Caffeine for life

 

    This study was conducted as a secondary data analysis, by reviewing more than 35 published research articles related to caffeine consumption and blood parameters fluctuations. The main focus of this study was to identify the effect of caffeine consumption on blood pressure and heart rate. The effect was monitored as short time caffeine consumption and the long time caffeine consumption effects.

Introduction 

 

    Caffeine is a psychoactive compound which can be found in many food sources such as coffee, tea, cocoa containing food products, sports drinks, carbonated beverages, and some drug medications. Within these sources, coffee is one of the main sources which contains a considerable amount of caffeine and different coffee products contain different amount of caffeine (Butt et al., 2011). It is estimated that caffeine intake of 400 mg per day is not associated with adverse effects like toxicity, cardiovascular events, effects on bone health and calcium balance, behavior changes, cancer incidents and effects on male fertility but more than 400 mg of caffeine per day may be toxic to some individuals. Because of that, investigate the effect of caffeine on blood pressure and heart rate is important.

    Dietary patterns and lifestyle factors are different among people in different regions of the world. Environmental factors, economic status, and population are some of the reasons for these variations and due to that, blood pressure and heart rate patterns are different between people in different regions of the world. Global coffee production and the distribution is different from region to region such as Brazil has the highest coffee production and according to the International Coffee Organization, International coffee council 112th session, Asia and Europe has the highest coffee consumption rate. But the majority of researches on caffeine and blood pressure have been conducted in western regional countries and it is not accurate to totally depend on another regional study results. Because of that, to see the effect of dietary pattern on blood pressure and heart rate accurately, regional studies should be considered.

    Blood pressure is one of the most widely recorded physiological functions of the body. It measures the pressure fluctuations in the arterial system and indicates the present cardiovascular function as well as risk for future cardiovascular problems (Sherwood & Carels, 2010). Different techniques are using in the hospital setup to measure blood pressure and those methods have their own strengths and limitations. These days’ hybrid sphygmomanometers and finger cuff blood pressure measurement techniques are becoming more popular in the medical setup due to low measurement errors (Ogedegbe & Pickering, 2010). Home blood pressure measurement is another developing method among people because of the convenience to the patient (Boubouchairopoulou & Stergiou, 2016).

    Heart rate is the speed of the heartbeat. It measures by the number of beats per minute (bpm). According to the American Heart Association, heart rate of 60–100 bpm consider as the normal heart rate. Tachycardia is the heart rate above the normal and Bradycardia is considered as the heart rate below the normal range. Lifestyle pattern, physical activity level, genetics, and dietary pattern can alter the blood pressure and heart rate fluctuations. Within those factors, dietary pattern can be recognized as one of the main factors which can change blood pressure and heart rate pattern.

    Based on the systolic and diastolic blood pressure, there are three main categories such as hypertension, hypotension and normal blood pressure. The standard average level of blood pressure is 120/80 mmHg and below the normal is considered as hypotension. Individuals with a systolic blood pressure of 120 to 139 mm Hg or diastolic blood pressure of 80 to 89 mm Hg are considered as prehypertensive and having blood pressure more than 140/90 mmHg considered as hypertensive (Chobanian et al., 2003). In this case those people require health-promoting lifestyle modifications to prevent cardiovascular diseases. Individuals older than 50 years, systolic blood pressure of more than 140 mm Hg is a more important cardiovascular disease risk factor than the diastolic blood pressure. The risk of developing cardiovascular diseases, beginning at 115/75 mm Hg, doubles with each 20/10 mm Hg increment. Individuals who are having normal blood pressure at 55 years of age have a 90% lifetime risk for developing hypertension (Chobanian et al., 2003).

    Obesity, sodium intake, and alcohol consumption influence the blood pressure and the heart rate. Dietary approaches to influence blood pressure and heart rate is becoming more popular than medication because the medication can be lead to various other complications.  Dietary Approaches to Stop Hypertension (DASH) was developed to address hypertension through the diet pattern. Studies have found that the diet rich in fruits, vegetables, and low-fat dairy foods and can substantially lower blood pressure with reduced saturated and total fat. High consumption of fruits and vegetables can include an additional nutritional approach to preventing and treating hypertension (Appel et al., 2002).

Worldwide trends in blood pressure

    A pooled analysis was done in 2017 to estimate worldwide trends in mean systolic and mean diastolic blood pressure from 1975 to 2015 by gathering data from 1479 studies that had measured the blood pressures of 19·1 million adults. The study concluded that, mean systolic and mean diastolic blood pressure decreased substantially from 1975 to 2015 in high-income western and Asia Pacific countries. In central and eastern Europe, also decreased mean blood pressure in women.  In 2015, the highest blood pressure levels were recorded in central and eastern Europe, sub-Saharan Africa, and South Asia. From 1975 to 2015, the number of adults with raised blood pressure increased from 594 million to 1·13 billion and these happened largely in low-income and middle-income countries.  The number of adults with a raised blood pressure around the globe has increased due to population growth and aging, and decreased due to declining age-specific prevalence. (Zhou et al., 2017).

Factors that can affect blood pressure and heart rate

    Factors can be categorized into several factors such as dietary factors, lifestyle factors, physical activity pattern, and genetics. When considering the dietary factors, what we eat can alter the health status of the bay and it may lead to change the normal blood pressure and the heart rate. High sodium intake, high saturated fat consumption, alcohol consumption, and fewer fruits and vegetable consumption can influence the blood pressure. Smoking is one of the primary causative factors which can alter the health condition of the body.  Chemical compounds in cigarettes such as nicotine act as a stimulant and an addictive drug and spike the blood pressure.  Carbon monoxide and some polycyclic aromatic hydrocarbons (PAHs) which are present in tobacco smoke tend to reduce the available oxygenated red blood cells and to compensate the cellular oxygen demand, heart rate and the blood pressure increases.

    Inappropriate lifestyle factors can reduce the quality of life by increasing non communicable disease risk. Elevated blood pressure and heart rate indicate the increased risk of developing non communicable diseases. Being overweight or obese and having less physical activity cause blood pressure fluctuations and these may lead to hypertension like conditions. A clinical trial was conducted in the United States to assess the influence of dietary patterns on blood pressure. They have found that the diet rich in fruits, vegetables, and low-fat dairy products can reduce blood pressure significantly. Researchers have concluded that the diet with a low amount of saturated and total fat also has a positive effect on lowering the blood pressure in hypertensive and normotensive people (Appel et al., 2002). Having a diet with a high amount of fruits, vegetables, and low-fat dairy products provides additional nutritional benefit to prevent and treat hypertension.

    Genetics act as another considerable factor in altering blood pressure and heart rate. Previous studies have found that mutations in at least 10 genes can alter the blood pressure. Findings also confirm that most of these mutations are rare and those can either raise or lower blood pressure. These mutations can alter blood pressure through kidney function such as changing the salt and water reabsorption. (Lifton, 1996).

Coffee

    Coffee is darkly colored, bitter, slightly acidic drink prepared from roasted coffee beans and it has a stimulating effect in humans, primarily due to its caffeine content.  It is one of the most popular drinks in the world and is consumed worldwide in approximately 1.6 billion cups daily. The name "coffee” derived from its botanical name of the plant, Coffea Arabica, which were originated in Ethiopia (Cappelletti et al., 2014).

    The Persian physician Avicenna wrote "The Canon of Medicine” in 1025 by, mentioning coffee as a medication. During that time, coffee was used to clean the skin and gave a better odor to the body. In the 15^th century, Muslims started the diffusion of coffee for providing energy, and remarkably increased coffee houses in Arabia. As sea shipping had expanded in the late 17^th and in the 18^th century, the use of coffee became common in Europe (Cappelletti et al., 2014).

Composition of Coffee

    Every plant-based food products contain phenolic compounds and those are the secondary metabolites involved in plant adaptation to environmental stress conditions. In green coffee beans, Chlorogenic acids (CGA) and related compounds are the main phenolic compounds of reaching levels up to 14 %. These phenolic compounds have many beneficial health properties related to their antioxidant activity as well as hepatoprotective activity, hypoglycemic response, and. caffeoylquinic acids, caffeoylquinic acids, feruloyl quinic acids, and p-coumaroylquinic acids are the main groups of CGA found in green coffee beans and each group contains with at least three isomers. (Farah & Donangelo, 2006).

    Most of the  chlorogenic acid is degraded during the roasting process, therefore, roasted coffee beans contain less antioxidant capacity than green beans (Nebesny et al., 2003, cited in Butt et al., 2011). Robusta coffee beans contain two times higher antioxidant activity level than Arabica coffee, but this difference is no longer significant after the roasting process (Ginz et al., 2000, cited in Butt et al., 2011). Due to the high antioxidant activity, coffee has antibacterial and antiviral properties and these properties are coming from caffeic acid, chlorogenic acid, and protocatechnic acid. (Dogasaki et al., 2002, cited in Butt et al., 2011)

    A study was conducted to evaluate the effect of decaffeination on nutritional and antioxidant status of different coffee brands. Instant coffee, coffee beans, decaffeinated ground coffee, commercial caffeinated ground coffee, and commercial decaffeinated ground coffee brands were used for the study. Caffeine was extracted from the coffee beans to produce decaffeinated coffee. Results showed the highest caffeine percentage on instant coffee while the lowest level of caffeine in commercial decaffeinated ground coffee. Caffeinated ground coffee showed the highest crude fat content as 12.84% and the lowest level of crude fat was found in instant coffee. The highest protein content was found in caffeinated ground coffee and the lowest level was recorded in instant coffee. Decaffeinated coffee and commercial decaffeinated ground coffee showed the highest acidity level and least were found in caffeinated coffee beans. Decaffeinated coffee and the instant coffee showed the highest level of Potassium and decaffeinated coffee showed the highest Zinc level. The highest total phenolic content (TPC) was recorded in caffeinated ground coffee (1720mg/100g) and the lowest level was found in decaffeinated coffee (1490mg/100g). Overall acceptability of these coffee products was analyzed and decaffeinated ground coffee got the best overall acceptability score (Butt et al., 2011)

Worldwide coffee consumption patterns

    According to the International Coffee Organization, International coffee council 112th session, Asia and Europe had the highest coffee consumption rate and the rate was increased drastically from 1990 to 2012.  Central America, North America and South America had the lowest growth rate of coffee consumption.

    It is estimated that 157 million (60kg) bags of coffee were produced globally in 2016 and around 152 million in 2013. The global distribution of coffee production tends to cluster in countries around the equator because of the desirable growing conditions for coffee plants to grow. Brazil has the largest production volumes that naturally make South America the largest producing region and other leading producer countries include Colombia Indonesia and Honduras. Each year, the coffee production naturally fluctuates mainly due to climatic conditions and trading conditions. Papua New Guinea showed the greatest increase in production (64.5%), followed by Uganda (34.3%), Honduras (33%), Peru (27.8%) and Mexico (24.1%) from 2015 to 2016. Yemen experienced the greatest production decline (-33.4%) and Thailand (-29.8%), Cameroon (-27.5%), Togo (-25.9%) and Rwanda (-24.4%) also experienced some production decline. Coffee importing countries had higher level of coffee consumption (107 million bags) compared to the coffee exporting countries (48 million bags) (word press, 2017).

Effects of caffeine consumption

    Based on the reviewed data, it is concluded that for the healthy adult population, caffeine intake of 400 mg per day is not associated with adverse effects such as general toxicity, cardiovascular events, effects on bone health and calcium balance, behavior changes in adults, increased cancer incidents and effects on male fertility. The data also showed that reproductive-aged women and children require specific advice on moderating their caffeine intake. Based on the available evidence, it is suggested that reproductive-aged women should consume 300mg or below 300mg of caffeine per day while children should consume below or equal to 2.5 mg per kg of body weight per day (Nawrot et al., 2003). Caffeine has also been recognized as a compound for weight loss and for the reduction of the overall risks for developing metabolic syndrome (de Mejia & Ramirez-Mares, 2014). Caffeine can be used as a psych stimulant and it is beneficial in restoring low levels of wakefulness and it has the ability to work as a counteracting agent to restore degraded cognitive task performances due to sleep deprivation. Because of that action, caffeine may also affect to the habitual sleep pattern, resulting in daytime sleepiness. These conditions can be observed especially in adolescents (Snel & Lorist, 2011).

    Cholesterol has a positive relationship on the pathogenesis of sporadic Alzheimer's disease, increasing β-amyloid and oxidative stress levels as increased levels of reactive oxygen species and isoprostanes, glutathione depletion, and increased levels of endoplasmic reticulum stress marker proteins. The cholesterol-enriched diet also reduces the levels of adenosine A1 receptors. Caffeine has antioxidant properties and has been demonstrated to reduce β-amyloid levels in mouse models. Caffeine has the ability to reduce the cholesterol-induced increased β-amyloid, phosphorylated tau, and oxidative stress levels and reversed the cholesterol-induced decrease in adenosine A1 receptor levels. These studies have also found that even very low doses of caffeine might protect against sporadic Alzheimer's disease-like conditions (Prasanthi et al., 2010). Some epidemiological reports and experimental models suggested that caffeine has been found to have a positive effect in preventing loss of dopaminergic neurons in Parkinson’s disease (Cappelletti et al., 2014).

    A multi-center, randomized, controlled trial was conducted to see the effect of caffeine on cognitive development, neonatal morbidity, death, and disability with 287 infants with prematurity apnea or in the peri‐extubation period. Cognitive development was measured through the Griffiths Mental Development Scales. Two dosage regimens of caffeine (20 vs. 5 mg/kg/day) were used and the study did not result in adverse outcomes for development, temperament and behavior changes of neonates with the dosage of 20 mg/kg/day (Gray et al., 2011).

Caffeine and blood pressure  

    A review study has shown that in hypertensive patients, caffeine intake of 200 to 300 mg caused an increase in Blood pressure within the first 60 minutes after intake and persisted up to 180 minutes. Hypertensive individuals showed an overall increase of 8 mm Hg in systolic blood pressure and 6mm Hg in diastolic blood pressure. They have also found that drinking coffee for 2 weeks did not increase blood pressure. These studies have also reviewed that habitual coffee consumption does not increase the risk of cardiovascular diseases in hypertensive individuals. The acute effects of caffeine in normotensive individuals reported an elevated blood pressure from 2 to 12 mmHg and 3 to 11 mm Hg for systolic and diastolic blood pressure respectively (Mesas et al., 2011).

    Another antioxidant study suggested that some components in coffee, such as phenolic compounds, magnesium, and trigonelline, improve glucose metabolism and reduce inflammation and endothelial dysfunction. Compounds such as m-coumaric acid and dihydroferulic acid showed high antioxidant activity. The study also proved that these compounds can prevent or reduce the oxidation of low-density lipoprotein (Gómez et al., 2007).

    To see the effect of acute consumption of caffeine on blood pressure, a double-blind crossover study was conducted by recruiting 16 healthy volunteers. The results also showed an unfavorable effect of acute caffeine consumption on wave reflections and therefore on left ventricular (LV) pulsatile afterload (Karatzis et al., 2005).  

    To find the possible combinations of caffeine and exercise on blood pressure (BP) regulation, a placebo-controlled, double-blind crossover study was conducted by recruiting 34 healthy, normotensive  young men of mean age 27 ± 3 years and each subject performed submaximal and symptom-limited maximal supine bicycle exercise 1 hour apart after received the placebo or caffeine. The research concluded that caffeine increases blood pressure additively during submaximal exercise and the effect of caffeine appeared due to the increase of vascular resistance rather than cardiac output (Hodgson et al., 2013).

    Coffee is a plant-based product so it contains many substances which may have an effect of altering the nervous activity, blood pressure, and heart rate other than caffeine. To see the effect of coffee on sympathetic never activity and blood pressure, 6 habitual and 9 non-habitual healthy coffee drinkers were recruited and concluded that there is a significant effect of habitual and non-habitual coffee consumption and also caffeine can alter the sympathetic nervous activity.  Ingredients other than caffeine has an effect on cardiovascular activation because decaffeinated coffee also increased BP and MSA in non-habitual drinkers (Corti et al., 2002).

    Diminished heart rate variability (HRV) is a predictor of chronic heart failure (CHF) due to left ventricular dysfunction. Caffeine showed an increase HRV in young healthy subjects so an increase of HRV maybe has some potential benefit to patients with CHF. To check the effect of caffeine on patients with chronic heart failure, a study was conducted on two separate days with 11 patients and it was concluded that caffeine had no significant effect on any element of HRV among CHF patients (Notarius & Floras, 2012).

Conclusion

    Caffeine intake of 400 mg per day is not associated with adverse effects such as general toxicity, cardiovascular events, effects on bone health and calcium balance etc. Also, some studies suggests that the reproductive-aged women should have specific advises regarding caffeine intake and it was suggested that reproductive-aged women should consume 300mg or below 300mg of caffeine per day while children should consume below or equal to 2.5 mg per kg of body weight per day. Some studies have conducted based on heart failure patients and concluded that caffeine intake of 4g per kg of body weight had no significant effect with heart failures. By reviewing all the data, it can be concluded that caffeine can increase the blood pressure within short period of time after the consumption (60 minutes) and chronic consumption of caffeine also associated with elevated blood pressure, then adaptation to the blood caffeine level and not associated with adverse effects.

    Some components in coffee, such as phenolic compounds, magnesium, and trigonelline, improve glucose metabolism and reduce inflammation and endothelial dysfunction. Compounds such as m-coumaric acid and dihydroferulic acid show high antioxidant activity, which is beneficial to reduce the oxidative stress. Caffeine may also affect to the habitual sleep pattern, resulting in daytime sleepiness.

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