct, and Google Scholar were searched up to June 2020. All observational studies that reported BP and measured potassium excretion in overnight or 24-h urine samples were included. Correlation coefficients, mean urinary potassium excretion, and odds ratio (ORs) of hypertension were extracted from the included studies. There were no language or publication date restrictions.

Results

Overall, twelve observational studies, including 16,174 subjects, were identified for inclusion in the present meta-analysis, and 21 effect sizes were extracted. Pooled mean potassium excretion was 3.46 mmol/24 h higher in normotensive individuals compared with hypertensive subjects (95% confidence interval [CI]: 0.61, 6.31). High urinary potassium excretion was not associated with the risk of hypertension (OR: 0.95; 95% CI: 0.79, 1.13). The pooled correlation coefficient between BP and urinary potassium was not significant (ES: 0.01; 95% CI: -0.03, 0.05). However, a subgroup analysis by age indicated a significant positive correlation between urinary potassium and systolic BP in children (ES: 0.12; 95% CI: 0.04, 0.19).

Conclusion

24 h urinary potassium excretion was not correlated to BP and risk of hypertension. In contrast, mean urinary potassium excretion was higher in normotensive individuals compared with hypertensive counterparts. Future studies should focus on the association between different sources of dietary potassium and BP.

Clinical and neurohumoral associates of variations in plasma Na+in the PREVEND cohort

Plasma Na+concentration is regulated within narrow limits. Yet, substantial interindividual differences exist even in the normal range. The determinants of these differences are not well understood. We therefore investigated the clinical and neurohumoral associates of plasma Na+. We studied 2,364 men (age: 48 ± 12 yr) and 2,710 women (age: 47 ± 12 yr) from the prospective Prevention of Renal and Vascular End-Stage Disease (PREVEND) cohort study. In the present study, we investigated the neurohumoral factors NH2-terminal prohormone of brain natriuretic peptide (NT-proBNP) and aldosterone as volume markers and copeptin as a marker for osmoregulation. Clinical associating variables of plasma Na+were age, sex, and plasma glucose. Furthermore, plasma Na+levels were associated with log2copeptin (men: standardized β = 0.18, P < 0.001; women: standardized β = 0.17, P < 0.001), log2NT-proBNP (men: standardized β = 0.07, P = 0.008; women: standardized β = 0.12, P < 0.001), and log2aldosterone (men: standardized β = −0.06, P = 0.005; women: standardized β = −0.09, P < 0.001). Copeptin and NT-proBNP showed an interaction in their association with plasma Na+. Thus, our data 1) support that osmoregulation, as estimated from copeptin levels, is a main associate of plasma Na+; 2) show a consistent association with volume markers, with higher NT-proBNP and lower aldosterone in individuals with higher plasma Na+; and 3) show that the interaction between copeptin and NT-proBNP illustrates that osmoregulation and volume regulation act in concert in the regulation of plasma Na+.

Nutritional profiles in a public health perspective: a critical review

Nutritional profiling is defined as 'the science of categorizing foods according to their nutritional composition' and it is useful for food labelling and regulation of health claims. The evidence for the link between nutrients and health outcomes was reviewed. A reduced salt intake reduces blood pressure, but only a few randomized controlled trials have verified the effect of salt on overall and cardiovascular mortality. Evidence linking a reduced fat intake with cardiovascular mortality and obesity is generally non-significant. Studies that have examined the relationship between obesity and diet have produced contrasting results. A simulation exercise that demonstrated that the impact of a reduced salt and fat intake on overall mortality would be negligible in the European population was carried out. Consideration of the literature and the results of this simulation exercise suggest that the introduction of nutritional profiles in Europe would be expected to have a very limited impact on health outcomes.

Interindividual variation in serum sodium and longitudinal blood pressure tracking in the Framingham Heart Study

BACKGROUND

Recent cross-sectional studies have suggested that higher serum sodium levels may be a marker of elevated blood pressure. It is unclear whether serum sodium levels are related to the risk of developing hypertension in the community.

METHODS

We investigated the association of serum sodium with longitudinal blood pressure tracking and incidence of hypertension in 2172 nonhypertensive Framingham Offspring Study participants (mean age 42 years, 54% women). We defined an increase in blood pressure as an increment of at least one category (as defined by the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure), and incident hypertension as a systolic blood pressure of at least 140 or a diastolic blood pressure of at least 90 mmHg, or use of antihypertensive medications. Serum sodium was analyzed as a continuous variable, and as categories.

RESULTS

Cross-sectionally, serum sodium was not associated with systolic or diastolic blood pressure (P exceeded 0.10). On follow-up (mean 4.4 years), 805 participants (37%, 418 women) progressed by at least one blood pressure category, and 318 (15%, 155 women) developed new-onset hypertension. In multivariable logistic regression analyses (adjusting for age, sex, baseline blood pressure, diabetes, BMI, weight gain and smoking), serum sodium was not associated with blood pressure progression (odds ratio per SD increment 0.93, 95% confidence interval 0.85-1.03), or with hypertension incidence (odds ratio per SD increment 0.94, 95% confidence interval 0.82-1.08).

CONCLUSION

In our large community-based sample, serum sodium was not associated with blood pressure cross-sectionally, or with blood pressure tracking or hypertension incidence longitudinally.

Salt and hypertension: a phylogenetic perspective

Our hunter-gatherer ancestors appeared to survive on little salt. When today's rural dwellers move to urban environments, they increase their salt intake and the salt-sensitive among them become prone to age-related increase in blood pressure and hypertension. This paper reviews our knowledge of the mechanisms of salt disposal and plasma volume regulation, salt consumption in human evolution, salt intake and prevalence of hypertension, and the results of interventions aimed at modulating both. Finally, it discusses current hypotheses on the mechanisms of selective pressure that may have favored the emergence of a salt-sensitive, hypertensive genotype. Similar to 'thrifty' genes, which supported energy savers in times of scarcity, but may now be causing obesity and type 2 diabetes, 'thirsty' genes, by acting on salt and water retention, might have helped individuals survive the challenge of volume-depleting illnesses, especially when combined with stress-inducing situations, but may now cause high BP and related damage in the post-reproductive age.

Why do some people look older than they should?

BACKGROUND

As a component of studies on biological age, the age of subjects from their appearance (perceived age) was estimated.

OBJECTIVE

To determine the factors associated with looking older.

METHODS

Cross sectional study of London civil servants (318 men, 129 women) in the Department of the Environment study. Perceived age was recorded by an observer and the difference between this age and chronological age was analysed according to 20 different variables.

RESULTS

Men had an average perceived age of 0.37 years older than their actual age and women a perceived age of 0.54 years younger. In men, looking older was related to greying of the hair, grade of arcus senilis, and grade of baldness. Less expected, looking older was positively related to total serum cholesterol (p=0.03) and blood haemoglobin (p<0.01). In women, looking older was related to greying of the hair, positively to blood erythrocyte sedimentation rate (ESR), and negatively to serum bilirubin (p=0.01). Looking older was not related to alcohol consumption, employment grade, serum high density lipoprotein cholesterol, glucose, albumin, and calcium in either sex.

CONCLUSION

The relationships between looking older and total cholesterol and haemoglobin in men and ESR and bilirubin in women, require further investigation.

Life style as a blood pressure determinant

In Belgium, an affluent Western European country, participation in sports, alcohol intake, and living in a working class area were identified as the life style factors with the closest associations with the blood pressure level. Obesity was another important blood pressure correlate. Sodium intake, determined from the 24 h urinary output, and smoking were not associated with blood pressure. Controlled intervention studies have proven that weight reduction, endurance training and alcohol abstinence effectively reduce blood pressure. In the light of these intervention studies, the Belgian findings and the published work highlight the potential of preventive strategies aimed at these major life style factors.

The relationship between plasma cholesterol concentration and minor psychiatric disturbance in the Department of the Environment Study

We examined the hypothesis that low plasma cholesterol concentration was associated with minor psychiatric disturbance in a cross-sectional study of 410 male and 138 female civil servants. Psychiatric disturbance was measured using the 30-item General Health Questionnaire (GHQ). Mean GHQ score did not vary significantly with quartile of total cholesterol concentration. After adjustment for confounding variables a significant trend of increasing mean GHQ with increasing cholesterol concentration emerged. In a logistic regression analysis subjects in the highest quartile of cholesterol concentration had an adjusted odds ratio for being a "psychiatric case" of 2.0 (95% confidence interval, 1.1-2.5) compared with those in the lowest quartile. This relationship reversed when using a higher cutoff point to define more severe cases, although the trend was not statistically significant.

Age differences in biochemical and hematological measures during middle age

Biochemical and hematological measures possibly associated with ageing were measured on a single occasion in 3402 male and 2152 female London Civil Servants aged from 35 to 59 years of age. These included erythrocyte sedimentation rate (ESR), blood hemoglobin and serum albumin, calcium, bilirubin, creatinine, urea, urate, high density lipoprotein (HDL), and total cholesterol. Independently and positively related to age were ESR with an estimated 47% 'increase' in men over the 15 years between ages 40 to 55 and a 40% increase in women; serum urea had a 6%/15-year increase in men and 20% in women; total cholesterol had a 6%/15-year increase in men and 18% in women; serum creatinine 'increased' by 2%/15-years in men and 5% in women. In women, urate, HDL cholesterol and hemoglobin increased with age group. Negatively related to age was serum bilirubin in both sexes (8% and 6% 'fall'/15-years in men and women respectively). Serum albumin and calcium fell with age group in men. The sexes differed in their relationship to aging for total cholesterol and HDL cholesterol (greater increase in women), serum calcium (small decrease in men and small increase in women), urate and hemoglobin (increases in women but not men). Urea increased more in women than men, and albumin decreased more in men than women (p < 0.001 for all comparisons with the exception of HDL cholesterol, p < 0.01). Changes during the menopause were thought to explain some of these findings.

The assessment of biological age: a report from the Department of Environment Study

Indicators of ageing were measured in 397 male and 130 female London Civil Servants aged from 37 to 58 years of age. Grey hair, skin inelasticity, and arcus senilis were strongly and independently related to chronological age. Also independently related were serum albumin (negatively related in both sexes), baldness, serum creatinine, systolic blood pressure, serum calcium (negatively) and ESR in men, and serum cholesterol in women. Chronological age was regressed on the above variables for men and women separately to provide regression equations. Biological age for an individual was calculated by entering his or her results and calculating the residuals. Biological age in those who stopped smoking tended to be younger than chronological age by an average of 12-13 months in men and 1-4 months in women. Men and women who had never smoked had higher biological than actual ages but not after adjusting for regression dilution bias. Men who currently smoked had higher biological ages of 2-3 months but not women smokers (4-6 months lower). Similarly, men of lower employment grades had an average biological age 13 months older and women 8 months, compared with higher employment grades. These differences between employment grade appeared to be due to ESR, arcus senilis, systolic blood pressure and serum cholesterol. These four measurements may be markers of biological rather than chronological age, and the value of attempting to measure biological age is discussed.

Metal content of drinking water supplied to the city of Maracaibo, Venezuela

Total dissolved aluminum, calcium, iron, potassium, magnesium and sodium were evaluated in the drinking water supplied to the city of Maracaibo, Venezuela, to ascertain the water quality for human consumption. Mean concentrations (+/- S.D.) of 533 +/- 313 micrograms/l Al, 32 +/- 4 mg/l Ca, 167 +/- 104 micrograms/l Fe, 2 +/- 1 mg/l K, 5 +/- 2 +/- 1 mg/l K, 5 +/- 1 mg/l Mg and 16 +/- 4 mg/l Na were obtained during a 4-month sampling period that included dry (January-February 1991) and wet (March-April 1991) seasons. Significant seasonal variations (P < 0.002) for aluminium, potassium and magnesium were as follows: 641 +/- 275 and 445 +/- 340 micrograms/l aluminium, 3 +/- 0.5 and 2 +/- 0.5 mg/l potassium and 4 +/- 0.2 and 6 +/- 2 mg/l magnesium for the wet and dry seasons, respectively. The concentration of aluminum was consistently higher than the levels accepted by most international water quality criteria (approximate acceptable value < 300 micrograms/l aluminum), probably because of the inadequate flocculation treatment given to the raw water at the water plant. The rest of the metals under consideration complied with international guidelines of quality criteria for drinking water. The presence of an elevated concentration of humic material (22 +/- 2 mg/l of total organic carbon) in the drinking water should be a matter of public concern.

Correlates of blood pressure in community-dwelling older adults. The Cardiovascular Health Study. Cardiovascular Health Study (CHS) Collaborative Research Group

Although elevated blood pressure is an important predictor of cardiovascular disease and stroke in the elderly, little information exists on the distribution and risk factor correlates of blood pressure in this group. As part of the Cardiovascular Health Study, a population-based cohort study of 5201 men and women aged 65 to 101 years, we investigated correlates of systolic and diastolic blood pressure. Multiple regression analyses were conducted for all participants and a subgroup of 2482 without coronary heart disease and not on antihypertensive therapy (the "healthier" subgroup). In the total group, independent predictors of diastolic blood pressure included heart rate, aortic root dimension, creatinine, hematocrit, alcohol use, and black race (positive associations) and internal carotid artery wall thickness, mitral early/late peak flow velocity, white blood cell count, cigarette smoking, and age (negative associations). Positive predictors of systolic blood pressure included mitral late peak flow velocity, left ventricular mass, common carotid artery wall thickness, serum albumin, factor VII, diabetes, alcohol use, and age; negative predictors were coronary heart disease, uric acid, height, and smoking. In the healthier subgroup, positive predictors of diastolic blood pressure included heart rate, hematocrit, serum albumin, creatinine, and body weight, whereas mitral early/late peak flow velocity, serum potassium, smoking, and age inversely related to diastolic pressure. For the same group, common carotid artery wall thickness, left ventricular mass, serum albumin, factor VII, high-density lipoprotein cholesterol, and age were directly related to systolic blood pressure, whereas serum potassium was inversely related. Both systolic and diastolic pressures varied considerably by geographic site.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of diet in the genesis and treatment of hypertension

In this brief review, we have not been able to address all of the various dietary factors which have been implicated as causal in hypertension. Because of the heterogeneity of hypertension, it is quite difficult to find a simple answer to the question of how important dietary factors are in causing hypertension and even more difficult to answer the question of how diet should be therapeutically altered in treating a hypertensive patient. Given the difficulties in achieving good compliance to almost any dietary prescription and the lifestyle changes these therapies often require, significant benefit must be demonstrated to justify the efforts. It is worth emphasizing that many of the dietary alterations which have been proposed for treating hypertension have even better established preventative health rationales which justify their use. Although salt intake is a factor in the genesis of hypertension, the effectiveness of salt restriction varies between patients. Despite the absence of good predictors of response, moderate sodium reduction is a reasonable first step when dealing with a hypertensive patient. In obese hypertensive patients, weight loss provides a modest but significant BP reduction. Added benefit may be obtained by lowering total fat content and increasing the ratio of polyunsaturated to saturated fats. The reduction in cardiovascular risk with these changes in dietary fat, over and above the lowering of BP, make this approach appropriate in all hypertensive patients. Potassium supplementation, while sometimes effective, is more difficult to recommend broadly. Calcium supplementation is certainly reasonable in women, for whom such therapy should be seen as good dietary advice for the prevention of osteoporosis. Moderate alcohol intake probably has little deleterious effect, whereas heavy alcoholism does contribute to increased BP. Again, reduction of alcohol intake is important for reasons other than the modest BP reduction attained.

By how much does dietary salt reduction lower blood pressure? II--Analysis of observational data within populations

OBJECTIVE

To determine whether the estimates of the size of the association between blood pressure and sodium intake derived from studies of individuals within populations can be quantitatively reconciled with our estimates derived from comparisons of the average blood pressure and sodium intake between different populations.

DESIGN

Examination of data from 14 published studies that correlated blood pressure recordings in individuals against measurements of their 24 hour sodium intake (within population studies).

MAIN OUTCOME MEASURE

Comparison of observed differences in blood pressure per 100 mmol/24 h difference in sodium intake in each within population study with predicted differences calculated from the between population data, after allowing for the underestimation of the true association of blood pressure with sodium intake caused by the large day to day variation in 24 hour sodium intake within individuals.

RESULTS

The underestimation bias inherent in the within populations studies reduced the regression slope of blood pressure on single measures of 24 hour sodium intake to between a half and a quarter of the true value (for example, in one study from 6.0 to 2.4 mm Hg/100 mmol/24 h). Estimates from between population comparisons of the regression slope of blood pressure on sodium intake, after adjustment to take this underestimation bias into account, were similar to the values actually observed in the within population studies.

CONCLUSION

The within population studies confirm our estimates from between population comparisons of the magnitude of the association between blood pressure and sodium intake.

Relation of electrolytes to blood pressure in men. The Yi people study

The relations of sodium, potassium, calcium, and magnesium to blood pressure were investigated in four groups of men (119 high-mountain Yi farmers, 114 mountainside Yi farmers, 89 Yi migrants, and 97 Han people) with a wide range of electrolyte intake in Puge County, Sichuan Province, People's Republic of China. Electrolytes were measured in diet, serum, and urine. Sodium excretion was 73.9 mmol/24 hr in high-mountain Yi farmers, 117.9 mmol/24 hr in mountainside Yi farmers, 159.4 mmol/24 hr in Yi migrants, and 186.0 mmol/24 hr in the Han people. In ecological correlation analysis, dietary and urinary sodium were significantly and positively correlated with both systolic and diastolic pressure, whereas serum sodium showed no relation with blood pressure. In diet, serum, and urine, potassium was negatively related to systolic and diastolic pressure, whereas the sodium/potassium ratio showed a positive association. With regard to calcium, only urinary excretion was significantly and positively related to blood pressure. No relation was found between magnesium and blood pressure. Analyses at the individual level confirmed the results for sodium and potassium seen at the ecological level, but in addition, dietary calcium and magnesium were significantly and negatively correlated to both systolic and diastolic pressure, and urinary magnesium was inversely related to diastolic pressure. These relations persisted after controlling for age, body mass index (kg/m2), heart rate, alcohol, and total energy intake in multiple regression analysis performed separately for electrolytes in diet, serum, and urine. In multiple regression analysis, an increase in sodium intake of 100 mmol/day corresponded to an increase of 2.3 mm Hg systolic blood pressure and 1/8 mm Hg diastolic pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood lead concentration, renal function, and blood pressure in London civil servants

Blood lead concentration was measured in 398 male and 133 female London civil servants not subject to industrial exposure to heavy metals. The relation between blood lead and serum creatinine concentrations and blood pressure were examined. Blood lead concentration ranged from 0.20 to 1.70 mumol/l with a geometric mean concentrations of 0.58 mumol/l in men and 0.46 mumol/l in women (p less than 0.001). In women blood lead concentration increased with age (r = +0.27; p = 0.002). In the two sexes blood lead concentration was positively correlated with the number of cigarettes smoked a day (men r = +0.17 and women r = +0.22; p less than or equal to 0.01), with the reported number of alcoholic beverages consumed a day (men r = +0.34 and women r = 0.23; p less than 0.01), and with serum gamma-glutamyltranspeptidase (men r = +0.23 and women r = +0.14; for men p less than 0.01). Blood lead concentration was not correlated with body weight, body mass index, and employment grade. In men 14% of the variance of blood lead concentration was explained by the significant and independent contributions of smoking and alcohol intake and in women 16% by age, smoking, and alcohol consumption. In men serum creatinine concentration tended to rise by 0.6 mumol/l (95% confidence interval from -0.2 to +1.36 mumol/l) for each 25% increment in blood lead concentration. In men and women the correlations between blood lead concentration and systolic and diastolic blood did not approach statistical significance. In conclusion, in subjects not exposed to heavy metals at work gender, age, smoking, and alcohol intake are determinants of blood lead concentration. At a low level of exposure, lead accumulation may slightly impair renal function, whereas blood pressure does not seem to be importantly influenced. Alternatively, a slight impairment of renal function may give rise to an increase in blood lead concentration.

The Canadian consensus report on non-pharmacological approaches to the management of high blood pressure

The Canadian Consensus Conference on Non-Pharmacological Approaches to the Management of High Blood Pressure reviewed in March, 1989 on its meeting in Halifax, Nova Scotia, data concerning the efficacy of eight interventional strategies used for controlling hypertension. These strategies were as follows: alcohol restriction, weight reduction, physical exercise, reduction of salt intake, relaxation/stress management, increase of potassium and calcium intake and combination of pharmacological and non-pharmacological management. The Panel of the Consensus Conference recommended as efficacious the following interventions: alcohol restriction for less than two standard drinks per day, reduction of excessive body weight, and reduction of salt intake. There is sufficient scientific evidence for recommending potassium rich diet for normotensives and hypertensive persons. The Panel also concluded that a combination of pharmacological and non-pharmacological management is an efficacious measure. The Panel at this point of time could not issue recommendations as to the value of relaxation/stress management, physical exercise and calcium intake.

Effect of changing dietary sodium on the airway response to histamine

The airway response to histamine has been shown to be related to the 24 hour urinary excretion of sodium. To assess whether this relation is likely to represent a direct causal association a randomised double blind crossover trial of slow sodium (80 mmol/day) was compared with placebo in 36 subjects having a low sodium diet. The dose of histamine causing a 20% fall in FEV1 (PD20) was 1.51 doubling doses lower when the men were taking sodium than when they were taking placebo (p less than 0.05). On the basis of PD10 values, the difference in men was 1.66 doubling doses of histamine (p less than 0.05). There was no corresponding effect in women. Regressing PD10 against urinary excretion of electrolytes with data from the two occasions during the trial and the measurements made before the trial showed a significant association with sodium excretion after allowance had been made for any effect associated with potassium or creatinine excretion, the latter being a marker of the completeness of the urine collection. Again there was no corresponding effect among women. These findings are compatible with the differences in regional mortality data for England and Wales, which show a relation between asthma mortality and regional per person purchases of table salt for men but not for women.

The association between blood pressure, age, and dietary sodium and potassium: a population study

We examined the relationship between blood pressure and dietary sodium and potassium intake estimated from 24 hr diet recall in a population of 584 men and 718 women 30 to 79 years old in Southern California. In men, but not women, age-adjusted systolic and diastolic blood pressure correlated significantly with dietary sodium intake. In both men and women, age-adjusted diastolic blood pressure significantly inversely correlated with dietary potassium intake. Age-adjusted systolic and diastolic blood pressure correlated significantly with the dietary sodium/potassium ratio in each sex; correlations were better for the ratio than for either sodium or potassium alone. The relationship was apparent over the whole range of blood pressure and dietary intake. A marked age gradient was apparent in men, the regression slope for blood pressure vs sodium/potassium ratio increasing with increasing age, suggesting increasing sensitivity to dietary sodium/potassium ratio with age. Adjusting for intake of other dietary variables, including calories, protein, carbohydrate, saturated fat, alcohol, calcium, and fiber, did not alter the relationships; adjusting for body mass index reduced the strength of the association in women but not in men. These results support the hypothesis that dietary sodium and potassium are related to blood pressure within a population.

Urinary and serum electrolytes in untreated black and white hypertensives. Veterans Administration Cooperative Study Group on Antihypertensive Agents

Twenty-four hour urinary excretion of sodium (Na), potassium (K), Na/K ratio and creatinine (Cr), serum Cr, Na, and K, and plasma renin activity (PRA) were evaluated in 623 untreated hypertensive men. Blacks (n = 407) and whites (n = 216) were similar in weight, heart rate, systolic blood pressure (SBP), diastolic blood pressure (DBP), 24-hour urine Cr excretion, and Cr clearance. Twenty-four hour urine Na excretion was the same in blacks and whites, but whites excreted 62% more K than blacks: 73 +/- 41 (mean +/- SD) vs 45 +/- 40 mEq/24h (p less than 0.001). Urinary Na/K ratio was 4.51 +/- 2.18 in blacks and 2.85 +/- 1.40 in whites (p less than 0.001). Serum K and PRA were also lower in blacks. Serum and urine Na/K ratios, serum Na and age were positively associated with SBP; serum K and PRA were negatively associated with SBP. Serum Na/K ratio, heart rate and weight were positively associated with DBP; serum K was weakly negatively associated with DBP. The racial difference in urinary K excretion and serum K is believed to reflect a difference in dietary K intake between blacks and whites. This difference may be an important factor in the greater prevalence of hypertension among blacks.