Normally, up to 400 milligrams of caffeine in a day is considered safe for most adults. This comes to around four cups of coffee.

A number of people drink coffee several times a day for the reason that it makes them stay alert and focused. Coffee has its good and bad side as experts explain:

Moderate coffee consumption (three to four cups per day) has been linked with longer lifespan. A November 2015 study in Circulation found that coffee consumption was associated with an eight per cent to 15 per cent reduction in the risk of death (with larger reductions among those with higher coffee consumption). 

Other studies have found that coffee drinkers may have a reduced risk of cardiovascular disease (including heart attack, heart failure, and stroke), type 2 diabetes, Alzheimer’s disease and Parkinson’s disease, colon, uterine and liver cancer and cirrhosis. 

Dieudonne Bukaba, a nutrition expert based in Kigali, notes that coffee prevents many cancers. For example, coffee consumption has been linked with reduction of cancers of the oral cavity and skin. 

Studies show coffee may play a role in the prevention of cancers of the breast and colon and may also help to reduce the risk of recurrence in survivors of both. 

New study shows that coffee may even provide benefits once cancer has spread. A 2020 study published in the journal JAMA Oncology found that when individuals with metastatic colon cancer consumed about two to three cups of coffee a day, they increased the time it took for the disease to worsen and the chances of living longer.

Bukaba adds that people who consume coffee may have a lower risk of gallstone disease. Gallstones are hardened deposits of digestive fluid that can form in the gallbladder.

There’s evidence, published in a July 2015 review in Alimentary Pharmacology and Therapeutics, that drinking coffee triggers the release of cholecystokinin, a substance that promotes gallbladder contraction and stimulates the release of bile.

Researchers from another observational study published in the Journal of Internal Medicine in September 2019, observed that those who drank at least six cups of coffee per day had as much as a 23 per cent lower risk of symptomatic gallstone disease.

Bukaba says that coffee boosts one’s physical performance as it activates areas of the brain and nervous system to improve focus and energy, while lowering tiredness. 

The dark side 

Although coffee is known to prevent some cancers, it may raise risks to other cancers. In a 2016 report, the World Health Organization (WHO) raised concerns that drinking coffee (or other beverages) at temperatures higher than 149 degrees Fahrenheit may increase the risk of oesophageal cancer. 

Since coffee contains caffeine, WHO states that coffee is one of the most common sources of high caffeine intake. During pregnancy, caffeine clearance from the mother’s blood slows down significantly. Results from some observational studies suggest that excess intake of caffeine may be associated with growth restriction, reduced birth weight, preterm birth or stillbirth.

WHO recommends pregnant women with high daily caffeine intake (more than 300 mg per day), to lower daily caffeine intake during pregnancy as it is suggested to reduce the risk of pregnancy loss and low birth weight neonates.

Bukaba states that an increased intake of coffee can dehydrate one’s body, dries and dulls the skin, and causes fatigue.

Coffee is also known to cause heartburn as it is naturally acidic. When your caffeine intake is too high, the muscle that connects the stomach to the oesophagus is relaxed. When this happens, an opening is created for stomach acid to come up into your oesophagus, which causes acid reflux, he adds. 

Medicine Net states that excess coffee intake is known to increase bone loss in postmenopausal women (if diets lack enough intake of calcium), increased cholesterol levels (due to unfiltered, unboiled coffee), nervousness, restlessness, increased anxiety levels, muscle tremors, insomnia (trouble falling asleep or staying asleep), pounding heart or missed beats, abnormal heart rhythm and continuous urinating.