The Effect of Green Coffee Consumption on High Blood Pressure

Introduction

Hypertension is a major public health difficulty defined in adults with an average SBP of 140 mmHg or greater and DBP of 90 mmHg or greater. those with an SBP of 130 to 139 mmHg or DBP of 80 to 89 mmHg are regarded as prehypertensive [1]. In the past four decades, the prevalence of hypertension has reduced in high-income countries (HICs), whereas it has increased in low-income countries (LICs) settled in Sub-Saharan Africa and southern Asia [2]. Today, hypertention is regarded as a significant cause of death and disability in developing countries. One-quarter of the world's adult population has hypertension, which is likely to increase to 29% by 2025 [3]. The highest prevalence was observed in countries with good economic status in 2000, but it is estimated that in 2025, the highest prevalence will be in developing continents or in low- and middle-income countries [4]. Each 2 mmHg rise in systolic BP is associated with a 7% increased risk of mortality from ischaemic heart disease and 10% increase in stroke [5].

Coffee is widely available around the world. A large number of in-vitro, epidemiological, animal, and human clinical studies showed that coffee is a functional food and its regular consumption could decrease the risk of cardiovascular diseases, type 2 diabetes mellitus, liver diseases, neurodegenerative diseases, and several cancer types, and their mortality [6]. Sarria et al. showed that systolic and diastolic blood pressure (BP) significantly decreases after green coffee consumption [7]. Revuelta-Iniesta et al. showed that green coffee consumption decreases BP [5].

Green coffee contains a large amount of phytochemicals with potential health effects, including methylxanthines (mostly caffeine), dietary fiber, and minor components such as the diterpenes cafestol and kahweol or trigonelline [8]. However, phenolic compounds are one of the most plenty phytochemicals in coffee, largely hydroxycinnamoyl-quinic acids, also known as chlorogenic acids or caffeoylquinic acids [9]. Several animal and human intervention studies about polyphenol-rich green coffee have shown promising results on body weight, serum glucose, plasma lipids, BP, and vascular function. There is shown that unfiltered coffee with more caffeine increases BP and other endothelial disorders, and its diterpenoids have hyperlipidemic effects [3]. Therefore, green coffee has become popular in recent years. It is rich in chlorogenic acids and has near the same caffeine content (60–72 mg/100 g) as instant coffee. However, it is reported that unprocessed green coffee on average contains 70% more polyphenol components (free and conjugated hydrocinnamic acid) than roasted coffee [10].

There are no conclusive results from clinical trials studing the effects of green coffee on BP. Therefore, the goal of this systematic review was to explore the effects of this functional food on blood pressure in adults.

Materials and Methods

We searched all English language literature published in PubMed-Medline and Scopus Databases. The main search keywords were as follows: ("Blood pressure" OR "Arterial pressure" OR "pulmonary pressure" OR "venous pressure" OR "central venous pressure" OR "portal pressure") AND (" Green coffee"). Inclusion criteria were randomized controlled clinical trials conducted on people aged between 18 and 70 with more than 15 participants. The publication date of articles was from 2004 until 2018. Exclusion criteria were the articles not published in English.

A total of 1485 articles were gathered, of which 20 were duplicates. Titles and abstracts of the remaining articles were checked for their relations to the effect of green coffee consumption on high BP . If the articles were potentially relevant, we regained their full texts (45 papers). After the reviewer determined an article did not meet the eligibility criteria, the article would have been rejected on initial screening. Finally, 35 articles were excluded because they did not include the eligibility criteria. After reading the full texts, ten articles remained. Finally, we discussed five articles (Figure 1). All titles and abstracts were studied by one reviewer, but the assay of the full texts was conducted by a reviews team. Atleast 2 reviewers evaluated the full articles independently.

Moreover, after retrieval of articles from the search, all articles' references were checked for potentially relevant articles. We extracted the sex of participants, age range, amount of green coffee, period of intervention, age range, publication year and country, and systolic blood pressure (SBP) and diastolic blood pressure (DBP) as the outcomes. Quality assessment was assayeded through Cochrane Collaboration's tool, which considers random sequence generation, allocation concealment, blinding of outcome assessment or personnel, incomplete outcome data, selective reporting. The quality of articles is as follows: Good (low risk for more than 2 items), Fair (low risk for 2 items), and Weak (low risk for less than 2 items). Figure 1 shows the flow chart for the study included in the review.

Table 1. of the risk of bias in studies included in the systematic review

Results

We identified 45 articles after the screening of articles based on titles and abstracts. Then we excluded one article in non-English language and five articles which did not address the association between green coffee and BP, and finally, one article was retracted by the journal (Figure 1).

Finally, four articles were selected. The quality of the three final articles was assessed and was categorized as good, and one of them was fair (table 1). Studies which used different doses and duration for intervention led to different results. For example, in a study on postprandial glucose levels, green coffee could not decrease BP after 180 minutes. However, the study done by Martinez Lopez et al., with more follow-up time (8 weeks) and more sample size (52 people) a coffee drink containing 35% green coffee significantly decreased both systolic and DBP. However, in the study by Roshan et al., 400 mg green coffee extract only reduced SBP. Besides,

Revuelta et al. designed a randomized pilot cross-over study with black and green coffee groups for two weeks. They observed that SBP was significantly decreased only after green coffee consumption. In a double-blind, randomized controlled clinical trial, participants with mild essential hypertension received 0.48 g green coffee extract (GCE) mixed with 125 mL/day vegetable and fruit juice. SBP and DBP was reduced after 4-month, but it was not significant. The main difference between this study and the others was that the age of the participants in this study was more than 50 years, while in other studies that shown a decrease in BP, the age of participants was 18 to 45 years.

The characteristics of eligible studies including sex and age of participants, amount of green coffee, period of intervention, publication year, country, and SBP and DBP of participants are provided
in Table 2.

Table 2. Characteristics of eligible studies.

Figure 1. Flowchart of the procedure used to select the relevant articles