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.