The consumption of coffee, both caffeinated and decaffeinated, has positive and negative impacts on health. Caffeine affects the central nervous system, along with the digestive, excretory, circulatory, respiratory, skeletal, muscular, and reproductive systems—but these effects are not necessarily negative.

Caffeine stimulates our brain. It makes us feel alert and less tired. Caffeine can be used instead of over-the-counter drugs to treat headaches, drowsiness, and migraines. According to a 2009 University of Florida study, a habit of caffeinated coffee in our 40s and 50s may reduce our risk of getting Alzheimer’s disease or dementia by 70 per cent. Other studies suggest that regular consumption may help reduce the rate of cognitive decline in older adults.

According to a 2013 Harvard School of Public Health study, intake of two-to-three cups of caffeinated coffee daily caused a 45 per cent reduction in suicide rate. The reason may be that caffeine’s stimulant effect that boosts our moods. Caffeine also reduces risk of oral cancer. Decaf has a lower effect in reducing risks of oral cancer.

Unfortunately, people can develop an addiction to caffeine. Sudden stops or breaks can cause withdrawal effects such as headaches, anxiety, irritability, and drowsiness. Some may even experience tremors—the sudden involuntary body movements, mainly in the hands. Some can even overdose on caffeine. The symptoms of an overdose are confusion, vomiting, and hallucinations. Overdose can cause irregular or rapid heartbeat, along with difficulty in breathing and can also lead to death due to convulsions.

Caffeine increases the amount of acid in our stomachs, which can cause heart burn or an upset stomach. Since extra caffeine cannot be stored in our bodies, we might experience increase in urination. People with acid reflux or ulcers are advised to consult their doctors before consuming caffeine.

Caffeine in large amounts may interfere with absorption and metabolism of calcium. A lack of calcium may lead to weakening of bones, or more seriously, osteoporosis. Caffeine may also cause muscles to twitch or ache. For pregnant women, caffeine can be hazardous—it enters the bloodstream and gains access to the placenta and goes into the baby’s bloodstream. This causes a baby’s heartbeat and metabolism to increase. Too much caffeine can cause miscarriages or slow fetal growth.

Decaffeinated coffee is rarely studied or considered. Decaf has 97 per cent of the caffeine removed and it contains antioxidants and nutrients. Antioxidants are contained in both regular and decaf coffee. The main antioxidants are hydrocinnamic acid and polyphenols. This prevents heart diseases, cancer, and type 2 diabetes. A cup of coffee daily may reduce risk of type 2 diabetes by seven per cent. Decaf also contains small amounts of required nutrition, such as magnesium, potassium, niacin, and vitamin B3.

Decaf may also be involved in reducing the risk of premature birth. According to two human cell studies, decaf may protect neurons in the brain which can help prevent Alzheimer’s disease and Parkinson’s disease. These benefits are shared with regular coffee.