Simple method for sampling consecutive 24-hour urine for epidemiological and clinical studies

Stroke-Prone SHR as Experimental Models for Cardiovascular Disease Risk Reduction in Humans

Since stroke-prone spontaneously hypertensive rats (SHRSP) develop hypertension and stroke without exception, the prevention or reduction of risk by various nutrients was tested on blood pressure and the mortality caused by stroke and cardiovascular diseases (CVD). In addition to sodium (Na) accelerating hypertension and stroke and potassium (K) counteracting the adverse effect of Na, taurine (Tau), rich in seafood, and magnesium (Mg) contained in soy, nuts, grains, etc., were proven to reduce stroke and CVD and improve survival. Therefore, the Cardiovascular Diseases and Alimentary Comparison Study was started in 1985 to explore the association of biomarkers of diet in 24 h urine (24U) with CVD risks, and about 100 males and 100 females aged 48-56 in each of 50 populations were studied until 1995. Linear regression analysis indicated that the 24U Tau/creatinine and Mg/creatinine ratios were inversely associated with body mass index, systolic and diastolic blood pressure, and total cholesterol. In comparison with six Euro-Western regions, 24U Tau and Mg collected from six regions, respectively, in Japan and the Mediterranean countries were significantly higher and were significantly associated with lower CVD risks. Diets rich in Tau and Mg were concluded to be contributory to the prevention of CVD in SHRSP and humans.

Association between 24 h Urinary Sodium and Potassium Excretion and Dietary Intake in Japanese Male Adolescent Football Players

High urinary sodium-to-potassium ratio is considered a strong risk factor for hypertension. This study aimed to evaluate urinary excretion of sodium and potassium, and we analyzed these levels associated with dietary intake in Japanese adolescent football players. This cross-sectional study included 120 Japanese male adolescent football players. Over 24 h, urine was collected and measured for creatinine, sodium, and potassium levels. A dietary assessment was performed using a self-administered diet history questionnaire. The study analyzed 79 participants. The mean urinary sodium was 143.2 mmol/day, urinary potassium was 42.8 mmol/day, and the mean urinary sodium-to-potassium ratio was 3.6. Compared with the Japanese Dietary Reference Intakes, the estimated salt intake was 73.4% for the participants who exceeded the sodium intake, and the estimated potassium intake was 73.4% for the participants who did not satisfy it. Multiple regression analysis revealed that milk and dairy product intake was independently and positively associated with urinary potassium (β = 0.252) and independently and negatively associated with the urinary sodium-to-potassium ratio (β = −0.254). Adolescent football players had a high-sodium and low-potassium diet, well above the Japanese Dietary Reference Intakes recommendations. Milk and dairy products could be effective for increasing urinary potassium and decreasing the urinary sodium-to-potassium ratio.

Cross-Sectional Inverse Association of Regular Soy Intake with Insulin Resistance in Japanese Elderly

Levels of isoflavones, biomarkers of soy intake, in 24-hour urine (24U) were inversely related to coronary heart disease (CHD) mortality in the World Health Organization's Cardiovascular Disease and Alimentary Comparison Study. Considering 24 U isoflavone levels were highest and CHD mortality was lowest in the Japanese, who maintained the world's longest life expectancy, the association of regular soy intake with cardiometabolic risk was investigated in Japanese adults (20-49 years old) and elderly (50-79 years old). In multivariate analysis adjusted for age, sex, and drug treatments, mean 24 U isoflavone excretion was significantly inversely associated with insulin resistance in the elderly and significantly associated with blood folate and potassium in the elderly, but also positively associated with 24 U salt in the elderly. These findings indicate that low-salt soy should be recommended to improve glucose metabolism in elderly Japanese.

Soy and fish as features of the Japanese diet and cardiovascular disease risks

In the World Health Organization (WHO)-coordinated Cardiovascular Disease and Alimentary Comparison Study, isoflavones (I; biomarker for dietary soy) and taurine (T; biomarker for dietary fish) in 24-hour-urine (24U) were inversely related to coronary heart disease (CHD) mortality. High levels of these biomarkers are found in Japanese people, whose CHD mortality is lowest among developed countries. We analyzed the association of these biomarkers with cardiovascular disease risk in the Japanese to know their health effects within one ethnic population. First, to compare the Japanese intake of I and T with international intakes, the ratios of 24UI and 24UT to creatinine from the WHO Study were divided into quintiles for analysis. The ratio for the Japanese was the highest in the highest quintiles for both I and T, reaching 88.1%, far higher than the average ratio for the Japanese (26.3%) in the total study population. Second, 553 inhabitants of Hyogo Prefecture, Japan, aged 30 to 79 years underwent 24-U collection and blood analyses. The 24UT and 24UI were divided into tertiles and adjusted for age and sex. The highest T tertile, compared with the lowest tertile, showed significantly higher levels of high-density lipoprotein-cholesterol (HDL-C), total cholesterol, 24U sodium (Na) and potassium (K). The highest I tertile showed significantly higher folate, 24UNa and 24UK compared with the lowest tertile. The highest tertile of both T and I showed significantly higher HDL-C, folate, and 24UNa and 24UK compared with the lowest tertile. Thus, greater consumption of fish and soy were significantly associated with higher HDL-C and folate levels, possibly a contributor to Japan having the lowest CHD mortality and longest life expectancy among developed countries. As these intakes were also associated with a high intake of salt, a low-salt intake of fish and soy should be recommended for healthy life expectancy.

Mediating effects of nocturnal blood pressure and morning surge on the contributions of arterial stiffness and sodium intake to morning blood pressure: A path analysis

BACKGROUND

The aim of this study was to evaluate the mediating effects of nocturnal blood pressure (BP) and morning surge on the contribution of arterial stiffness and sodium intake to morning BP in a middle-aged general population.

METHODS

The study included 124 subjects aged 30-59 years, from rural Yeoju County, Gyeonggi Province, South Korea. Ambulatory BP monitoring, 24 h urinary sodium excretion (24 h UNa) and brachial-ankle pulse wave velocity (baPWV) measurements were performed in all subjects.

RESULTS

The mean ± SD age was 48.1 ± 8.2 years and the proportion of male subjects was 41.1%. After adjusting for covariates, morning systolic blood pressure (SBP) was significantly correlated with morning surge [coefficient = 0.761, 95% confidence interval (CI) 0.651-0.872, p < 0.001], nocturnal SBP (coefficient = 0.576, 95% CI 0.454-0.698, p < 0.001) and baPWV (coefficient = 3.550, 95% CI 1.447-5.653, p = 0.001). Path analysis modeling revealed that baPWV had significant direct (0.035, p = 0.013) and indirect effects (0.042, p = 0.012) on morning SBP. The indirect effect mediated by nocturnal SBP was statistically significant (0.054, p = 0.005), but the indirect effect mediated by the morning surge was not significant. The 24 h UNa had no significant direct or indirect effects on morning SBP.

CONCLUSION

baPWV had significant direct and indirect effects on morning SBP. The indirect effect was mediated by nocturnal SBP, but not by morning surge. The 24 h UNa had neither significant direct nor indirect effects on morning SBP.

An inverse association between magnesium in 24-h urine and cardiovascular risk factors in middle-aged subjects in 50 CARDIAC Study populations

Serum, plasma and dietary magnesium (Mg) have been reported to be inversely associated with cardiovascular disease risk factors. We examined the associations between the 24-h urinary Mg/creatinine (Cre) ratio and cardiovascular disease risk factors, such as body mass index (BMI), blood pressure (BP), serum total cholesterol (TC) and prevalence of obesity, hypertension and hypercholesterolemia. A cross-sectional analysis was conducted among 4211 participants (49.7% women) aged 48-56 years in 50 population samples from 22 countries in the World Health Organization-coordinated Cardiovascular Diseases and Alimentary Comparison (CARDIAC) Study (1985-1994). In linear regression analyses, Mg/Cre ratio was inversely associated with BMI, systolic BP (SBP), diastolic BP (DBP) and TC (P for linear trend <0.001 for each). These associations were not markedly altered by adjustment for traditional risk factors, urinary markers or cohort effects. Multivariate-adjusted mean values for the subjects in the highest Mg/Cre ratio quintile were 6.3, 3.4, 5.3 and 4.6% lower than those for the subjects in the lowest quintile for BMI, SBP, DBP and TC (P < 0.001, respectively). The prevalence of obesity, hypertension and hypercholesterolemia was 2.10 (95% confidence interval: 1.50, 2.95), 1.55 (1.25, 1.92) and 2.06 (1.63, 2.62) times higher (P < 0.001, respectively) among the subjects in the lowest Mg/Cre ratio quintile than in the subjects in the highest quintile. These associations were not appreciably altered by adjustment for potential confounding variables. In conclusion, higher 24-h urinary Mg/Cre ratio was associated with lower cardiovascular disease risk factors, including BMI, BP, TC, obesity, hypertension and hypercholesterolemia.

Relationship between nocturnal blood pressure and 24-h urinary sodium excretion in a rural population in Korea

BACKGROUND

The relationship between sodium intake and blood pressure (BP) is affected by many factors such as absolute level of sodium intake, salt sensitivity, and the accuracy or the timing of the BP measurement. There is no epidemiologic study using both ambulatory BP monitoring (ABPM) and 24-h urine sample in a middle-aged general population.

METHODS

In the rural area, Yeojoo County, Gyunggi Province in South Korea, 218 subjects with age between 30 and 59 years old were measured with ABPM and 24-h urine sample. ABPM device was TM2430, and the 24-h urine sample was collected using the aliquot cup. Metabolic syndrome (MetS) score was calculated by the sum of the number of abnormal criteria other than BP.

RESULTS

For both ABPM and 24-h urine sample, 148 subject data was acceptable for the analysis by the creatinine equation and/or the completeness of collection. Age was 47.4 ± 8.3 years (range 30 to 59 years), and female was 85 (57.4%). In multiple linear regression analysis, sodium intake was not an independent factor for casual BPs and daytime BPs whereas sodium intake was an independent factor for nighttime systolic BP (β = 1.625, p = 0.0026) and nighttime diastolic BP (β = 1.066, p = 0.0017). When compared to the lowest quartiles of sodium intake, daytime diastolic BP and nighttime BPs were in the higher three quartile groups.

CONCLUSIONS

Sodium intake was associated not with casual BPs and daytime BPs but with increased nighttime BPs in the middle-aged general population in Korea.

Taurine's health influence on Japanese high school girls

BACKGROUND

The prevalence of metabolic syndrome (MS) in children and adolescents has been increasing at an alarming rate. MS risks during childhood and adolescence adversely affect health conditions in later life. Thus, the characterization of their MS risks is a critical research field. The aims of this study are to survey the health status of Japanese adolescent females, a poorly characterized population, and to investigate the potential relationship between their MS risks and dietary factors like potassium (K) and taurine.

METHODS

Anthropometric characteristics of 243 healthy school girls aged 13 to 18 years were measured. Serum levels of triglycerides, total cholesterol and high-density lipoprotein (HDL), and plasma levels of glucose and insulin were analyzed in fasting blood samples. We assessed overweight, disturbed lipid prolife, higher blood pressure (hBP) and higher plasma glucose (hGlc) levels as indicators of MS risks. The relationships between MS risks and urinary K or taurine excretion were investigated by dividing into higher and lower groups at medians of their urinary excretions.

RESULTS

Half of junior high school (JHS) and one-quarter of senior high school (SHS) girls had at least one MS risk. The quite common risk was hGlc, the rates being 21% in JHS girls and 14% in SHS. The prevalence of being overweight and obesity were only small portions, the rate being 0% and 0% in JHS girls, and 10% and 1% in SHS, respectively. Substantial differences in the prevalence of hBP were observed between JHS (22%) and SHS (4%) girls. Furthermore, higher urinary K excretion group showed a significant decrease in triglyceride level (P = 0.03) and increase in HDL level (P = 0.003) compared with the lower. Also, the higher urinary taurine excretion group exhibited a significant reduction in triglyceride level (P = 0.04) compared with the lower.

CONCLUSIONS

These results indicate that control of plasma glucose level rather than body weight is a crucial task in Japanese pubertal girls, and that a dietary habit rich in K and taurine could improve their lipid profile. Nutritional education based on these findings would help to prevent the future development of MS in Japanese female adolescents.

Deterioration of traditional dietary custom increases the risk of lifestyle-related diseases in young male Africans

Background

Prevalence of metabolic syndrome (MS) is rapidly increasing worldwide. To investigate the spread of MS risks and its relationship with eating habits including fish intake, we carried out a health examination for young and middle-aged men.

Methods

The subjects were 97 healthy men (20 to 50 years) living in Mwanza, located on the shore of Lake Victoria in Tanzania. The health examination was conducted according to the basic protocol of WHO-CARDIAC (Cardiovascular Diseases and Alimentary Comparison) Study. This survey included anthropometric measurements, a dietary questionnaire, blood pressure measurement, and blood and 24-hour urine (24U) collection. Excretions of sodium, potassium and taurine (Tau) in 24U were estimated as the biomarkers of salt, vegetable and fish product intakes respectively.

Results

In this survey, 62.5 % of the young and 63.3% of the middle-aged adults had MS risks. The most prevalent MS risk factor was increased blood pressure (50.0% of young adults and 53.1% of the middle-aged). Tau excretions in 24U and n-3 fatty acid levels in plasma were significantly lower in young adults than those in the middle-aged (both P < 0.05). The eating frequencies of non-traditional foods such as donuts and ice cream showed negative correlations with age (r = -0.282, P < 0.01 and r = -0.246, P < 0.05), while salt intake positively correlated with age (r = 0.236, P < 0.05). Tau excretion in 24U was inversely correlated with atherosclerosis index (r = -0.306, P < 0.01) and fasting blood glucose (r = -0.284, P < 0.05).

Conclusions

Young adults in Mwanza had a decreased frequency of eating habit of fish products compared with the middle-aged as indicated by Tau excretion in 24U and n-3 fatty acid level in the plasma, and over half of young adults had one or more MS risks just as the middle-aged. The change in food habit of lowered fish intake and raised exotic food intake might be concluded to increase MS risks in young men.

Taurine in morning spot urine for the useful assessment of dietary seafood intake in Japanese children and adolescents

Background

Since our previous report on WHO CARDIAC Study data demonstrated that 24-hour urinary (24U) taurine (Tau) excretion was a useful biomarker of seafood (SF) intake and inversely related to the mortality rates of stroke and coronary heart diseases in the world, we determined that SF is important in the risk reduction of lifestyle related-diseases. The amounts of dietary SF intake are so far estimated from a nutritional survey or 24U Tau excretion.

The sodium/potassium ratio of spot urine (SU) and the 24U ratio were reported to be significantly correlated with. Therefore, we presently examined the relationship of Tau excretion in the morning SU with 24U Tau for simplifying the population comparison and the follow-up of SF intake changes in the process of food education program (FEP).

Methods

After informed consent was obtained, 54 children aged 6-11 years (Children) and 193 adolescents aged 13-18 years (Adolescents) participated in collecting precisely 24U and SU of the first urination on the same day and answered the questionnaire including age and height and weight measurements. The urine samples were measured for creatinine (Cre) and Tau, and the association of these between 24U and SU were analyzed.

Results

The success rates of 24U sampling were very high in Children and Adolescents, 96.4% and 82.4%, respectively. From the result of the multiple regression analysis of SU Tau/Cre and weight we obtained formulas for predicting 24U Tau excretion in Children and Adolescents as follows: Children: 24U Tau = 16.3 (weight) + 314.3 (SU Tau/Cre) -175.2; and Adolescents: 24U Tau = 20.2 (weight) + 644.7 (SU Tau/Cre) - 569.4.

Conclusions

The present study established the regression equation to estimate 24U Tau excretion from SU Tau/Cre and weight. These formulas are expected to contribute to the estimation of fish and SF intake and the follow-up of the change of the dietary behavior by FEP in Children and Adolescents.

Inverse relationship between urinary markers of animal protein intake and blood pressure in Chinese: results from the WHO Cardiovascular Diseases and Alimentary Comparison (CARDIAC) Study

BACKGROUND

This issue of the relationship between animal protein intake and blood pressure (BP) is unsolved. We examined the associations between urinary 3-methylhistidine (3MH) excretion (a biological marker of animal protein intake) and BP in 11 Chinese population samples (Urumqi, Altai, Lhasa, Tulufan, Hetian, Guiyang, Guangzhou, Shanghai, Beijing, Shijiazhuang and Taipei).

METHODS

This was a multi-centre cross-sectional study. In each centre, 100 men and 100 women aged 48-56 years were selected randomly from the general population. 3-methylhistidine in 24-hour (24-h) urine collections was measured by an Amino Acid Analyzer (Hitachi 835, Ibaragi, Japan). The total study sample included 966 men and 1025 women. Subjects who failed to collect complete 24-h urine samples were excluded in data analyses regarding associations between 3MH and BP.

RESULTS

The results showed that: (1) for within-centre analyses of individuals, the 3MH and 3MH to creatinine ratios (3MH:cre) were significantly and negatively associated with BP and hypertension. These associations remained significant after adjustment for age, sex, sodium to potassium ratio, body mass index, calcium and magnesium. The pooled regression coefficients (SE) of systolic blood pressure (SBP) and diastolic blood pressure (DBP) on 3MH were -0.020 (0.01) and -0.018 (0.01), and of SBP and DBP on 3MH:cre were -0.022 (0.01) and -0.016 (0.01), respectively. Subjects with lower 3MH excretion had higher relative risks of hypertension than those who had higher 3MH excretion. (2) In cross-centre analyses, mean SBP and DBP were significantly and negatively associated with the mean 3MH:cre across the 11 population samples (R(2) = 0.56, P < 0.01).

CONCLUSION

The results provide strong evidence that animal protein intake is associated inversely with BP in Chinese populations.

Different associations of blood pressure with 24-hour urinary sodium excretion among pre- and post-menopausal women. WHO Cardiovascular Diseases and Alimentary Comparison (WHO-CARDIAC) Study

OBJECTIVE

Having found no definite relationship between blood pressure (BP) and 24h sodium excretion in women aged 48-56 years (in contrast to the results in men of the same age) in the WHO Cardiovascular Diseases and Alimentary Comparison (WHO-CARDIAC) Study, we analyzed the data to investigate whether the sodium-BP association differed between pre- and post-menopausal women.

DESIGN AND METHODS

The WHO-CARDIAC is a multicenter cross-sectional study, involving, as of July 2000, 60 collaborating centers in 25 countries. In each center, 100 men and 100 women aged 48-56 years were selected randomly from the general population of the area. In this report, 2,212 women in 21 centers located in 17 countries worldwide, who had data on menopausal status, were studied.

RESULTS

After adjustment for age, body mass index (BMI) and 24h urinary potassium excretion, 24h sodium excretion was positively and significantly associated with systolic blood pressure (SBP) [pooled regression coefficient: 0.037 (SE 0.01), P < 0.01] and with diastolic blood pressure (DBP) [0.023 (0.006), P< 0.01] in post-menopausal women. Pooled regression coefficients of sodium-BP association were not significant in pre-menopausal women (P< 0.05). Cross-center correlation analyses of the 21 centers showed that 24h sodium excretion was positively associated with SBP and DBP in both pre- and post-menopausal women, and this positive association between sodium excretion and SBP was significant in post-menopausal women (R2 = 0.23, P = 0.029).

CONCLUSION

Different associations between sodium and BP were observed in women with pre- and post-menopausal status. There may be a tendency for salt sensitivity to increase at the menopause.

Overview: studies on spontaneous hypertension-development from animal models toward man

The development of genetic rat models for research on hypertension, stroke and other cardiovascular diseases (CVD) such as spontaneously hypertensive rats (SHR) and stroke-prone SHR (SHRSP) have contributed not only to the elucidation of the pathogenesis of hypertension-related CVD but also to their prediction and prevention. Since both genetic and environmental factors are involved in the pathogenesis of CVD as extensively studied so far on these models, the detection of the early pathogenic mechanisms related to the genetic factors and the control of environmental factors such as dietary improvement are useful as predictive and preventive measures against CVD. Sympathetic overresponsiveness, early development of cardiovascular hypertrophy, increased salt sensitivity and membrane or transport abnormalities in vascular smooth muscle cells (VSMC) from SHR and SHRSP, possibly related to the pathogenesis of hypertension, are so far regarded as predictors for hypertension partly applicable to human hypertension. Genetic pathogenic mechanisms of stroke in SHRSP which have been proven to be greatly influenced also by dietary factors are hypertension-induced VSMC degeneration and necrosis of intracerebral arteries due to local nutritional disturbance. One of predictors of stroke related to the pathogenic mechanisms is reduction of regional cerebral blood flow. On the other hand, the control of environmental factors, especially nutrition and diets such as intakes of animal and vegetable proteins, some amino acids and fatty acids, potassium, calcium, magnesium, dietary fibers, etc., have been experimentally demonstrated to be effective for the prevention of CVD in these genetic models, and the applicability of these experimental findings to the CVD prevention in man is now supported from our world-wide epidemiological studies (WHO CARDIAC Study).

Experimental intervention of hypertension and cardiovascular diseases

Experimental prevention of hypertension and related cardiovascular diseases has been studied in rat models for hypertension and stroke and not only salt reduction but also increased intakes of potassium, calcium, magnesium, protein, some amino acids and fatty acids and dietary fibers have been proven to be effective and indicated the importance of nonpharmacological dietary prevention of cardiovascular diseases. These experimental findings contribute to dietary risk factor analyses and the prevention of hypertension and its complications in man, as demonstrated by a cross-sectional epidemiological study on cardiovascular diseases and alimentary comparison (WHO-CARDIAC Study).

Preliminary report of cardiac study: cross-sectional multicenter study on dietary factors of cardiovascular diseases. CARDIAC Study Group

The International cooperative 'Cardiovascular Diseases and Alimentary Comparison Study' (CARDIAC Study) was designed to study the relationship of dietary factors to blood pressure (BP) and other major cardiovascular diseases (CVD) in widely different populations of both industrialized and developing countries. The primary aim of the research was to test specific hypotheses linking the intake of certain dietary constituents, e.g., sodium (Na), potassium (K), calcium (Ca) and protein, to BP ('Core' Study); in some centers the relationship between dietary factors and mortality from CVD was also examined ('Complete' Study). The final aim of this multicenter research was to contribute to the scientific information base required to guide the formulation of dietary goals for the primary prevention of major CVD. Forty centers in 20 countries are now participating in the CARDIAC Study. From each population 100 males and 100 females aged 50-54 years were selected randomly for BP measurement by an automated system, 24-hour urine collection by aliquot cups, blood sampling etc. according to CARDIAC protocol; and all samples were analyzed by the WHO Collaborating Center (Izumo) by standardized methods. Although studies are now in progress, surveys in China, Tanzania, USSR and Japan suggest the importance of Na and protein intakes, and all data so far obtained of systolic and diastolic BP, urinary Na and K excretions, serum cholesterol levels, etc. show wide distribution in different populations, so that dietary factors of CVD will be analyzed in more detail when the analyses of total samples are completed.

A simplified system for collecting 24-hour urine samples

A system is described for collecting small aliquots of each voiding. A pool of these samples is returned to the laboratory for calculation of the 24-hr urine volume and for chemical analysis. The components of the system are reusable so that the cost per collection is likely to be less than that of cumbersome large bottles.

Monovalent and divalent cations in hypertension

The relationship of four cations (sodium, potassium, calcium, magnesium) to hypertension is reviewed. It seems reasonable to advise some reduction in sodium intake, and an initial goal of a mean intake of 120 mmole per day for men and 90-100 mmole per day for women is suggested. Some increase in potassium intake may well be justifiable but is better achieved through potassium-containing foods than by any artificial supplements. The data for calcium and magnesium are not sufficiently strong to warrant any recommendation for a change in intake at present.