2. Materials and Methods
2.1. Participants
\begin{equation} n=2\delta^{2}*f(\alpha,\beta)/(\ u_{1}-u_{2})^{2}\nonumber \\ \end{equation}
Inclusion criteria: (1) aged ≥ 35 and ≤ 75 years; (2) no plan to move out of the community in the next three months; (3) agree to consume the salt and DASH meals we provide during the trial; (4) clinically diagnosed patients with hypertension and T2D,and the SBP is between 130-180mmHg, DBP is between 80-110mmHg (without antihypertensive drugs).Exclusion criteria:(1)serious complications of hypertension or T2D; (2) hypercortisolism or aldosteronism; (3) acute disease, such as upper respiratory infection, fever and diarrhea; (4) patients or family members has abnormal kidney function or use potassium-retaining diuretics; (5) patients or family members have abnormal liver function; (6) pregnant or others who are not suitable to consume low-sodium salt.
The Ethics Committee of CQMU (Chongqing Medical University) has approved the experiments, including any relevant details(20/03/2020) which means that all experiments were performed in accordance with relevant guidelines and regulations,and all participants provided written informed consent before enrollment in the trial.
2.2. Study design
We used a randomized controlled parallel-design. After completing the baseline questionnaire and physical checkup, participants were randomly assigned to intervention group (CM-DASH diet +52% low-sodium salt) or control group (CM-DASH diet +common salt) for 8 weeks with a random number table,and participants do not know which group they are assigned to. The present study is divided into 3 phases(2 weeks of CM-DASH diet adaptation + 2 weeks of CM-DASH diet feeding + 4 weeks of CM-DASH diet behavior intervention), and two dietary intervention methods have been adopted. In phase 1 and phase 3, we designed a 7-day menu of Chinese food that met the nutrient criteria of the DASH diet. At the same time, we also provide salt (52% low sodium salt or common salt), and the participants cooked at home according to the menu we provided .In phase 2, patients are required to consume the CM-DASH diet provided by us at a uniform location. All participants were told not to change their previous exercise habits and drug use during the intervention.
Participants were followed up in the hospital once a week to collect information on OBP, salt and drug use. In addition, for trial safety, patients were examined at baseline, 4 weeks after the intervention and the end of the trial.
2.3. CM-DASH
We have developed a modified DASH diet that we called CM-DASH. CM-DASH is tailor-made according to Chinese dietary habits, with the same nutritional content as the original DASH diet, and is generally better accepted by Chinese people.The general requirements of food selection are as follows: rice is the staple food mixed with coarse grains;white meat (chicken and fish) accounts for the majority of meat;low-fat milk is used; more green leafy vegetables and fruits with low sugar;moderate intake of nuts;daily cooking oil(plant oil) < 30g and salt < 5g. Compared to the original DASH diet, the modified diet contains less total fat,saturated fatty acids and calories.The CM-DASH diet for one person is shown in Table 1.
2.4. Salt
In this study, 52% low sodium salt of ”Gu Da Chu” was developed by Shanghai Institute of Ecological Health Sciences. Name: solid compound condiment, standard of execution: Q/BAAM0009S, food production license number: SC10334042205441, and the main ingredients include potassium chloride (31%), sodium chloride (52%). Common salt of ”Jing Xin” was developed by Chongqing salt industry group Co., Ltd. Name: purified salt, product standard: NY/T1040, and the content of sodium chloride content>99%. In Phase 1 and Phase 3, we used 52% low-sodium salt or common salt to completely replace the salt in the participants’ homes,and we also provided a quantitative pot and a quantitative spoon to allow participants to control the amount of salt used in the family(<5g per person per day). In addition, we use an electronic scale(Precision:0.1g) to weigh the salt consumption every week , and estimate the daily salt consumption of each person according to the family population.
2.5. Blood pressure measurement
Participants were followed up in the hospital once a week to collect information on OBP. OBP was measured by trained professionals, and 3 measurements was required to be completed between 8-9 am, interval of about 2 min,and the average of the last two BP measurements was used for analysis. The BP measuring instrument adopt validated automated upper-arm cuff devices that operate through the oscillometric technique (Manufacturer:Omron,Dalian,Co.,Ltd. Product name:“Omron” electronic sphygmomanometer. Model: HEM-7130).
2.6. Laboratory Measurements
Laboratory measurements included 24-hour urinary electrolytes, blood electrolytes, blood lipids, liver function, renal function, urinary creatinine and urinary albumin. All indexes were tested in the Second Affiliated Hospital of CQMU, and we reported the results to patients in a timely manner.
2.7. Statistical analysis
Statistical analysis was carried out using SPSS 24.0 (IBM, Armonk, NY, USA). Quantitative normal distribution data was described by mean and standard deviation, and T test was used to compare the difference between the intervention group and the control group. Qualitative data is described by frequency, and the Pearson’s chi-square test is used to compare the differences between groups. Non-positive distribution data are expressed in median and quartiles, and Friedman’s Rank Test was used. Repeated measures analysis of variance (RMANOVA) was used to analyze the changes of physical examination indexes during the intervention.The Generalized Estimating Equation (GEE) was used to compare the changes in blood pressure during each week, and Bonferroni method was used for comparison between groups. P values <0.05 were considered statistically significant.