General health 

Dr MS Purkait – medical superintendent, Techno India DAMA Hospital

Black coffee has been proven to have several positive effects on the human body. In moderate amounts, it acts as a stimulant, helping the brain function faster and better because it boosts the production of neurotransmitters like dopamine and serotonin. It also helps in increasing the metabolism, which might help in weight reduction. It also acts as a diuretic, helping the kidney and liver rid of toxins. Local application on skin can give protection from harmful UV rays. Drinking 2 cups of black coffee a day after food might be helpful, but in excessive amounts and on an empty stomach negates all these positive effects.

However, consuming excessive amounts on an empty stomach can cause irritation, giving rise to feelings of bloating, cramps and acid reflux. It can cause a transient rise in blood pressure and an increased heart rate. Sometimes it can cause increased anxiety or nervousness in some people. Often, it can cause headaches and nausea.

In addition, excessive coffee intake can cause insomnia and disturb the sleep pattern in some people.

Eye care 

Dr Anindya Kishore Majumder, Uveitis specialist, Asian Institute of Immunology and Rheumatology                 

Many studies showed there is an acute rise in intraocular pressure both in glaucoma patients and in normal individuals with consumption of large amounts of caffeine. So it was a common belief that consumption of caffeine could increase the intraocular pressure. Actually, the consumption of a large amount of caffeine increases the risk of glaucoma more than three times for those with a genetic disposition of higher intraocular pressure. In a multicentric study, US-based studies showed a higher caffeine intake increases the risk of glaucoma in genetically susceptible individuals who have a family history of glaucoma.

A higher amount of daily caffeine intake—more than 480 milligrammes, approximately 4 cups of coffee—increases the intraocular pressure. .35 mm of mercury in a normal individual compared to the genetically predisposed individual who showed a threefold rise in intraocular pressure with 321 milligrammes of daily caffeine that is more than equal to 3 cups of coffee. So a normal caffeine intake has a minimal or insignificant rise of intraocular pressure.