[Development and evaluation of ExSel Test to screen for excess salt intake in hypertensive subjects]

OBJECTIVE

Development of a test to screen excess salt intake (ESI) in hypertensive patients.

METHODS

Hypertensive subjects living in Paris area have been included. A 24-hour urinary sodium collection has been performed the day before the visit for a day hospital. A food diary was completed on the day of the urine collection and validated after an interview with a dietetician. An ESI was defined by a urinary sodium ≥ 200mmol/d. Clinical or food characteristics associated to an ESI were retained for the ExSel Test variables. A ROC curve was performed to determine the optimal score for the ExSel Test in detection of ESI in hypertensive patients.

RESULTS

One hundred and forty-eight hypertensive patients have been included living in the Île-de-France area. ESI was observed in 19% with a higher frequency in men. Seven major determinants of ESI have been identified and are the questions that constitute the ExSel Test. A positive response assigns points: man (1); BMI > 30 (2); bread 4 or 5 pieces per day (1) or more than 6 pieces; cheese at least 1 time per day (2); charcuterie at least 2 times per week (2); use of processed broth or pilaf (1); food rich in hidden salt (pizza, cheeseburger, quiche, shrimp, potato chips, smoked fish, olive) at least 2 times per week (1). The ROC curve analysis shows that a score of 5 or more has the best Youden index with a sensitivity of 0.63, specificity of 0.95, PPV of 0.75, NPV of 0.92.

CONCLUSIONS

In hypertensive subjects, an excessive salt intake can be detected by the realization of the ExSel Test based only on a simple food-questionnaire and some clinical parameters. For a clinical use of the ExSel Test, an electronic version is available on http://www.comitehta.org.

Measuring population sodium intake: a review of methods

Reduction of population sodium intake has been identified as a key initiative for reduction of Non-Communicable Disease. Monitoring of population sodium intake must accompany public health initiatives aimed at sodium reduction. A number of different methods for estimating dietary sodium intake are currently in use. Dietary assessment is time consuming and often under-estimates intake due to under-reporting and difficulties quantifying sodium concentration in recipes, and discretionary salt. Twenty-four hour urinary collection (widely considered to be the most accurate method) is also burdensome and is limited by under-collection and lack of suitable methodology to accurately identify incomplete samples. Spot urine sampling has recently been identified as a convenient and affordable alternative, but remains highly controversial as a means of monitoring population intake. Studies suggest that while spot urinary sodium is a poor predictor of 24-h excretion in individuals, it may provide population estimates adequate for monitoring. Further research is needed into the accuracy and suitability of spot urine collection in different populations as a means of monitoring sodium intake.

Estimation of daily salt intake through a 24-hour urine collection in Pohang, Korea

There is an established relationship between a high salt diet and public health problems, especially hypertension and cardiovascular disease. We estimated daily salt intake in a group of adults and assessed its association with related variables in Pohang, Korea. We conducted a cross-sectional survey in 2013 with 242 adults. Urine was collected for 24 hr to estimate daily salt intake, and questionnaires about salt preference were administered. The mean daily salt intake was 9.9±4.6 g. There was no difference in salt intake between high systolic blood pressure (SBP) participants and normal SBP participants (10.5±4.7 g/d vs. 9.6±4.3 g/d, P=0.339), but high diastolic blood pressure (DBP) participants reported more salt intake than normal DBP participants (10.4±4.9 g/d vs. 9.7±4.1 g/d, P=0.049). Salt intake and body mass index demonstrated a positive correlation (P=0.001). A preference for Korean soup or stew was associated with high salt intake (P=0.038). Dietary salt intake in Korean adults is still higher than the recommendation from the World Health Organization. More efforts should be made to reduce the salt consumption of Korean adults.

Not salt taste perception but self-reported salt eating habit predicts actual salt intake

Excessive dietary salt intake is related to cardiovascular morbidity and mortality. Although dietary salt restriction is essential, it is difficult to achieve because of salt palatability. However, the association between salt perception or salt eating habit and actual salt intake remains uncertain. In this study, we recruited 74 healthy young individuals. We investigated their salt-eating habits by questionnaire and salt taste threshold through a rating scale that used serial dilution of a sodium chloride solution. Predicted 24-hr urinary salt excretions using Kawasaki's and Tanaka's equations estimated dietary salt intake. Participants' mean age was 35 yr, and 59.5% were male. Salt sense threshold did not show any relationship with actual salt intake and a salt-eating habit. However, those eating "salty" foods showed higher blood pressure (P for trend=0.048) and higher body mass index (BMI; P for trend=0.043). Moreover, a salty eating habit was a significant predictor for actual salt intake (regression coefficient [β] for Kawasaki's equation 1.35, 95% confidence interval [CI] 10-2.69, P=0.048; β for Tanaka's equation 0.66, 95% CI 0.01-1.31, P=0.047). In conclusion, a self-reported salt-eating habit, not salt taste threshold predicts actual salt intake.

Monitoring salt and iodine intakes in Dutch adults between 2006 and 2010 using 24 h urinary sodium and iodine excretions

OBJECTIVE

To monitor the effectiveness of salt-reduction initiatives in processed foods and changes in Dutch iodine policy on Na and iodine intakes in Dutch adults between 2006 and 2010.

DESIGN

Two cross-sectional studies among adults, conducted in 2006 and 2010, using identical protocols. Participants collected single 24 h urine samples and completed two short questionnaires on food consumption and urine collection procedures. Daily intakes of salt, iodine, K and Na:K were estimated, based on the analysis of Na, K and iodine excreted in urine.

SETTING

Doetinchem, the Netherlands.

SUBJECTS

Men and women aged 19 to 70 years were recruited through random sampling of the Doetinchem population and among participants of the Doetinchem Cohort Study (2006: n 317, mean age 48·9 years, 43 % men; 2010: n 342, mean age 46·2 years, 45 % men).

RESULTS

While median iodine intake was lower in 2010 (179 μg/d) compared with 2006 (257 μg/d; P < 0·0001), no difference in median salt intake was observed (8·7 g/d in 2006 v. 8·5 g/d in 2010, P = 0·70). In 2006, median K intake was 2·6 g/d v. 2·8 g/d in 2010 (P < 0·01). In this 4-year period, median Na:K improved from 2·4 in 2006 to 2·2 in 2010 (P < 0·001).

CONCLUSIONS

Despite initiatives to lower salt in processed foods, dietary salt intake in this population remains well above the recommended intake of 6 g/d. Iodine intake is still adequate, although a decline was observed between 2006 and 2010. This reduction is probably due to changes in iodine policy.

How much salt do adults consume in climate vulnerable coastal Bangladesh?

BACKGROUND

Evidence from numerous studies suggests that salt intake is an important determinant of elevated blood pressure. Robust data about salt consumption among adults in Bangladesh is sparse. However, much evidence suggests saline intrusion due to sea level rise as a result of climate change exposes more than 20 million people to adverse effects of salinity through the food and water supply. The objective of our study was to assess salt consumption among adults in a coastal region of Bangladesh.

METHODS

Our study was cross sectional and conducted during October-November 2011. A single 24 hour urine was collected from 400 randomly selected individuals over 18 years of age from Chakaria, a rural, coastal area in Southeastern Bangladesh. Logistic regression was conducted to identify the determinants of high salt consumption.

RESULTS

The mean urinary sodium excretion was 115 mmol/d (6.8 g salt). Based on logistic regression using two different cutoff points (IOM and WHO), housewives and those living in the coastal area had a significantly higher probability of high salt intake compared with people who were engaged in labour-intensive occupations and who lived in hilly areas.

CONCLUSION

It is important to create awareness about the implication of excessive salt intake on health and to develop strategies for reducing salt intake that can be implemented at the community-level. A sustainable policy for salt reduction in the Bangladeshi diet should be formulated with special emphasis on coastal areas.

Salt intake assessed by 24 h urinary sodium excretion in a random and opportunistic sample in Australia

OBJECTIVE

The gold standard method for measuring population sodium intake is based on a 24 h urine collection carried out in a random population sample. However, because participant burden is high, response rates are typically low with less than one in four agreeing to provide specimens. At this low level of response it is possible that simply asking for volunteers would produce the same results.

SETTING

Lithgow, New South Wales, Australia.

PARTICIPANTS

We randomly selected 2152 adults and obtained usable 24 h urine samples from 306 (response rate 16%). Specimens were also collected from a further 113 volunteers. Estimated salt consumption and the costs for each strategy were compared.

RESULTS

The characteristics of the 'random' and 'volunteer' samples were moderately different in mean age 58 (SD 14.6 vs 49(17.7) years, respectively; p<0.001) as well as self-reported alcohol use, tobacco use, history of hypertension and prescription drug use (all p<0.04). Overall crude mean 24 h urinary salt excretion was 8.9(3.6) g/day in the random sample vs 8.5(3.3) g/day for the volunteers (p=0.42). Corresponding age-adjusted and sex-adjusted estimates were 9.2(3.3) and 8.8(3.4) g/day (p=0.29). Estimates for men 10.3(3.8) vs 9.6(3.3) g/day; (p=0.26) and women 7.6(3) vs 7.9(3.2) g/day; (p=0.43) were also similar for the two samples, as was salt excretion across age groups (p=0.72). The cost of obtaining each 24 h urine sample was two times greater for the random compared to volunteer samples ($A62 vs $A31).

CONCLUSIONS

The estimated salt consumption derived from the two samples was comparable and was not substantively different to estimates obtained from other surveys. In countries where salt is pervasive and cannot easily be avoided, estimates of consumption obtained from volunteer samples may be valid and less costly.

[Complex strategies for management of child health in districts of endemic iodine deficiency in the Saratov region]

In the article there is presented an analysis of clusters of the formation of iodine deficiency in schoolchildren of the Saratov region. There is given a hygienic assessment of iodine content in food raw materials and food, grown and produced in the territory of the region. For various groups of food the low content of trace element iodine was shown to be typical. The analysis of the quality and diversity of iodized salt sold in the trading network of the region has been performed. The formation of the mass iodine deficiency states in the Saratov region was shown to bear a longtime character According to the results of urine screening studies of examined children of organized groups an average level of iodine deficiency has been revealed.

[Influence factors of salt-sensitive hypertension and responses of blood pressure and urinary sodium and potassium excretion to acute oral saline loading among essential hypertensive patients]

OBJECTIVE

To explore the influence factors of salt-sensitive hypertension and to observe changes of blood pressures and urinary sodium and potassium excretion in response to acute oral saline loading among essential hypertensive patients in China.

METHODS

Essential hypertensive patients from Beijing Jinzhan second community were included in this study. Salt-sensitivity was determined via the improved Sullivan's acute oral saline loading and furosemide volume-depletion tests. Binary logistic regression analysis was applied to explore influence factors of salt-sensitive hypertension. Acute oral saline loading induced changes on blood pressures and urinary sodium and potassium excretion were observed.

RESULTS

Sixty-three salt-sensitive hypertensive patients were classified out of a total of 342(18.4%) essential hypertensive patients. Salt-sensitive patients were elder than the non-salt-sensitive patients (P < 0.05) . Binary logistic regression analysis showed that age (OR = 1.744, 95%CI:0.922-3.300, P > 0.05) , gender (OR = 0.728, 95%CI:0.374-1.415, P > 0.05) , total cholesterol level (OR = 1.168, 95%CI:0.882-1.547, P > 0.05) and 24-hour urinary sodium (OR = 0.998, 95%CI:0.995-1.002, P > 0.05) were not influencing factors of salt-sensitivity among essential hypertensive patients. Bivariate general linear models for repeated measures showed that there were significant statistical differences on blood pressures and urinary electrolytes concentrations between the beginning of trials, 2 hours after acute saline loading and 2 hours after furosemide volume-depletion(all P < 0.01). There was a greater blood pressures change in salt-sensitive patients than in non-salt-sensitive patients(all P < 0.01) while urinary electrolytes concentrations change was similar between two groups(all P > 0.05).

CONCLUSIONS

Age, gender, total cholesterol level and 24-hour urinary sodium are not influencing factors of salt-sensitivity among essential hypertensive patients in this study. Impaired pressure natriuresis during acute oral saline loading and furosemide volume-depletion tests is presented in salt-sensitive essential hypertensive patients.

Iodine contributes to thyroid autoimmunity in humans by unmasking a cryptic epitope on thyroglobulin

CONTEXT

The mechanisms linking thyroid autoimmunity and iodine use in humans are unknown.

OBJECTIVE

Our aim was to correlate iodine intake, thyroid autoimmunity, and recognition of thyroglobulin (Tg) epitopes after implementation of iodine prophylaxis.

SETTING

The general community living in an Italian village was evaluated.

MAIN OUTCOME MEASURES

Thyroglobulin autoantibodies (TgAb), thyroperoxidase autoantibodies (TPOAb), and urinary iodine excretion were assessed in 906 iodized salt users (IS-users) and 389 nonusers (IS-nonusers). Ultrasound (US) was performed to identify thyroid hypoechogenicity, suggestive of Hashimoto thyroiditis (HT). TgAb epitope pattern in 16 IS-users and 17 IS-nonusers was evaluated by an inhibition binding assay to Tg, using human monoclonal TgAb-Fab directed to A, B, C, and D epitopes on Tg.

RESULTS

Median urinary iodine excretion was slightly higher in IS-users than in IS-nonusers (112.0 μg/L vs 86.5 μg/L; P < .01). TgAb, and not TPOAb, was more frequent in IS-users (18.9% vs 13.6%, P = .02). HT-US was found in 87 subjects, among whom both positive TgAb (58.4% vs 31.8%, P = .03) and TPOAb (61.5% vs 45.4%. P = .04) were more frequent in IS-users. In this group significantly higher serum levels of TgAb (median 108 U/mL vs 30 U/mL; P = .02), but not of TPOAb, were present. Iodized salt use had no effect on the 1208 non HT-US subjects. TgAb directed to the epitope B of Tg were more frequent in IS-users than in IS-nonusers (27.5% vs 3.0%, P = .047).

CONCLUSIONS

Iodine-induced thyroid autoimmunity is related to TgAb and the unmasking of a cryptic epitope on Tg contributes to this relationship in humans.

Effect of longer term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomised trials

OBJECTIVE

To determine the effects of longer term modest salt reduction on blood pressure, hormones, and lipids.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Medline, Embase, Cochrane Hypertension Group Specialised Register, Cochrane Central Register of Controlled Trials, and reference list of relevant articles.

INCLUSION CRITERIA

Randomised trials with a modest reduction in salt intake and duration of at least four weeks.

DATA EXTRACTION AND ANALYSIS

Data were extracted independently by two reviewers. Random effects meta-analyses, subgroup analyses, and meta-regression were performed.

RESULTS

Thirty four trials (3230 participants) were included. Meta-analysis showed that the mean change in urinary sodium (reduced salt v usual salt) was -75 mmol/24 h (equivalent to a reduction of 4.4 g/day salt), and with this reduction in salt intake, the mean change in blood pressure was -4.18 mm Hg (95% confidence interval -5.18 to -3.18, I(2)=75%) for systolic blood pressure and -2.06 mm Hg (-2.67 to -1.45, I(2)=68%) for diastolic blood pressure. Meta-regression showed that age, ethnic group, blood pressure status (hypertensive or normotensive), and the change in 24 hour urinary sodium were all significantly associated with the fall in systolic blood pressure, explaining 68% of the variance between studies. A 100 mmol reduction in 24 hour urinary sodium (6 g/day salt) was associated with a fall in systolic blood pressure of 5.8 mm Hg (2.5 to 9.2, P=0.001) after adjustment for age, ethnic group, and blood pressure status. For diastolic blood pressure, age, ethnic group, blood pressure status, and the change in 24 hour urinary sodium explained 41% of the variance between studies. Meta-analysis by subgroup showed that in people with hypertension the mean effect was -5.39 mm Hg (-6.62 to -4.15, I(2)=61%) for systolic blood pressure and -2.82 mm Hg (-3.54 to -2.11, I(2)=52%) for diastolic blood pressure. In normotensive people, the figures were -2.42 mm Hg (-3.56 to -1.29, I(2)=66%) and -1.00 mm Hg (-1.85 to -0.15, I(2)=66%), respectively. Further subgroup analysis showed that the decrease in systolic blood pressure was significant in both white and black people and in men and women. Meta-analysis of data on hormones and lipids showed that the mean change was 0.26 ng/mL/h (0.17 to 0.36, I(2)=70%) for plasma renin activity, 73.20 pmol/L (44.92 to 101.48, I(2)=62%) for aldosterone, 187 pmol/L (39 to 336, I(2)=5%) for noradrenaline (norepinephrine), 37 pmol/L (-1 to 74, I(2)=12%) for adrenaline (epinephrine), 0.05 mmol/L (-0.02 to 0.11, I(2)=0%) for total cholesterol, 0.05 mmol/L (-0.01 to 0.12, I(2)=0%) for low density lipoprotein cholesterol, -0.02 mmol/L (-0.06 to 0.01, I(2)=16%) for high density lipoprotein cholesterol, and 0.04 mmol/L (-0.02 to 0.09, I(2)=0%) for triglycerides.

CONCLUSIONS

A modest reduction in salt intake for four or more weeks causes significant and, from a population viewpoint, important falls in blood pressure in both hypertensive and normotensive individuals, irrespective of sex and ethnic group. Salt reduction is associated with a small physiological increase in plasma renin activity, aldosterone, and noradrenaline and no significant change in lipid concentrations. These results support a reduction in population salt intake, which will lower population blood pressure and thereby reduce cardiovascular disease. The observed significant association between the reduction in 24 hour urinary sodium and the fall in systolic blood pressure, indicates that larger reductions in salt intake will lead to larger falls in systolic blood pressure. The current recommendations to reduce salt intake from 9-12 to 5-6 g/day will have a major effect on blood pressure, but a further reduction to 3 g/day will have a greater effect and should become the long term target for population salt intake.

The relationship between cognitive function, depressive behaviour and sleep quality with 24-h urinary sodium excretion in patients with essential hypertension

BACKGROUND

Various studies have shown that sodium intake is related to increased blood pressure. However, the relationship between sodium intake and cognitive function and depression has not previously been studied.

AIM

The objective of this study was to investigate the relationship between 24-h sodium excretion with cognitive function, depression and sleep quality in patients newly diagnosed with essential hypertension.

METHODS

All patients underwent history taking, physical examination, blood pressure measurement, 12-lead ECG evaluation, routine urine analysis, biochemical analysis and 24-h urine collection to measure urinary sodium and protein excretion and creatinine clearance, evaluation of cognitive function, depressive behaviour and sleep quality.

RESULTS

In total, 119 patients newly diagnosed with essential hypertension (50 men and 69 women aged 54.2 ± 16.1 years) were enrolled. The 24-h urinary sodium excretion of the patients was 204.0 ± 240.4 mEq/day. The Standardized Mini Mental State Examination (SMMSE), Pittsburgh Sleep Quality Index and Beck Depression Inventory scores of the patients were 26.0 ± 2.7, 5.6 ± 3.1 and 21.6 ± 13.5, respectively. Spearman correlation analysis revealed that 24-h urinary sodium excretion was correlated with age (rho -0.258, p = 0.005), systolic blood pressure (rho 0.219, p = 0.017), diastolic blood pressure (rho 0.195, p = 0.034), creatinine clearance (rho 0.414, p < 0.0001) and SMMSE score (rho -0.257, p = 0.005). Stepwise linear regression of independent factors revealed that gender (p < 0.0001), creatinine clearance (p < 0.0001), systolic blood pressure (p = 0.031) and SMMSE score (p < 0.0001) were independently related to logarithmically converted 24-h sodium excretion.

CONCLUSION

The current study demonstrated that better cognitive function, but not depressive behaviour and sleep disturbance, is related to decreased sodium intake as evaluated by 24-h urinary sodium excretion. Studies are needed to highlight the mechanisms regarding the relationship between cognitive function and sodium intake.

Iodized salt supplementation and its effects on thyroid status amongst Orang Asli in Hulu Selangor, Malaysia

BACKGROUND

This research was performed to determine the prevalence of iodine deficiency disorder (IDD) and the effects of iodized salt supplementation on thyroid status amongst Orang Asli in Hulu Selangor, Malaysia.

METHODS

Study respondents were from three target groups, i.e. pre-school children (PSC), primary school-going children (SGC) and adult women. Each household was supplied with iodized salt fortified with iodate fortificant for a period of 12 months and the iodine levels in the salt ranged from 20 to 30 μg/L. Samples collected before and after 6 and 12 months of introduction to iodized salt were urine from all groups, as well as serum samples from adult women.

RESULTS

A total of 200 respondents were recruited; 58 (29.0%) PSC, 65 (32.5%) SGC and 77 (38.5%) adult women. The median urine-iodine concentration (mUIC) in all groups were of moderately low before the iodized salt intervention, but increased significantly in all study groups after 6 and 12 months of intervention. However, at the end of the study, there was an increase in severe iodine deficiency (mUIC <20 μg/L) from 7.5% to 12% and about 9% of PSC and SGC respondents had mUIC level of more than 300 μg/L while the adult women showed a significant increase in free triiodothyronine (fT3) levels.

CONCLUSION

The study demonstrated that iodized salt supplementation was able to show an improvement in iodine level amongst Orang Asli. However, an increase in severe iodine deficiency and iodine excess indicated that the iodized salt programme needs to be carefully monitored.

[Analysis of urine iodine level and its influencing factors in Zhejiang from 2009 to 2011]

OBJECTIVE

To evaluate the iodine nutrition level of population in Zhejiang province and to analyze the relevant influencing factors from 2009 to 2011.

METHODS

From October 2009 to October 2011, a total of 19 517 subjects were recruited in this cross sectional survey, by multistage stratified cluster random sampling method. The subjects were all living over three years in Zhejiang province. The basic information and life styles were interviewed by questionnaires; and the samples of drinking water, edible salt and urines were separately collected from the subjects to test the content of iodine. In total, 16 228 subjects answered the questionnaire, and 265 samples of drinking water, 7811 samples of edible salt and 19 517 samples of urine were collected. Then, we analyzed the distribution of iodine in water, edible salt and urine samples, as well as the relevance.

RESULTS

The median (25% - 75% percentile) of water iodine was 2.42 (1.17 - 6.28) µg/L in drinking water among Zhejiang residents; while separately 2.79 (1.60 - 6.87) µg/L in city and 2.04 (1.03 - 5.29) µg/L in country side (Z = 2.07, P < 0.05). The figures turned out to be 2.17 (1.22 - 5.73) µg/L, 2.77 (1.88 - 6.87) µg/L, and 1.40 (0.77 - 5.65) µg/L, respectively, in coastal areas, coastal periphery areas and inland areas (χ(2) = 11.16, P < 0.05). The median (25% - 75% percentile) of salt iodine was 28.80 (22.93 - 32.40) mg/kg; while separately 29.00 (24.50 - 32.60) mg/kg and 28.50 (13.90 - 32.29) mg/kg in city and country side (Z = 6.32, P < 0.05). The figures turned out to be 25.19 (0.00 - 30.20) mg/kg, 29.00 (26.60 - 31.70) mg/kg and 32.40 (28.94 - 36.30) mg/kg, respectively, in coastal areas, coastal periphery areas and inland areas (χ(2) = 1581.62, P < 0.05). The coverage rate of iodized salt was 79.54% (6213/7811) in all province. The urinary iodine median was 160.74(97.20 - 247.00) µg/L, while the urinary iodine median in pregnant women was 137.99 (82.40 - 215.30) µg/L, lower than the recommended optimal levels, which was 150 - 249 µg/L. The figures turned out to be 153.45(92.00 - 237.50) µg/L in city and 168.00 (102.18 - 257.00) µg/L in country side (Z = -9.25, P < 0.05); while in coastal, coastal periphery place and inland areas, the median were separately 156.00 (94.29 - 242.80) µg/L, 150.14 (94.70 - 227.00) µg/L and 187.70 (109.00 - 276.80) µg/L (χ(2) = 194.12, P < 0.05). The analysis of relevance between urine iodine, water iodine and iodized salt showed that the urine iodine would increase as long as the iodized salt increased; and the difference had statistical significance (χ(2) = 440.88, P < 0.01). And there were no relevance between urine iodine level and the water iodine level (χ(2)cmh = 0.57, P = 0.45). The analysis of the influencing factors showed that education background (χ(2) = 14.17, P < 0.05), different styles of career (χ(2) = 16.15, P < 0.01) and diet habits (χ(2) = 108.63, P < 0.01) could influence the level of urine iodine.

CONCLUSION

Iodine was deficient in Zhejiang province. The nutrition level of iodine was fine in Zhejiang in 2009, however, the coverage rate of iodine was commonly low in coastal areas, especially the pregnant women suffered from iodine deficiency. In our study, the factors influencing the urine iodine level included iodized salt, age, education background and diet habits.

National approaches to monitoring population salt intake: a trade-off between accuracy and practicality?

Aims

There is strong evidence that diets high in salt are bad for health and that salt reduction strategies are cost effective. However, whilst it is clear that most people are eating too much salt, obtaining an accurate assessment of population salt intake is not straightforward, particularly in resource poor settings. The objective of this study is to identify what approaches governments are taking to monitoring salt intake, with the ultimate goal of identifying what actions are needed to address challenges to monitoring salt intake, especially in low and middle-income countries.

Methods and Results

A written survey was issued to governments to establish the details of their monitoring methods. Of the 30 countries that reported conducting formal government salt monitoring activities, 73% were high income countries. Less than half of the 30 countries, used the most accurate assessment of salt through 24 hour urine, and only two of these were developing countries. The remainder mainly relied on estimates through dietary surveys.

Conclusions

The study identified a strong need to establish more practical ways of assessing salt intake as well as technical support and advice to ensure that low and middle income countries can implement salt monitoring activities effectively.

Japanese traditional miso soup attenuates salt-induced hypertension and its organ damage in Dahl salt-sensitive rats

OBJECTIVE

We investigated the effects of long-term miso soup drinking on salt-induced hypertension in Dahl salt-sensitive (Dahl S) rats.

METHODS

Dahl S rats were divided into four groups that consumed 1) water, 2) a 0.9% NaCl solution, 3) a 1.3% sodium NaCl solution, or 4) miso soup containing 1.3% NaCl. They were followed for 8 wk. Systolic blood pressure and hypertensive organ damage were determined.

RESULTS

Systolic blood pressure increased in an age- and dose-dependent manner in Dahl S rats drinking salt solutions. The systolic blood pressure increase was significantly less in the Dahl S rats that drank miso soup, although the ultimate cumulative salt loading was greater than that in the Dahl S rats given the 1.3% NaCl solution. This blood pressure decrease was associated with a morphologic attenuation of glomerular sclerosis in the kidney and collagen infiltration in the heart. Urinary protein excretions were less in the miso group than in the rats given the 1.3% NaCl solution. The fractional excretion of sodium was increased and that of potassium was decreased in Dahl S rats given the 1.3% NaCl solution, and these effects were reversed in rats given miso soup toward the values of the control.

CONCLUSION

We found that long-term miso soup drinking attenuates the blood pressure increase in salt-induced hypertension with organ damage. This may be caused by a possible retardation of sodium absorption in the gastrointestinal tract or by the direct effects of nutrients in the miso soup from soybeans. The decrease was associated with decreases in cardiovascular and renal damage.

Patterns of sodium and potassium excretion and blood pressure in the African Diaspora

Habitual levels of dietary sodium and potassium are correlated with age-related increases in blood pressure (BP) and likely have a role in this phenomenon. Although extensive published evidence exists from randomized trials, relatively few large-scale community surveys with multiple 24-h urine collections have been reported. We obtained three 24-h samples from 2704 individuals from Nigeria, Jamaica and the United States to evaluate patterns of intake and within-person relationships with BP. The average (±s.d.) age and weight of the participants across all the three sites were 39.9±8.6 years and 76.1±21.2 kg, respectively, and 55% of the total participants were females. Sodium excretion increased across the East-West gradient (for example, 123.9±54.6, 134.1±48.8, 176.6±71.0 (±s.d.) mmol, Nigeria, Jamaica and US, respectively), whereas potassium was essentially unchanged (for example, 46.3±22.9, 40.7±16.1, 44.7±16.4 (±s.d.) mmol, respectively). In multivariate analyses both sodium (positively) and potassium (negatively) were strongly correlated with BP (P<0.001); quantitatively the association was stronger, and more consistent in each site individually, for potassium. The within-population day-to-day variation was also greater for sodium than for potassium. Among each population group, a significant correlation was observed between sodium and urine volume, supporting the prior finding of sodium as a determinant of fluid intake in free-living individuals. These data confirm the consistency with the possible role of dietary electrolytes as hypertension risk factors, reinforcing the relevance of potassium in these populations.

Does iodine gas released from seaweed contribute to dietary iodine intake?

Thyroid hormone levels sufficient for brain development and normal metabolism require a minimal supply of iodine, mainly dietary. Living near the sea may confer advantages for iodine intake. Iodine (I(2)) gas released from seaweeds may, through respiration, supply a significant fraction of daily iodine requirements. Gaseous iodine released over seaweed beds was measured by a new gas chromatography-mass spectrometry (GC-MS)-based method and iodine intake assessed by measuring urinary iodine (UI) excretion. Urine samples were obtained from female schoolchildren living in coastal seaweed rich and low seaweed abundance and inland areas of Ireland. Median I(2) ranged 154-905 pg/L (daytime downwind), with higher values (~1,287 pg/L) on still nights, 1,145-3,132 pg/L (over seaweed). A rough estimate of daily gaseous iodine intake in coastal areas, based upon an arbitrary respiration of 10,000L, ranged from 1 to 20 μg/day. Despite this relatively low potential I(2) intake, UI in populations living near a seaweed hotspot were much higher than in lower abundance seaweed coastal or inland areas (158, 71 and 58 μg/L, respectively). Higher values >150 μg/L were observed in 45.6% of (seaweed rich), 3.6% (lower seaweed), 2.3% (inland)) supporting the hypothesis that iodine intake in coastal regions may be dependent on seaweed abundance rather than proximity to the sea. The findings do not exclude the possibility of a significant role for iodine inhalation in influencing iodine status. Despite lacking iodized salt, coastal communities in seaweed-rich areas can maintain an adequate iodine supply. This observation brings new meaning to the expression "Sea air is good for you!"

Patterns of iodine intake and urinary iodine concentrations during pregnancy and blood thyroid-stimulating hormone concentrations in the newborn progeny

BACKGROUND

Appropriate maternal intake of iodine during pregnancy is essential for maternal thyroxine production and thyroid status of the fetus. It should be possible to enhance iodine intake during pregnancy by using iodine fortified salt or taking iodine supplements. In the present report we determined the status of iodine nutrition in pregnant women who were stratified on the basis of their history of taking or not taking iodized salt or iodine supplements. The study was performed in Toledo (Spain), a region in which prior studies have noted borderline iodine sufficiency. Iodine nutrition was assessed by measuring urinary iodine concentration (UIC) and neonatal thyrotropin (TSH).

METHODS

UIC was measured in 525 pregnant women. They were grouped according to their history of iodine intake. Diet Group 1 patients (n = 69) did not take iodized salt or iodine supplements during pregnancy. Diet Group 2 patients (n = 75) took iodized salt but not iodine supplements during pregnancy. Diet Group 3 patients (n = 381) took iodine supplements during pregnancy. Plasma determinations included TSH, free thyroxine, thyroid peroxidase antibody, and thyroglobulin antibody. UIC was measured in a single urine sample from all the pregnant women. Neonatal TSH was measured in capillary spot blood from all the neonates as part of a screening for congenital metabolic abnormalities.

RESULTS

The median UIC in all subjects was 164 μg/L (interquartile range [IR]: 116-245). The median UICs in Diet Groups 1, 2, and 3 were 134.5 (IR: 90-196), 146 (IR: 103-205), and 183 (IR: 124-261) μg/L, respectively (p = not significant [NS] for Diet Group 1 vs. 2; p < 0.01 for Diet Group 2 vs. 3; all other comparisons NS). The median (IR) TSH of the neonates in all Diet Groups was 1.0 (IR: 0.7-1.6) μU/mL. Only 2 neonates had blood TSH concentrations >5 mU/L. Neonatal blood TSH concentrations were similar in all Diet Groups.

CONCLUSIONS

In a region with a history of borderline iodine deficiency the UICs were below 150 μg/L in a substantial percentage of pregnant women who did not take iodine supplements, regardless of whether or not they took iodized salt. Our results support the use of iodine supplements from the start of the pregnancy, or even before pregnancy in women who live in regions with a history of even small degrees of iodine deficiency. In addition, neonate TSH screening is not the best tool to assess whether the iodine status in populations is ideal.

[Syndrome of hypovolemia in patients with arterial hypertension]

A total of 440 patients with essential arterial hypertension underwent measurement of daily sodium excretion in urine followed by calculation of table salt consumption, 24-hour monitoring of AP and determination of daily AP index. Patients divided into 3 groups of n = 98, 120 and 222 were estimated to daily consume 9, 12 and 16 or more gram of salt respectively. Clinical manifestations of arterial hypertension and AP values progressively increased from group 1 to 3. These changes were paralleled by increased requirement of hypotensive agents, AP variations, and the number of non-dippers and night-pickers. It is concluded that the above features of AH correlate with salt consumption and are related to hypervolemia.

[Field study on the change of urinary iodine levels among family members with iodine content of 5 - 150 microg/L in drinking water before and after non-iodized salt intervention]

OBJECTIVE

To compare the changes of urinary iodine levels among the family members with iodine content of 5 - 150 microg/L in drinking water, before and after non-iodized salt intervention through a field trail study.

METHODS

Family members who routinely drank water with iodine content 5 - 150 microg/L were chosen to substitute non-iodized salt for their current iodized salt for 2 months, and urine samples of the family members were collected for determination of iodine change before and after intervention was carried out.

RESULTS

Median urinary iodine of school children, women with productive age and male adults exceeding 370 microg/L before intervention and the frequency distribution of urinary iodine were all above 70%. Our results revealed that iodine excess exited in three groups of family members. After intervention, all median urinary iodine level seemed to have decreased significantly, and groups with drinking water iodine 5.0 - 99.9 microg/L reduced to adequate or close to adequate while the group that drinking water iodine was 100 - 150 microg/L reached the cut-off point of excessive iodine level (300 microg/L).

CONCLUSION

Results from your study posed the idea that the iodine adequate areas should be defined as the areas with iodine content of 5.0 - 100 microg/L in drinking water, and edible salt not be iodized in these areas. Areas with iodine content of 100 - 150 microg/L in drinking water should be classified as iodine excessive.

[Analysis on the feasibility of reducing the concentration in edible iodine-salt based on the results of iodized salt monitoring program from the year of 2004 to 2006, in China]

OBJECTIVE

To analyze the feasibility of reducing the concentration of iodized salt based on the results of iodized salt monitoring from the year of 2004 to 2006.

METHODS

Special software for iodized salt monitor and SAS 9.0 were used to analyze salt monitoring data and urine iodine data of women at reproductive age in high-risk areas in 2006.

RESULTS

Based on the data from monitoring program, adequate iodized salt coverage increased constantly in China. The quality of iodized salt was stable with less than 2 mg/kg iodine loss at production level but most was at 3 mg/kg iodine loss under estimation during the process of distribution from factory to households. Individual daily intake of iodized salt was higher than the recommendation from WHO but the average level of urinary iodine excretion of women and school children was more than adequate.

CONCLUSION

To decrease the concentration of iodine in edible salt was necessary in China. Our findings provided recommendation on the concentration of iodine in edible salt that should be adjusted from the current concentration of 35 mg/kg to 25-28 mg/kg, and the variation should be controlled from the current range of +/- 15 mg/kg to +/- 10 mg/kg.

Goiter rate, serum thyrotropin, thyroid autoantibodies and urinary iodine concentration in Tehranian adults before and after national salt iodization

Goiter rate, serum TSH, antithyroperoxidase (TPOAb), antithyroglobulin (TgAb) antibodies, and urinary iodine concentration (UIC) were evaluated 10-11 yr prior (1983-1984) and 5-6 yr after (1999-2000) national salt iodization in Iran. Pre- and post-iodization groups consisted of 465 and 1426 adults aged > or =20 yr, respectively, selected by random cluster sampling in Tehran province. Total, grade 1 and grade 2 goiter rates were 65.2, 53.1, and 12.1% in 1983-1984 vs 25.2, 15.5, and 9.7% in 1999-2000 (p<0.0001). Median serum TSH was 1.5 mIU/l in 1983-1984 vs 0.8 mIU/l in 1999-2000 (p<0.0001). Median TSH also decreased in 20-29, 30-39, 40-49, 50-59, and > or =60- yr-adults in 1983-1984 vs 1999-2000 (p<0.0001). In 1983-1984, positive TPOAb and positive TgAb were detected in 3.2 and 4%, respectively, using agglutination test. Corresponding values were 12.5 and 16.8% using immunoenzymometric assay in 1999-2000. Overt and subclinical hypothyroidism was present in 0 and 32.8/1000 in 1983-1984 vs 3.5 and 21.7/1000 in 1999-2000, respectively. Overt and subclinical hyperthyroidism was detected in 4.4 and 4.4/1000 in 1983-1984 vs 0.7 and 5.6/1000 in 1999-2000, respectively. Subclinical hypothyroidism in males was significantly more frequent in 1983-1984 vs 1999-2000 (odds ratio 5.02, 95% confidence interval 1.72-14.68; p=0.004). Salt iodization resulted in adequate UIC, decrease in serum TSH and subclinical hypothyroidism in males, and an increase in thyroid autoantibodies without significant change in thyroid abnormalities. Benefits of iodine supplementation far outweigh its hazards in Tehranian adults.

Salt usage behaviors are related to urinary sodium excretion in normotensive Korean adults

High sodium intake is considered to be the major risk factor for hypertension but studies about sodium intake on prevention and management of hypertension is limited due to the difficulties in assessment of sodium intake. Dietary sodium comes not only from naturally occurring sodium in foods but also from the added sodium during processing, cooking and at the table. Present study was conducted to identify salt usage behavior questions related to urinary sodium excretion among normotensive adult Koreans. The test version of the salt usage questionnaire included six items of salt usage behaviors and nine items of high salt containing foods. A survey was conducted in 189 adults over 18 years of age in three age groups in both genders. Each participant answered the questionnaire and collected one 24-hour urine and urine samples were analyzed for sodium contents. Correlation analyses between scores of the questions and sodium excretion in 24-hour urine were performed to identify question items related to sodium excretion. Among fifteen questions, scores of three questions on salt usage behaviors were significantly correlated to urinary sodium excretion (r=0.17~0.19; p <0.05) and the sum of scores of the three questions showed higher correlation coefficients. (r=0.26, p <0.001) The salt usage behavior questions developed in this study would be useful in predicting sodium intake and in studying the relationship between sodium intake and health among Korean adults.

Effectiveness of a spot urine method in evaluating daily salt intake in hypertensive patients taking oral antihypertensive drugs

Kawasaki et al. developed a spot urine method (SUM) for evaluating daily salt intake using one pre-breakfast sample obtained after initial voiding upon arising. Their subjects were healthy persons who were not taking any regular medications. To determine whether SUM can be successfully used for patients taking antihypertensive drugs, we estimated daily salt intake in 73 hypertensive patients by SUM and by a food consumption method (FCM) when they were at home, and also by SUM in the hospital with a defined intake of 7 g of sodium chloride (NaCl). Forty-one patients took oral antihypertensive medications once daily, while 32 patients took none. Mean daily salt intakes by SUM during admission were 7-8 g of NaCl in both groups (95% confidence intervals: 5.0-10.6 g in the medication group; 5.2-11.1 g in the no-medication group), which corresponded well to the diet. In contrast, ambulatory daily salt intake by SUM varied widely (95% confidence intervals: 5.5-20.7 g in the medication group; 7.6-22.8 g in the no-medication group). However, the daily salt intakes determined by SUM and FCM correlated significantly with each other in the medication group (r=0.69, p<0.01) and the no-medication group (r=0.66, p<0.01). SUM is therefore a reliable method for evaluating daily salt intake in patients taking antihypertensive medication as well as unmedicated patients.

Collecting duct-specific knockout of the endothelin B receptor causes hypertension and sodium retention

Collecting duct (CD)-derived endothelin-1 (ET-1) inhibits renal Na reabsorption and its deficiency increases blood pressure (BP). The role of CD endothelin B (ETB) receptors in mediating these effects is unknown. CD-specific knockout of the ETB receptor was achieved using an aquaporin-2 promoter-Cre recombinase transgene and the loxP-flanked ETB receptor gene (CD ETB KO). Systolic BP in mice with CD-specific knockout of the ETB receptor, ETA receptor (CD ETA KO) and ET-1 (CD ET-1 KO), and their respective controls were compared during normal- and high-salt diet. On a normal-sodium diet, CD ETB KO mice had elevated BP, which increased further during high salt feeding. However, the degree of hypertension in CD ETB KO mice and the further increase in BP during salt feeding were lower than that of CD ET-1 KO mice, whereas CD ETA KO mice were normotensive. CD ETB KO mice had impaired sodium excretion following acute sodium loading. Aldosterone and plasma renin activity were decreased in CD ETB KO mice on normal- and high-sodium diets, while plasma and urinary ET-1 levels did not differ from controls. In conclusion, the CD ETB receptor partially mediates the antihypertensive and natriuretic effects of ET-1. CD ETA and ETB receptors do not fully account for the antihypertensive and natriuretic effects of CD-derived ET-1, suggesting paracrine effects of this peptide.

Self-monitoring of home blood pressure with estimation of daily salt intake using a new electrical device

We investigated a simple device to monitor daily salt intake at home and examined the relationship between salt excretion and morning blood pressure in order to enable patients to better manage daily salt intake and hypertension. The correlation between 24-h urinary salt excretion and measured value with salt monitor from overnight urine was significant (n = 224, r = 0.72, P < 0.001). A total of 46 volunteers participated for more than 3 weeks by measuring daily salt intake and morning blood pressure. The relationship between predicted daily salt excretion and blood pressure was examined with use of 3-day moving average. Mean salt excretion and systolic blood pressure (SBP) significantly decreased by the end of the trial (i.e., salt excretion decreased from 158+/-31 to 149+/-30 mmol/day and SBP from 137+/-17 to 133+/-16 mm Hg). Of 46 participants, 18 (39%) had a significant correlation between predicted daily salt excretion and blood pressure (r > 0.4, P < 0.05, n > 21), indicating sodium sensitivity. An additional 17% had a positive correlation that did not reach statistical significance (0.2 < r < or = 0.4), and the remaining 44% had no correlation (r < or = 0.2). Mean decrease in blood pressure per decrease in salt (g) (17 mmol) intake in the 18 participants with a significant correlation was 3.3 mm Hg (SBP) and 1.5 mm Hg (diastolic blood pressure), which was higher than that reported for other studies. Hypertensive patients not using medication showed the largest decrease. We conclude that daily monitoring of salt intake and morning blood pressure will be useful for management of hypertension.

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

OBJECTIVE

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

DESIGN

Cross-sectional population surveys on cardiovascular risk factors.

SETTING

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

SUBJECTS

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

INTERVENTIONS

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

RESULTS

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

CONCLUSIONS

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

SPONSORSHIP

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

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

The role of dietary cations in the blood pressure of renal transplant recipients

BACKGROUND

The role of dietary cations in hypertension has been evaluated in the general population and selected subgroups, but its contribution to blood pressure (BP) elevations in patients with functional renal allografts has not been critically examined.

METHODS

After counseling based on Dietary Approaches to Stop Hypertension (DASH) guidelines, we measured timed 24-h urine excretion rates of sodium, potassium, calcium, and magnesium as a surrogate for their dietary intake, in 244 stable adult single-organ renal transplant recipients, correlating these with averaged blinded clinic-measured BP values. Multiple linear regression analysis adjusting for factors affecting BP in transplant recipients was performed.

RESULTS

There was no correlation between systolic (SBP) or diastolic pressure (DBP) and 24-h urine excretion rates of each cation. There was no BP difference between patients receiving cyclosporine and tacrolimus (127/77 vs. 129/78 mmHg, p = 0.38), or in cation excretion except for calcium (2.85 +/- 2.0 vs. 2.90 +/- 2.8, p = 0.002). Protein excretion (p < 0.0001), age (p = 0.002), and weight (p = 0.04) were positively associated with SBP, while only weight (p = 0.01) was associated with DBP by multivariate analysis.

CONCLUSION

Dietary cation intake is not significantly associated with BP in renal transplant recipients. These data do not support recommendations to alter dietary cation intake as part of the management of post-transplantation hypertension.

Renal functional deterioration is not affected by the magnitude of sodium consumption in a normotensive model of moderate renal failure

BACKGROUND/AIMS

High sodium consumption has been repeatedly reported to exert deleterious effects on severe chronic renal failure progression, mainly via glomerular mechanisms. However, the role of high sodium intake in renal function deterioration in a model of moderate chronic tubulointerstitial disease has not yet been addressed. We evaluated the effects of exaggerated dietary sodium and the resultant increase in proteinuria on renal function deterioration in experimental tubulointerstitial disease in rats.

METHODS

In 48 Sprague-Dawley rats, moderate renal failure (approximately 50% of normal glomerular filtration rate) was induced by administration of lithium chloride in drinking water. The animals were divided into three groups fed low (<0.2% Na(+)), normal (0.5% Na(+)), or high (8% Na(+)) sodium diets.

RESULTS

Animals in all groups remained normotensive with a similar course of GFR downslope and 100% survival, irrespective of sodium regimen. Rats consuming high sodium diets developed significantly greater proteinuria compared to their counterparts fed normal or low sodium chow.

CONCLUSIONS

(1) Deterioration of renal function in a lithium-induced model of normotensive moderate chronic renal failure was not affected by dietary sodium. (2) Unlike in some other human or experimental renal failure models, the magnitude of proteinuria had no adverse effect on the progression of renal deterioration.

Patients with severe bowel malabsorption do not have changes in iodine status

OBJECTIVE

We evaluated the influence of intestinal malabsorption on iodine status in patients who had short gut syndrome and received total parenteral nutrition (group I) compared with control subjects who had eutrophia (group II) and patients who had other illnesses but normal digestive tracts (group III).

METHODS

Twenty-seven subjects were studied. Iodine intake was determined by the measurement of iodine in ingested food and in parenteral nutrition solutions. Urinary iodine excretion was measured by the Sandell-Kalthoff reaction. Urinary creatinine, anthropometric, and thyroid hormone functions were also determined.

RESULTS

Daily iodine intakes were 658 +/- 125 (mean +/- standard deviation), 573 +/- 204, and 629 +/- 208 microg for groups I, II, and III, respectively. Daily urinary iodine excretion levels were 399 +/- 308, 439 +/- 192, and 370 +/- 268 microg and ratios of urinary iodine (micrograms) to creatinine (grams) were 614 +/- 349, 354 +/- 142, and 483 +/- 292, respectively. There were no statistically significant differences across groups.

CONCLUSION

In Brazil the iodine provided by food, including iodized salt, has been sufficient to maintain iodine status in patients with short gut syndrome.

Antibody to marinobufagenin lowers blood pressure in pregnant rats on a high NaCl intake

OBJECTIVE

The pathogenesis of pre-eclampsia (PE), a major cause of maternal and fetal mortality, is not fully understood. Digitalis-like sodium pump ligands (SPLs) are believed to be implicated in PE, as illustrated by clinical observations that DIGIBIND, a digoxin antibody that binds SPLs, lowers blood pressure (BP) in PE. We recently reported that plasma levels of marinobufagenin (MBG), a vasoconstrictor SPL, are increased four-fold in patients with PE. In the present study, we tested whether a polyclonal antibody to MBG can lower BP in rats with pregnancy-associated hypertension.

METHODS

Systolic BP (SBP), 24-h renal excretion of MBG and endogenous ouabain (EO), and sodium pump activity in the thoracic aortae were measured in virgin and pregnant Sprague-Dawley rats without and with NaCl supplementation (drinking 1.8% NaCl solution).

RESULTS

NaCl supplementation of virgin rats stimulated renal excretion of MBG by 60%, but not that of EO, and did not change the BP. Compared with virgin rats, the last week of pregnancy in non-NaCl-loaded rats was associated with a decrease in SBP (106 +/- 2 versus 117 +/- 2 mmHg); a moderate increase in renal excretion of MBG (97.6 +/- 4.9 versus 57.4 +/- 7.0 pmoles/24 h) and EO (36.2 +/- 4.3 versus 24.1 +/- 3.2 pmoles/24 h). NaCl-loaded pregnant rats exhibited elevation in SBP (139 +/- 3 mmHg; P < 0.01 versus non-NaCl-loaded pregnant rats), in renal excretion of MBG (160.0 +/- 17.5 pmoles/24 h; P < 0.01 versus non-NaCl-loaded pregnant rats), but not in EO, and showed fetal growth retardation. Administration of the anti-MBG antibody to NaCl-loaded pregnant rats lowered SBP (111 +/- 2 mmHg; P < 0.01) and increased aortic sodium pump activity (144 +/- 3 versus 113 +/- 5 nmol Rb/g per min; P < 0.01 versus non-NaCl-loaded pregnant rats).

CONCLUSIONS

These observations provide evidence that MBG contributes to BP elevation in pregnant rats rendered hypertensive by NaCl supplementation.

Sodium-Facilitated Hypervolemia, Endurance Performance, and Thermoregulation

The purpose of this study was to investigate the effects of an immediate pre-exercise, orally ingested, sodium load (164 mEq Na+) (IPOSL), equivalent to 10 ml per kilogram of body weight, on plasma volume, endurance performance, and thermoregulation. Fourteen male participants consumed a nearly isotonic (255 mOsm . kg (-1)) IPOSL and a hypotonic (94 mOsm . kg (-1)), no-sodium, placebo beverage (Pl) equivalent to 10 ml . kg (-1) body weight in a randomized design. Subjects cycled at 70 % of maximal work rate, in a 21.0 - 23.3 degrees C lab, for 45 min while cardiovascular and thermoregulatory variables were measured. This was followed by a 15-min performance time trial. IPOSL and Pl ingestion lead to a 3.1 % expansion and a 4.7 % reduction in resting baseline plasma volume, respectively. IPOSL maintained plasma volume during exercise to a greater extent than the Pl at 15 and 30, but not 45 min. There was a significant improvement ( approximately 7.8 %; p < 0.05) in time trial performance following IPOSL. No significant differences were observed for heart rate, core temperature, rate of perceived exertion or total body sweat rate (p > 0.05). In conclusion, IPOSL ingestion increased pre-exercise plasma volumes, maintained 15- and 30-min exercise plasma volumes, and improved an endurance performance time trial better than the Pl with no apparent compromise in thermoregulation.

Iodine nutritional status of adults during a period of salt iodization

BACKGROUND

To measure the iodine nutritional status of island adults in Zhoushan, China.

METHODS

A comparison study was carried out in eight villages. These were selected from iodized salt and non-iodized salt districts of Zhoushan island by random sampling. The Mann-Whitney test was used to compare the urinary iodine concentration and dietary iodine intake between the two districts.

RESULTS

The median of urinary iodine concentration in the non-iodized salt group was 90 micrograms/l, which was lower than 194 micrograms/l in the iodized salt group (u = 14.673; p < 0.000), whereas the median of daily dietary iodine intake in the two groups was 128 and 147 micrograms, respectively (u = 1.847; p = 0.065). There was no significant correlation between dietary iodine intake and urinary iodine concentration (p = 0.095).

CONCLUSIONS

Salt iodization is necessary. Special characteristics of the island diet should also be considered.

Iodine deficiency in Papua New Guinea (sub-clinical iodine deficiency and salt iodization in the highlands of Papua New Guinea)

Data on the status about iodine nutrition in children in Papua New Guinea (PNG) are scarce. This study attempts to determine the mean daily per capita consumption of salt, the iodine content of salt in the households and retail shops and the urinary iodine concentration in children (6-12 years) in Hella Region, Southern Highland Province (SHP), PNG. The mean daily consumption of salt was 2.62 +/- 1.29 g. The iodine content of salt was >30 p.p.m. in 95 per cent of households and 100 per cent of retail shops. The median urinary iodine concentration of 48.0 mg/l for all the children indicates moderate iodine deficiency. The median urinary iodine concentrations for the male (67.0 mg/l) and female (44.0 mg/l) children indicate mild and moderate iodine deficiency, respectively. 68.42 per cent of the male and 81.82 per cent of the female children have urinary iodine concentration <100 mg/l, indicating that iodine deficiency is a potential public health problem in the Hella region. These results indicate a need for further assessment of the implementation of the universal salt iodization strategy for the elimination of iodine deficiency in the SHP, PNG.

In vivo stimulation of apical P2 receptors in collecting ducts: evidence for inhibition of sodium reabsorption

In vitro evidence suggests that intraluminal nucleotides, acting on apical P2 receptors, may influence amiloride-sensitive sodium reabsorption in collecting ducts. The present study has assessed this possibility directly in anesthetized rats, by determining the urinary recovery of 22Na relative to that of [14C]inulin (Na/inulin recovery ratio) during in vivo microperfusion of late distal tubules with artificial tubular fluid containing various P2 agonists (all at 1 mM). In animals maintained on a control diet, in which amiloride-sensitive 22Na reabsorption was modest, the poorly hydrolysable, broad-spectrum P2 agonist ATPgammaS had no significant effect on the Na/inulin recovery ratio. In contrast, in rats maintained on a low-sodium diet, in which amiloride-sensitive 22Na reabsorption was considerably enhanced, ATPgammaS caused a significant increase in the Na/inulin recovery ratio (control: 14 +/- 3%; ATPgammaS: 28 +/- 4%; n = 32 pairs; P < 0.001, paired t-test). No change in the Na/inulin recovery ratio was seen in time controls (13 +/- 3 vs. 14 +/- 4%; n = 15 pairs). In subsequent experiments in rats maintained on a low-sodium diet, we used more selective agonists in an attempt to identify the receptor subtype responsible for the effect of ATPgammaS. The P2Y1 agonist 2meSADP, the P2Y2/4 agonists Ap4A and Cp4U, and the P2X agonist BzATP were all without significant effect on the Na/inulin recovery ratio. These findings constitute the first in vivo evidence for a functional role for apical P2 receptors in collecting ducts, but the identity of the receptor subtype(s) involved remains elusive.

Salt intake and Helicobacter pylori infection

BACKGROUND

The chance finding of an association between Helicobacter pylori infection and hypertension and the known relationship between salt intake and blood pressure led us to speculate whether these two environmental factors might be related. A positive relationship between them might suggest that a high-salt diet could in some way facilitate gastric H. pylori infection.

METHODS

We have therefore conducted an ecological study of the national H. pylori infection rates in the EUROGAST study and national salt excretion levels with the INTERSALT project. Ten nations were included in both projects.

RESULTS

Statistically significant correlation between H. pylori infection rates and salt excretion were found in older men and women (r = 0.728 and r = 0.827, respectively) and in younger men (r = 0.728), but not younger women (r = 0.519).

CONCLUSIONS

Our findings raise the possibility that salt intake may in some way facilitate H. pylori infection. A dedicated population survey is now justifiable to investigate the role of salt intake in H. pylori infection with the measurement of all possible confounding variables including particularly socio-economic status

What factors are associated with high plasma B-type natriuretic peptide levels in a general Japanese population?

There are few community-based epidemiologic studies that have dealt with risk factors for heart failure in non-Western populations. It has been reported that the measurement of plasma B-type natriuretic peptide (BNP) is useful for detecting patients with asymptomatic heart failure. To clarify the determinants of high plasma BNP level, the association of BNP with cardiovascular risk factors in community dwelling residents was examined. The plasma BNP levels were measured in 686 residents aged 35-69 years who received annual health check-up. The relationship of BNP to blood pressure, blood haemoglobin, serum cholesterol (total and high-density lipoprotein cholesterol), plasma glucose, electrocardiographic (ECG) findings, urinary salt excretion, and lifestyle factors (smoking and alcohol consumption) were cross-sectionally analysed. The plasma BNP geometric mean was 13.7 pg/ml. Both linear and logistic regression analyses indicated that the plasma BNP levels were positively associated with age, urinary salt excretion, higher blood pressure, high R-wave voltage in the 12-lead ECG (Minnesota Code 3-1 or 3-3), and female gender. Plasma BNP levels were inversely associated with blood haemoglobin levels. Gender-specific analysis showed similar results. However, plasma BNP did not correlate with other cardiovascular risk factors such as serum lipids.

Collecting duct-specific knockout of endothelin-1 causes hypertension and sodium retention

In vitro studies suggest that collecting duct-derived (CD-derived) endothelin-1 (ET-1) can regulate renal Na reabsorption; however, the physiologic role of CD-derived ET-1 is unknown. Consequently, the physiologic effect of selective disruption of the ET-1 gene in the CD of mice was determined. Mice heterozygous for aquaporin2 promoter Cre recombinase and homozygous for loxP-flanked exon 2 of the ET-1 gene (called CD-specific KO of ET-1 [CD ET-1 KO] mice) were generated. These animals had no CD ET-1 mRNA and had reduced urinary ET-1 excretion. CD ET-1 KO mice on a normal Na diet were hypertensive, while body weight, Na excretion, urinary aldosterone excretion, and plasma renin activity were unchanged. CD ET-1 KO mice on a high-Na diet had worsened hypertension, reduced urinary Na excretion, and excessive weight gain, but showed no differences between aldosterone excretion and plasma renin activity. Amiloride or furosemide reduced BP in CD ET-1 KO mice on a normal or high-Na diet and prevented excessive Na retention in salt-loaded CD ET-1 KO mice. These studies indicate that CD-derived ET-1 is an important physiologic regulator of renal Na excretion and systemic BP.

Relationship between the Awareness of Salt Restriction and the Actual Salt Intake in Hypertensive Patients

A 24-h home urine collection was conducted to estimate accurate salt intake in hypertensive outpatients. Using 24-h urinary creatinine excretion as a criterion for success, urine samples were obtained from 534 hypertensive patients. The urinary salt excretion of hypertensive outpatients ranged widely from 1.5 to 23.4 g/day (mean value 9.7 +/- 3.9 g/day). Urinary salt excretion was higher in males than in females (10.6 +/- 4.0 vs. 9.2 +/- 3.7 g/day, p<0.01). Based on the questionnaires, the patients were divided into salt-conscious patients, or those who were careful to reduce their daily salt intake, and non-salt-conscious patients. It was found that urinary salt excretion was lower in the salt-conscious group than in the non-salt-conscious group (9.4 +/- 3.8 vs. 10.6 +/- 4.0 g/day, p<0.01), but that urinary salt excretion adjusted for body weight was not significantly different between the two groups (0.16 +/- 0.06 vs. 0.17 +/- 0.07 g/kg/day). Our results suggest that there was no obvious reduction in the actual salt intake in salt-conscious patients, suggesting the importance of monitoring salt intake by 24-h home urine collection and informing patients of their actual salt intake as a means of encouraging the achievement of salt restriction.

Dual renin???angiotensin system blockade restores blood pressure???renin dependency in individuals with low renin concentrations

BACKGROUND

The prevailing sodium intake and renin-angiotensin system status influence the blood pressure response to an angiotensin II type 1 (AT1) receptor antagonist or an angiotensin I converting enzyme inhibitor, which is known to be reinforced by a low sodium intake or administration of a diuretic.

OBJECTIVE

To investigate the possibility that combining both drugs might be more effective in conditions of high sodium intake than blocking the renin-angiotensin system in a single step.

METHODS

In a placebo-controlled, four-period crossover study in 12 normotensive volunteers who received a high sodium chloride intake (more than 250 mmol/day for 6 days), the haemodynamic and renin effects of a single oral dose of irbesartan 150 mg combined with fosinopril 20 mg were compared with those of a usual daily dose of fosinopril (20 mg) and a high dose of irbesartan (300 mg).

RESULTS

The changes in blood pressure induced by fosinopril and irbesartan alone were not different from those of placebo, whereas the combination significantly decreased blood pressure. Simultaneously, it increased plasma active renin and prorenin concentrations to a greater extent than did each single-site blocker.

CONCLUSION

In low-renin conditions, combined renin-angiotensin system blockade enables the demonstration of a persistent renin-dependency of the blood pressure. Through its more efficient blockade of the renin-angiotensin system, demonstrated by the increase in renin and prorenin, combined renin-angiotensin system blockade is more effective than doubling the usual dose of an AT1 receptor antagonist. This may offer an alternative strategy for treating patients with a range of renin concentrations, and may potentially increase the cardio- and nephrotective benefits through a more complete blockade of the renin-angiotensin system.

Elevated dietary salt suppresses renin secretion but not thirst evoked by arterial hypotension in rats

Increased dietary salt intake was used as a nonpharmacological tool to blunt hypotension-induced increases in plasma renin activity (PRA) in order to evaluate the contribution of the renin-angiotensin system (RAS) to hypotension-induced thirst. Rats were maintained on 8% NaCl (high) or 1% NaCl (standard) diet for at least 2 wk, and then arterial hypotension was produced by administration of the arteriolar vasodilator diazoxide. Despite marked reductions in PRA, rats maintained on the high-salt diet drank similar amounts of water, displayed similar latencies to drink, and had similar degrees of hypotension compared with rats maintained on the standard diet. Furthermore, blockade of ANG II production by an intravenous infusion of the angiotensin-converting enzyme inhibitor captopril attenuated the hypotension-induced water intake similarly in rats fed standard and high-salt diet. Additional experiments showed that increases in dietary salt did not alter thirst stimulated by the acetylcholine agonist carbachol administered into the lateral ventricle; however, increases in dietary salt did enhance thirst evoked by central ANG II. Collectively, the present findings suggest that hypotension-evoked thirst in rats fed a high-salt diet is dependent on the peripheral RAS despite marked reductions in PRA.

Salt-sensitivity of blood pressure and decreased 11beta-hydroxysteroid dehydrogenase type 2 activity after renal transplantation

BACKGROUND

High blood pressure (BP) predicts a poor long-term kidney graft outcome. The mechanisms for hypertension in renal graft recipients are only partly understood. There is evidence that BP is salt dependent in renal transplant recipients. We hypothesize that renal transplantation induces salt sensitivity by decreasing 11beta-hydroxysteroid dehydrogenase type 2 (11betaHSD2) activity.

METHODS

A syngenic uninephrectomized rat transplantation model (Lewis to Lewis) (n=7) was used to demonstrate salt sensitivity after transplantation. Sham-operated (n=5) and denervated rats (n=5) were used as controls. In all rats, BP was measured continuously by telemetry 24 hr a day, whereas the rats were set successively on a normal- (0.45% NaCl), high- (8% NaCl), low- (0.1% NaCl), and, again, normal-salt (0.45% NaCl) diet during a 6-day period to assess salt-related changes in mean arterial pressure (MAP). 11betaHSD2 activity was assessed by determining the ratio of corticosterone to dehydrocorticosterone metabolites (THB+5alphaTHB)/THA in urine.

RESULTS

After uninephrectomy and implantation of the telemetry device, MAP was comparable in rats assigned to undergo sham operation (100+/-3 mmHg), denervation (105+/-5 mmHg), or transplantation (102+/-6 mmHg). When animals were switched from the normal- to high-salt diet, the increase in MAP was more pronounced in the transplanted group (13.9+/-5.1 mmHg) than in those undergoing sham operation (5.1+/-1.7 mmHg, P<0.004) or denervation (7.1+/-1.8 mmHg, P<0.021). Urinary (THB+5alphaTHB)/THA increased more than 2-fold in the transplanted rats but remained stable in the sham-operated and denervated animals (P<0.0001), indicating reduced activity of 11betaHSD2.

CONCLUSION

Syngenic renal transplantation causes salt sensitivity with increased BP associated with a reduced activity of 11betaHSD2.

A simple method to estimate populational 24-h urinary sodium and potassium excretion using a casual urine specimen

In order to estimate the salt and potassium intake in a population and to compare their annual trends, we developed a simple method to estimate population mean levels of 24-h urinary sodium (24HUNaV) and potassium (24HUKV) excretion from spot urine specimens collected at any time. Using 591 Japanese data items from the INTERSALT study as a gold standard, we developed formulas to estimate 24-h urinary creatinine (24HUCrV), 24HUNaV and 24HUKV using both spot and 24-h urine collection samples. To examine the accuracy of the formulas, we applied these equations to 513 external manual workers. The obtained formulas were as follows: (1) PRCr (mg/day) = -2.04 x age + 14.89 x weight (kg) + 16.14 x height (cm) -2244.45; (2) estimated 24HUNaV (mEq/day) = 21.98 x XNa (0.392); (3) estimated 24HUKV (mEq/day) = 7.59 x XK(0.431); where PRCr = predicted value of 24HUCr, SUNa = Na concentration in the spot voiding urine, SUK = K concentration in the spot voiding urine, SUCr = creatinine concentration in the spot voiding urine, XNa (or XK) = SUNa (or SUK)/SUCr x PRCr. In the external group, there was a significant but small difference between the estimated and measured values in sodium (24.0 mmol/day) and potassium (3.8 mmol/day) excretion. In every quintile divided by the estimated 24HUNaV or 24HUKV, the measured values were parallel to the estimated values. In conclusion, although this method is not suitable for estimating individual Na and K excretion, these formulas are considered useful for estimating population mean levels of 24-h Na and K excretion, and are available for comparing different populations, as well as indicating annual trends of a particular population.

A simple method to estimate populational 24-h urinary sodium and potassium excretion using a casual urine specimen

In order to estimate the salt and potassium intake in a population and to compare their annual trends, we developed a simple method to estimate population mean levels of 24-h urinary sodium (24HUNaV) and potassium (24HUKV) excretion from spot urine specimens collected at any time. Using 591 Japanese data items from the INTERSALT study as a gold standard, we developed formulas to estimate 24-h urinary creatinine (24HUCrV), 24HUNaV and 24HUKV using both spot and 24-h urine collection samples. To examine the accuracy of the formulas, we applied these equations to 513 external manual workers. The obtained formulas were as follows: (1) PRCr (mg/day) = -2.04 x age + 14.89 x weight (kg) + 16.14 x height (cm) -2244.45; (2) estimated 24HUNaV (mEq/day) = 21.98 x XNa (0.392); (3) estimated 24HUKV (mEq/day) = 7.59 x XK(0.431); where PRCr = predicted value of 24HUCr, SUNa = Na concentration in the spot voiding urine, SUK = K concentration in the spot voiding urine, SUCr = creatinine concentration in the spot voiding urine, XNa (or XK) = SUNa (or SUK)/SUCr x PRCr. In the external group, there was a significant but small difference between the estimated and measured values in sodium (24.0 mmol/day) and potassium (3.8 mmol/day) excretion. In every quintile divided by the estimated 24HUNaV or 24HUKV, the measured values were parallel to the estimated values. In conclusion, although this method is not suitable for estimating individual Na and K excretion, these formulas are considered useful for estimating population mean levels of 24-h Na and K excretion, and are available for comparing different populations, as well as indicating annual trends of a particular population.