| PrefaceHypertension is a kind of disease that seriously threatens people's health and it is one of important risk factors that induce cardiovascular and cerebrovas-cular disease. Reducing the blood pressure levels of population can not only control the incidence of cardiovascular and cerebrovascular disease effectively, but also reduce the mortality of them. To the definitive people that have got hypertension and the high - risk group of cardiovascular and cerebrovascular disease , the measures of using drugs reduce blood pressure have been proven an effective method. While useful, pharmacologic treatments of hypertension is not a panacea for prevention of the burden of illness resulting from high BP. Increasing evidence indicates that nutritional factors may play a fundamental role in the etiology of hypertension and selected nutritional interventions may provide a safe and potentially cost - effective means to prevent and treat high BP.Dietary sodium restriction and (or) potassium supplementation is the core of dietary approaches to stop hypertension. The results of several short — time randomized clinical trials (RCT) have shown that the regulation of dietary sodium and potassium intake can reduce BP. In western countries, the results of RCT that changing the contents of sodium and potassium in salt can decrease BP have been reported. However, No researches of this aspect in the group of hypertension and cardiovascular and cerebrovascular disease in North of China who consume a high sodium and low potassium diet. So we conducted this RCT to test the effect of high - potassium, low - sodium salt - substitute on systolic and diastolic BP among individuals with hypertension or cardiovascular and cerebro-vascular disease in a sample of countryside residents in ZhanWu County, LiaoN-ing Province. Meanwhile, we also evaluate the safety of using salt - substitute.Subjects and methods1. The selection and assignment of subjectsA total of 104 men and women aged 30 to 80 years with hypertension and cardiovascular and cerebrovascular disease were selected from ZhangWu County, LiaoNing Province. The primary eligibility criteria include hypertensive patients whose systolic BP5=160mmHg and cardiovascular and cerebrovascular disease patients that have longer hypertensive history (including stroke , CHD). Each eligible subject must be confirmed by the hospital of county grade or higher -level hospital. The main exclusion criteria include the subjects who have apparent hepatic or renal damage history, or were taking medicine that can keep potassium in the body, or could not adhere the study. All of the study participants were randomly allocated to receive either salt - substitute {65% sodium chloride + 25% potassium chloride +10% magnesium sulphate) or normal salt (100% sodium chloride). Randomization was based on assignments generated by a computer program. All the salt - substitute and normal salt are produced by Beijing Salt Corporation according to the national standard.2. The contents of epidemiological survey and the method of research1) Questionnaires were filled by means of inquiring and measurement in sites. The contents of survey included: general characteristics, previous disease history, medical history, smoking habits, alcohol habits and so on, measurement of the blood pressure, body height, weight and soup taste. The surveys of the baseline were complete in 1 month. BP and weight were measured at every visit phase ( -1, 0, 1, 2, 3, 6, 9 and 12 month). The taste of the soup was evaluated at 1, 1,6, and 12 month after initial intervention.2) The midpiece of first urine samples in the morning were collected at 1, 6 and 12 month , and frozen in aliquots at -10°C until assayed . It was used for the measures of urine sodium and urine potassium.3. The metered methods of indexesBlood pressure was measurement by Omron HEM - 770 electronic sphygmo-manometer according to the unified standard under standard conditions.2) Body height and weight were measured by tape and weighing scale.3) The taste of the soup was measured by visual analogue scale (VAS).4) Urine sodium and urine potassium were measurement by automatic biochemistry analyzer 7600 ( HITACHI, Japan).4. Statistical methodsAll of the data were analyzed with SPSS11. 5. Measurement data were presented as mean values and standard deviation. Numeration data were presented as numbers and percentage. The comparison between two groups will be analyzed using Student^ t — test in Measurement data and Chi - square test in Numeration data. The size of the blood pressure difference and the 95% confidence interval about the effect will be calculated. A two - sided value of P <0. 05 was regarded as statistically significant.Result1. The primary character of salt — substitute group and normal salt group There were no statistical differences ( P > 0. 05 ) of body height , weight,SBP, DBP, urine sodium, urine potassium, smoking habits and alcohol habits, medical history between the two groups,but not age (P <0. 05).2. The changed tendency and reduced differences of BP between salt - substitute group and normal salt group2.1 Comparing the changed tendency of BP between the two groups During treatment BP (SBP and DBP) values changed significantly in bothgroups. They both experienced a process from decrease to upgrade then decreaseagain. At every stage, there were no significantly differences between the BP intwo groups.2. 2 Comparing the reduced difference of BP between the two groups 2.2. 1 General comparisons between the reduced differences in BP of thetwo groupsAt the end of this study, average systolic BP was reduced 22. 51mmHg insalt — substitute group and 12.20mmHg in normal salt group. The corresponding net reduction in systolic BP was 10. 31mmHg for the salt - substitute group compared to the normal salt group ( P <0. 05 ). Average diastolic BP was reduced 12. 18mmHg in salt - substitute group and 6.73mmHg in normal salt group. The corresponding net reduction in diastolic BP was 5.45mmHg for the salt - substitute group compared to the normal salt group (P <0.05).2.2.2 Comparing the reduced differences of BP between the two groups between different age groups<60 years old: The reduced differences of systolic BP and diastolic BP were all no statistical significance at every stage of the study. ^60 years old;At the end of study, average systolic BP was reduced 29. 05mmHg in salt - substitute group and 10. 91mmHg in normal salt group. The corresponding net reduction in systolic BP was 18. 15mmHg for the salt - substitute group compared to the normal salt group (P <0.05). Average diastolic BP was reduced 17.29mmHg in salt —substitute group and 6.43mmHg in normal salt group. The corresponding net reduction in diastolic BP was 10. 86mmHg for the salt - substitute group compared to the normal salt group ( P <0. 05).3. Comparing the changes of soup taste between salt - substitute group and normal salt groupAt baseline, there were no significant differences in saltiness, flavour and acceptability of the soup between the two groups. At randomised stage, there were significant differences in acceptability of the soup between the two groups. The score of salt — substitute group was higher than normal salt group. At the 6th month of the visit, there were significant differences in flavour of the soup between the two groups. The score of salt — substitute group was higher than normal salt group. At the end of the study, there was no statistical significance again in saltiness, flavour and acceptability of the soup between the two groups.4. Comparing the changes of urine sodium and urine potassium between salt - substitute group and normal salt groupFrom baseline to the two follow - up visits, there was no statistical significance in measurement of urine sodium. At the 6th month of the visit, the measurement of urine potassium in salt - substitute group was higher normal saltgroup (P < 0. 01 ). There was no statistical significance again between the two groups at other stage of the visit.5. Serious adverse events (SAE)During the study, six persons have happened SAE. There were two persons in salt - substitute group and four persons in normal salt group. Comparison between the two groups, there were no statistical significance.6. Loss to follow upAll of the subjects in salt — substitute group completed the study, there was one person in normal salt group quit the study at the 6th month of the visit.Discussion1. The changed tendency of BP between salt - substitute group and normal salt groupThe BP of two groups both experienced a process from decrease to upgrade then decrease again in this study. It may be contributed to a change in ambient temperature following the changes in seasons during the intervention. The negative influence of temperature on BP is well documented. This study began on summer, and after experienced a winter, then ended on next summer. So the ambient temperature were also experienced a process form high to low then high again. High temperature had a hypotensive effect resulting from two different heat - induced mechanisms;a decrease in cardiac output arising from depletion of the plasma volume secondary to sweating;a decrease in peripheral resistance to blood flow due to vasodilatation. On the contrary, the role and probable mechanisms of low temperature are contrary with it. However all subjects taking part in the study were subjected to the same environmental conditions;the influence of the change in temperature would thus apply equally in two groups. So the changing tendencies of BP in two groups were same approximately.2. The influence of salt — substitute on blood pressure of patients in hypertensive and cardiovascular and cerebrovascular diseaseThe results of this randomized, double blind, controlled clinical trial show that salt - substitute reduces BP substantially in the group of hypertension andcardiovascular and cerebrovascular disease in North of China after a years intervention. The magnitude of net reduction in systolic BP is 10. 31mmHg and dias-tolic BP is 5.45mmHg. Observational epidemiological studies and clinical trials have demonstrated that increased systolic BP is an important independent risk factor for CHD, stroke, and end - stage renal disease. A moderate reduction in systolic BP at the population level would be expected to produce a substantial reduction in cardiovascular disease ( CVD) mortality and morbidity. For example, data from the Multiple Risk Factor Intervention Trial (MRFIT) screening cohort indicate that a 5mmHg lower level of systolic BP is associated with a 10. 5% reduction in CHD mortality, a 15. 5% reduction in stroke mortality, a 11.3% reduction in CVD mortality, and a 7.9% reduction in all -cause mortality. So the result of this trial indicates that the use of salt - substitute might provide an effective means to reduce BP in the group of hypertension and cardiovascular and cerebrovascular disease in North of China, and then reduce mortality and morbidity of them.Several factors could have contributed to the effect that salt - substitute reduced BP. Firstly, the content of sodium in the salt - substitute in this study was decreased by 35 percent. Under the conditions that subject didnt change their dietary habits, the amount of their salt intake per day were also decreased by 35 percent. The amount of salt intake in the Northern population of China is 20 g per day on the basis of findings in the past. So the amount of salt intake in subjects of this study was decreased by 7 g per day equivalently. Law et al. analyzed seventy - eight trials with regard to salt reduction applying Meta - analysis method. The results indicated if salt intake was reduced 3g per day, systolic BP would be decreased 5mmHg average after several weeks. According to the results of Law, the systolic BP and diastolic BP of subjects in this trial would be decreased 11.7mmHg and 5. 8mmHg respectively. It is proximal with the results of this trial. Secondly, there are 25 percent potassium chlorides in the content of the salt - substitute. The supplement of potassium can also reduce BP. Many of the trials, epidemiological and clinical studies have demonstrated that BP is lower in the population who have higher potassium intake. The increase of potassium intake can reduce BP in normotensive and hypertensive population. Thestudy of INTERSALT proved that potassium is an important factor to influence BP. Its role is independent and the direction is contrary to sodium. A meta -analysis reported by Whelton PR demonstrated systolic BP and diastolic BP was reduced 4. 4mmHg and 2. 5mmHg respectively in the hypertensive patients whose potassium supplement exceed to 60mmol per day. It showed the role that potassium supplement to the treatment of hypertension. The subjects of the salt - substitute group in this study, whose salt intake exceed to 60mmol per day, so the effect of BP reduction of theirs should approach to the results of Whelton PR. In addition, the results of many researches have showed interaction between sodium and potassium. The effect of high - potassium, low — sodium dietary on BP is more significant than either alone. For instance, the result of DASH trial discovered low salt diet less than lOOmmol sodium chloride intake per day can reduce BP. If the high - potassium food was intake simultaneously, such as fruits and vegetables and so on, BP will be reduced more significantly.3. The influence of salt - substitute on blood pressure of different aged patients in hypertensive and cardiovascular and cerebrovascular diseaseAge is one of important factors that influences blood, so the comparison stratified according to age between the two groups was performed. The results suggested the effects that salt - substitute reduced BP focus on the older population whose ages have exceeded sixty years. Average systolic BP was net reduced 10. 91mmHg and diastolic BP was net reduced 6.43mmHg. There is substantial evidence that elderly people benefit more from a reduction in sodium intake than young people. It may be related to salt sensitivity of BP. Salt sensitivity was defined that the higher salt intake induces BP rise relatively. Based on the conclusions of the literature, salt sensitivity of BP increased continuously following to the rise of the age. It is more obviously in the hypertensive patients. So the proportion of salt sensitivity is larger in old hypertensive patients than others. The application of the salt - substitute reduced the salt load of patients in older hy-pertesive and cardiovascular and cerebrovascular, and reduced their BP significantly.4. The influence of salt — substitute on urine potassium of patients in hypertensive and cardiovascular and cerebrovascular diseaseThe result of urine sample in the subjects of two groups demonstrated the measurements of urine potassium were in the range of common. No one was in hyperpotassaemia. It showed the application of the salt - substitute was safe. The concentration of kalium ion in urine sample increased at the sixth month of the visit obviously and decreased at the end. of the visit again. The reason may be the metabolism of electrolyte in the body was changed following to the intake of salt - substitute. At present few literatures about this aspect were reported. It needs to be proven in further study.5. The influence of salt - substitute on taste of patients in hypertensive and cardiovascular and cerebrovascular diseaseBertino M et al. researched the influence of long - term low salt diet to the taste of the people. The result demonstrated the individual who have had low salt intake decreased their salty favors to the food. Several other studies showed the favor to some kind of food correlated with salty favors to others foods significantly. The results of this study suggested there was no statistical difference between salt - substitute group and normal salt group in the comparison of the salty favor of the soup after a year's intervention. In other words, there was no obviously change in the salty favors of salt - substitute group. There were others literatures reported the reason of the people changed their salty favors may be the experienced change that the people tasted salty food, instead of physiologic reaction that the people changed their salt intake. In this study, the comparison of two groups in flavor and acceptability were significant differences at begin, and were no significant differences at the end of the study. It suggested salt - substitute was tolerated and acceptable. So it is possible with salt - substitute replaces normal salt.In conclusion, the results of this RCT indicated that salt - substitute lowers systolic BP and diastolic BP in the patients of hypertension and cardiovascular and cerebrovascular disease in North of China, and the application of salt — substitute was safe.The deficiency existed in this study: (1) during the study, we desired subjects keeping their usual eating habits. To these high — risk individuals, they almost took medicines of reducing blood more or less everyday. In spite of nodifferences in the history of taking medicines between the subjects of two groups at baseline, it is difficult to ensure constant coincidences in the course of one -year intervention. So the imbalance in taking medicines between two groups can influence the effects of the trial. (2) This study was a portion of large — scale multi - central trial, so the distributions of age in two groups emerged imbalance. Ages of the subjects in normal salt group were larger than in salt - substitute group. (3) Sample sizes in this study were not enough, so the result of the study can only provide a reference. It requires RCT that have larger sample sizes to verify our results in the future.ConclusionThe results of this study indicated;1. The application of salt - substitute may reduce the BP of hypertensive and cardiovascular and cerebrovascular patients in North of China.2. The application of salt - substitute is safe.
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