4. Discussion
Large number of studies has repeatedly demonstrated that consumption of
the DASH diet could decrease BP in
hypertensives[10,11],but it has been less commonly used in
hypertensive patients with T2D. In the study by Azadbakht et
al.[13], after 8 weeks of DASH diet intervention
among patients with T2D, the intervention group had a significant BP
reduction compared with the control group. Paula et al.[12]also had a similar conclusion, but in the
study of Hashemi et al.[17], there was no
significant difference in the reduction of BP between the DASH diet and
the control diet. To the best of our knowledge, this is the first study
evaluating the effects of DASH eating pattern on BP among Chinese
patients with hypertension and T2D.
We modified the original DASH diet according to the dietary habits of
Chinese people, and formed CM-DASH diet. Participants had high
compliance during the intervention, and no one dropped out because of
diet,which indicated that CM-DASH diet was meets the dietary preferences
of Chinese people.Our study revealed that hypertensive patients with T2D
who followed a CM-DASH diet during an 8-week period had a major
reduction in SBP and DBP. From
baseline to 8 weeks later, the mean SBP had decreased by 14.32 mmHg in
intervention group,10.98mmHg in control group and ,the mean DBP had
decreased by 6.32 mmHg in intervention group,5.24 in control group.The
largest reduction in BP was observed in SBP at the end of week 4,
approximately 18 mmHg in the intervention group, 12mmHg in the control
group.
Sodium reduction was considered to be a factor underlying the
hypotensive effect observed in this study. The baseline mean salt
consumption of participants in this study was 8.94g per day, but with
the CM-DASH diet, the mean salt intake of participants was reduced by
approximately 4g per day. As the golden criteria to determine the intake
of sodium, 24-hour urine electrolyte electrolytes has been widely used
in scientific research[18].Our results shows that
after the intervention of CM-DASH diet, the 24-hour urine
Na+ of the intervention group and the control group
both decreased significantly, which indicated that CM-DASH diet had a
marked effect on reducing the sodium intake of the participants. Studies
have shown that high dietary sodium intake can lead to high BP by
inhibiting the activity of Na + - K+ - ATPase pumps in cell
membrane[19], damaging vascular endothelial
function[20]and activating RAAS
(Renin-Angiotension-Aldosterone System)[21]. There
is substantial evidence that reducing sodium intake lowers BP in persons
with hypertension. We also found similar hypotensive effects in patients
with hypertension and diabetes.
Contrary to the effect of sodium on BP, potassium can lower BP by
stimulating Na + - K + - ATPase
pumps and the opening of potassium channels in vascular smooth muscle
cells and adverse nerve receptors[22].The DASH
diet also recommends reducing dietary sodium and consuming more
potassium-rich fruits and vegetables[9], but it is
hard to achieve the desired effect by supplementing potassium with food.
Studies have shown that increasing potassium intake by consuming low
sodium salt is an effective and economical
way[23]. We used low-sodium salt with a sodium
chloride content of 52% and a potassium chloride content of 31% in the
intervention group, while the control group used common salt with a
sodium chloride content of >99%. Our results showed that
there were significant changes in 24-hour urinary K+and Na+ / K+ ratio in the
intervention group, but not in the control group. Although there is no
significant difference in BP drop between the intervention group and the
control group, we observed that the decrease of SBP in the intervention
group appeared earlier and more significantly than that in the control
group. In view of previous studies[24,25] suggest
that the high level of potassium in the DASH diet is important for its
hypotensive effects,we still consider that the application of low-sodium
salt in the DASH diet may have more beneficial effects on BP reduction
in hypertensive patients with T2DM, and a significant difference may be
found by increasing the intervention time and expanding the sample size.
It was considered that the high potassium content of the low-sodium salt
could result in hyperkalemia and safety monitoring was conducted. During
the study period,
no serious adverse events occurred, and the safety of the participants
was monitored and confirmed throughout the study period. Serum test
results showed that there was a slight increase in potassium during the
intervention period, but it was still within the normal range. In
addition, there is no significant difference in the changes of AST, ALT,
UA, Urea. However, urine UACR and serum creatinine showed a significant
decrease compared with baseline in two groups , which may be related to
the reduced sodium intake in the
CM-DASH
diet. Studies have reported that excessive salt intake is associated not
only with high BP but also target organ
damage[26].There is an association between high
salt intake and UACR independent of BP, and oxidative stress is a
modifying factor between them[27].The research of
Feng J. He et al. showed that with the salt reduction, the urine albumin
and UACR also decreased significantly[28]. In view
of these results, we believe that short-term CM-DASH diet and sodium
reduction feeding trials may have beneficial effects on the improvement
of renal function.
Most evidence for the DASH diet comes from short-term feeding
studies[10,29] or dietary behavioral intervention
studies[30],but both methods were used in this
study. Interestingly, although the dietary and salt requirements for
participants during the dietary behavior intervention were the same as
those during the feeding trial, we still observed a small increase in BP
in phase 3, which was also confirmed by the changes in urine
Na+ and K+ in 24 hours. Cooking
meals that meet dash nutritional requirements at home is affected by
many interference factors, which makes it difficult for participants to
strictly comply with our recommendations. On the other hand, CM-DASH
diet menu contains coarse grains, low-fat milk and nuts, which is
difficult for Chinese people to consume on a regular basis. It will take
longer to change the eating habits of Chinese people that have lasted
for thousands of years. In the future, we should strengthen health
education on diet to change the dietary behavior of Chinese people with
hypertension and T2D.
In conclusion, The results of the present study demonstrated that 52%
low-sodium salt applied to the CM-DASH diet is an effective nutritional
strategy for the control and management of BP in Chinese people with
hypertension and T2D.