Coffee is a non-alcoholic beverage that is widely consumed by the public. Nevertheless, coffee reaps the controversy, whether it is beneficial or harmful to health. Around the world, coffee is the second-largest trading commodity after oil. The most active components found in coffee are caffeine, chlorogenic acid, cafestol, and kahweol.

Caffeine is a methyl-xanthine derivative that is used as a stimulant and bronchodilator. The caffeine content in coffee depends on how processed (boiled, filtered, or espresso). In America, the standard level of caffeine in roasted coffee is around 85 mg, instant coffee is around 60 mg, decaffeinated coffee is around 3 mg, and one serving of espresso is around 200 - 300 mg.

In the blood, caffeine acts as an antagonist of adenosine receptors found in various tissues such as the central nervous system, endothelium, heart, liver, fat, and muscle tissue. Caffeine affects the cardiovascular system and the central nervous system, modifies carbohydrate metabolism, influences the inflammatory process, increases metabolic rate and diuresis.

The second coffee component is chlorogenic acid, a form of polyphenols found in cocoa and coffee, which has anti-oxidant potential. In one serving, coffee contains 20 - 675 mg of chlorogenic acid, depending on the method and amount used during the process. The next components are cafestol and kahweol, which are components in coffee filtered in a paper filter.

Effects of Consuming Coffee for Health, are Good or Bad?

So is coffee good or bad for health?

Study Limitations regarding coffee

As explained earlier, the active component in coffee varies, depending on the method and amount used during the process. Nevertheless, a study regarding coffee generally did not include making coffee drinks, but only the amount of coffee consumed (cups per day). It certainly causes a bias so that it appears difficult to compare one research to another.

Coffee Effects on the Cardiovascular System

The effects of coffee on the cardiovascular system are still under debate. Caffeine is one of the coffee components that play a role. Caffeine has the following effects related to the cardiovascular system:

a.Endothelium (immediate effect)
- Activation of the ryanodine canal in the endoplasmic reticulum
b. Smooth muscle cells in blood vessels (immediate effect)
- Inhibits IP3 receptors
- Inhibits MLC kinase
- Increases non-contractile Ca2 +
- Inhibits voltage-dependent calcium channels
- blocks adenosine receptors
c. Smooth muscle cells in blood vessels (indirect effect)
- Increases nitric oxide production
- Increases renin production
- Stimulates the sympathetic system

In a meta-analysis study involving 35 cohort studies and more than 1 million samples, there was a non-linear association between coffee consumption and cardiovascular events [6]. In another meta-analysis study, coffee consumption (1-4 glasses per day) significantly reduced the risk of coronary heart disease (RR 0.82, 95% CI 0.73-0.92, p <0.001 in women and RR 0.87, 95% CI 0.80 - 0.86, p = 0.001). While for more consumption (more than 4-5 glasses per day), there is a risk of coronary heart disease that is not significantly different from the consumption of light coffee (less than 1-2 cups per day), p value> 0.05.

There is an overlapping range because different definitions of light, medium, and heavy coffee consumption are included in the studies included [7]. However, several other studies found that coffee consumption affects the increased risk of myocardial infarction [8]. So, it still needs further research to conclude the effect of coffee on heart disease.

One cup of coffee can increase systolic pressure by 2.04 mmHg (95% CI, 1.10 - 2.99) and diastolic 0.73 mmHg (95% CI, 0.14 - 1.31) [9]. Consuming 1-3 cups of coffee per day increases hypertension risk, but consuming more than 3 cups per day does not increase the risk. It is likely because consuming higher coffee increases tolerance to caffeine's acute hemodynamic effects [10].

A meta-analysis involving five prospective studies showed a J-shaped relationship between coffee and heart failure. The highest risk of heart failure is reduced by consuming 4 glasses per day (11% reduction) and consuming less than 4 glasses per day and more from 10 glasses per day back to baseline. There was no association with gender, cardiac history, and diabetes [11].

Caffeine is not associated with an increased risk of atrial fibrillation (OR 0.92, 95% CI, 0.82 - 1.04). Low-dose caffeine (no dose is mentioned) may have a protective effect because the odds ratio drops by 13% (OR 0.85, 95% CI, 0.78 - 0.92) [12]. There is no association between long-term caffeine consumption and Premature Atrial Contraction (PAC) or Premature Ventricular Contraction (PVC) [13].

Coffee Effects on the Cerebrovascular System

Long-term coffee consumption is not associated with an increased risk of stroke in women. Routine decaffeinated coffee consumption is associated with a reduced stroke (RR 0.89; 95% CI, 0.73 - 1.08). Consuming up to 4 drinks per day reduces stroke risk by 17% (RR 0.83, 95% CI, 0.77 - 0.97) compared to non-coffee consumption. This ratio rate is not much different between hemorrhagic and ischemic stroke. Chlorogenic acid has a blood pressure reduction effect and a possible reduction in lipid peroxidation [14-16].

Coffee Effects on Diabetes mellitus

  • A meta-analysis involving 6 studies found that consuming 3-4 cups of decaffeinated coffee per day can reduce the risk of developing diabetes mellitus by 46% (RR 0.64, 95% CI, 0.54-0.77). Consumption of coffee, both regular and decaffeinated coffee, preferably after lunch, might affect glucose metabolism.

Coffee Effects on Cancer

Coffee consumption is not associated with cancer risk in general. In several studies stating that coffee reduces the risk of some cancers [18-21]:

  • Consuming 1 cup of coffee per day reduces the risk of liver cancer by 15%.
  • Consuming 1 cup of coffee per day reduces the risk of endometrial cancer by 8%.
  • Possible to reduce oropharyngeal cancer risks.
  • Consuming coffee more or equal to 4 glasses per day, especially in postmenopausal women, reduce breast cancer by 8%.
  • Consuming coffee more than or equal to 6 glasses per day reduces prostate cancer risk, possibly due to the effects of components other than caffeine.
  • consuming more than 3 glasses per day decreases the risk of basal cell carcinoma
  • Possible reduction in risk for malignant melanoma
  • Consuming more than 2.5 glasses per day reduces the risk of colorectal cancer.

Coffee Effects  on the Central Nervous System and Mental Health

  • In addition to the effect of rapidly increasing concentration, the long-term impact of consuming 3 to 5 cups of coffee per day can reduce the risk of worsening MCI (mild cognitive impairment).
  • It is possible that coffee can reduce the risk of dementia / Alzheimer's and Parkinson's disease [23].
  • Coffee can reduce the risk of depression. On consuming more than 4 drinks per day, the risk of depression decreases by 20% (RR 0.8, 95% CI 0.64 - 0.99) [24].

Coffee Effects on Hepatitis

  • The amount of caffeine consumed was found to be related to the severity of non-alcoholic liver disease (p <0.05) [25]
  • Caffeine has also been found to reduce the risk of cirrhosis in several case-control studies [8]
  • In people with a genetic predisposition to alcoholic hepatitis, those who do not consume coffee regularly have a higher risk of developing hepatitis [26].

Coffee Effects  on the eyes

  • Coffee containing at least 182 mg of caffeine can statistically increase intraocular pressure and ocular perfusion, but this is not clinically meaningful [27].

Coffee Effects on Mineral Absorption

  • Coffee consumption of 150-250 mL can reduce iron absorption by 24-73% and is reversible by stopping coffee consumption.
  • Bioavailability of zinc in vitro is inhibited by coffee by 21 - 32%; this is presumably due to the zinc chelation compounds found in coffee [8].

Source: Alomedika
Writer: Dr. Nathania

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