How does adherence to the DASH diet influence blood pressure?

Scientists have reviewed the available literature to investigate whether the level of adherence to the Dietary Approaches to Stop Hypertension (DASH) diet influences blood pressure. This meta-analysis is available in Metabolites.

Background

Hypertension is a condition associated with steady high pressure of blood flow within vessels. It has been correlated with the incidence of kidney disorders and is one of the leading causes of cardiovascular events and all-cause mortality worldwide.

The current high prevalence of hypertension across the global population is attributed to an elevated elderly population, obesity, sodium-rich diet, and smoking. Recent studies have revealed that besides the use of anti-hypertensive drugs, lifestyle modification can help manage this condition.

These modifications include a low-salt diet, regular exercise, and restricted use of alcohol and cigarettes. In the context of optimal diet, the Dietary Approaches to Stop Hypertension (DASH) diet has been designed to maintain normal blood pressure. A DASH diet contains an abundance of vegetables, fruits, low-fat dairy products, and fiber.

It is important to adhere to the DASH diet to achieve beneficial effects. The DASH Score has been designed to assess the level of adherence to the DASH diet. This scoring system is based on information from validated food frequency questionnaires. A high or low DASH score indicates the level of adherence to the diet.

About the study

Although many observational studies have assessed the effect of the DASH diet on cardiovascular events, these studies have presented contradictory results. Keeping these contradictions in mind, a recent study conducted a systematic review and performed a meta-analysis to assess how different adherence levels to the DASH diet influence blood pressure values.

For this systematic review and meta-analysis, all relevant articles were obtained from electronic databases, such as Web of Science Core Collection, Scopus, and PubMed, from inception to November 2022. Studies published only in English were considered.

Study findings

A total of 4,319 citations surfaced after the initial search. After removing duplicates and considering the eligibility criteria, 37 observational and interventional studies were considered in this systematic review and meta-analysis. Among these 37 studies, 20 were cohort studies, 14 were cross-sectional studies, 3 were randomized control trials (RCTs), and 1 was a case–control study.

High heterogeneity was observed in the published articles. These studies presented differential systolic blood pressure (SBP) and diastolic blood pressure (DBP) values between participants in the highest and lowest adherence group.

After reviewing the articles thoroughly, the current review indicates that higher adherence to the DASH diet promotes a favorable effect on SBP. It must be noted that only a few studies have mentioned the prevalence of SBP > 140 mmHg in individuals who adhered to the DASH diet. 

The majority of individuals with high levels of DASH diet adherence presented a mean DBP < 130 mmHg. Interestingly, these studies also support the fact that high adherence to the DASH diet causes a reduction in DBP values in subjects with normal DBP. 

A previous meta-analysis revealed that compared to the usual diet group, the DASH diet caused a reduction in both SBP and DBP. Importantly, the DASH diet substantially reduces the levels of cardiovascular disease risk factors, such as total and low-density lipoprotein (LDL) cholesterols. Furthermore, adherence to this diet caused a reduction in obesity, HbA1c levels, and insulin concentrations. 

Dietary adherence is dependent on an individual’s preference, socioeconomic status, level of education, place of residence, medical history, and religion. In addition, psychological factors and individuals’ behavior also influence the levels of adherence to a diet.

Conclusions

The current study has some limitations that include the consideration of a high number of observational studies, restricting confidence in the findings. In addition, these studies limited the scope to determine the causality between adherence to the DASH diet and blood pressure outcomes. The high heterogeneity of the included studies could affect the findings.

The authors claimed this systematic review and meta-analysis to be the first to assess the association between adherence to the DASH diet and blood pressure levels. A higher adherence to the DASH diet lowered the incidence of hypertension compared to lower adherence.

In addition, greater adherence to the DASH diet prevents the development of type 2 diabetes mellitus and cardiovascular diseases (e.g., coronary heart disease and stroke). It also significantly reduces all-cause, cancer, and CVD mortality.