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There is a good deal of debate about the health effects of caffeine, and whether these effects are primarily positive or negative.

Caffeine, particularly in coffee, has been studied closely to determine where it may be of benefit, and where it may cause undesirable effects.

Health benefits of caffeine

Parkinson's disease

Parkinson's is caused by the loss of brain cells that produce a chemical messenger called dopamine. According to a researcher from the Harvard School of Public Health in Boston, people who drink coffee or consume caffeine regularly have a lower risk of developing Parkinson's disease. The research put forth that the mice that had first been given caffeine equivalent to moderate amounts of coffee in humans lost fewer neurons than those not given caffeine.

Caffeine also seems to protect human brain cells. In a meta-analysis that pooled 13 studies, drinkers of regular coffee - but not decaf - had a 30 percent lower risk of Parkinson's disease than non-drinkers. There are at least six studies indicating that people who drink coffee on a regular basis are up to 80% less likely to develop Parkinson's, with three showing the more they drink, the lower the risk.

The theory is that caffeine reduces the amount of neurotransmitters produced by the brain, transmitters that may cause damage to surrounding brain tissue. The actual action of caffeine in the brain is not known. It may also interfere with uptake of other transmitters, allowing the levels of dopamine to increase.


The Nurses' Health Study and the Health Professionals Follow-up Study put forth that those who drank two to three cups of regular coffee a day had about a 20 percent lower risk of gallstones than non-drinkers. Another research showed that compared to not drinking coffee, at least two cups daily can result in a 25% reduced risk of colon cancer, an 80% drop in liver cirrhosis risk, and nearly half the risk of gallstones. Here, it is important to remember that tea, decaf coffee, and caffeinated soft drinks aren't protective.

Caffeine has several metabolic effects that reduce the risk of gallstones. One probable explanation is that caffeine may stimulate the gallbladder to contract, which helps empty it of stone-forming cholesterol and bile pigments.

Mental performance

Caffeine improves alertness and reaction time in people, whether they are habitual consumers of caffeine or not. The caffeine in a cup of coffee stimulates the central system as it simultaneously lowers the blood sugar and increases the brain's demand for sugar. The result is a temporary lift. But the effect of caffeine is clearly limited to the ability to maintain attention and it doesn’t improve memory or complex reasoning.

The impact appears to be greater in sleep-deprived individuals. French researchers accompanied young males as they drove 125 miles on a highway in the early morning hours. When the young men were given coffee with 200 mg of caffeine before getting behind the heel, they unconsciously crossed into another lane an average of two times during their drive. When they were given decaf, they crossed an average of six times.


The mood altering effects of caffeine depend on the amount of caffeine consumed and whether the individual is physically dependent on or tolerant to caffeine. In caffeine non-users or intermittent users, low doses of caffeine (20-200 mg) generally produce positive mood effects such as increased well-being, happiness, energetic arousal, alertness, and sociability.
Among daily caffeine users, much of the positive mood effect experienced with consumption of caffeine in the morning after overnight abstinence is due to suppression of low grade withdrawal symptoms such as sleepiness and lethargy. Large caffeine doses (200 mg or greater) may produce negative mood effects. Although generally mild and brief, these effects include increased anxiety, nervousness, jitteriness, and upset stomach.

Physical performance

There is evidence that caffeine can improve physical performance.  In a study on recreational athletes, the consumption of about five cups of coffee significantly increased muscle endurance during brief, intense exercise.  Prior to a maximum effort run, caffeine consumption of about three cups of coffee resulted in significantly greater anaerobic metabolism and improved athletic performance among recreational runners.

Caffeine helps the body burn fat instead of carbohydrate, and it blunts the perception of pain. Both can boost endurance. Aerobic physical endurance is improved in people who run, job, swim or cycle and they last longer on consumption of 200 mg to 600 mg of caffeine beforehand. A new research suggests that caffeine can also improve anaerobic performances, which include lifting heavy objects and sprinting short distances.


During a headache, the blood vessels in brain dilate, or become wider. Caffeine causes blood vessels to constrict, thus it can help relieve headache pain. It is also a mild analgesic. Caffeine makes pain relievers 40% more effective in relieving headaches and helps the body absorb headache medications more quickly, bringing faster relief. For this reason, many over-the-counter headache drugs include caffeine in their formula. It is also used with ergotamine in the treatment of migraine and cluster headaches as well as to overcome the drowsiness caused by antihistamines.

Heart health

Results of a study published in The Journal of Clinical Nutrition put forth that moderate coffee intake can help prevent some cardiovascular problems. Coffee is full of antioxidants which are good for both the heart and the body. Coffee can also reduce inflammation and this too helps prevent certain heart related illnesses.

Another study published in the Annals of International Medicine found that women who drink two to three cups of coffee a day have a 25% lower risk of heart disease and an 18% lower risk of developing diseases other than cancer than non-coffee drinkers.

Negative health effects of caffeine


There is a significant association between drinking caffeinated coffee and decreasing bone mineral density at both the hip and the spine that comes with aging and leads to osteoporosis, a major cause of fractures in the elderly. There occurs a loss of up to 5 milligrams of calcium for every six ounces of regular coffee or two cans of cola. As little as 300 to 400 mg of caffeine a day doubles the risk of hip fracture.


Daily consumption of caffeine in coffee, tea or soft drinks increases blood sugar levels for people with type 2 diabetes and may undermine efforts to control their disease. Researchers at Duke University Medical Center found that consumption of caffeine raised the average daily sugar levels by 8 per cent. Caffeine also exaggerated the rise in glucose after meals: increasing by 9 percent after breakfast, 15 percent after lunch and 26 per cent after dinner. This study suggested that one way to lower blood sugar is to simply quit drinking coffee, or any other caffeinated beverages.

A study published in the journal Diabetes Care indicated that diabetics who consume roughly four cups of caffeine may experience a significant increase in blood sugar. Previous studies have shown that caffeine could increase the body's insulin resistance, leading to an increase in blood sugar levels.

Loss of sleep

Caffeine taken during the day may prevent from falling asleep at night, shortening the normal length of time of sleep. Caffeine is said to block the effects of adenosine, a neurotransmitter thought to promote sleep. Caffeine also increases the number of times you wake up during the night by increasing the need to urinate and interfering with deep sleep. This leads to poor quality of sleep and fatigue during the day, which in turn triggers you to take more caffeinated drinks in a negative feedback cycle. The same caffeinated beverage that helps people mask their sleepiness also makes them irritable, stressful, fatigue, hostile, and less productive. 

Fertility and miscarriage

Earlier studies found that it takes at least 300 milligrams of caffeine in a day to affect fertility. Low to moderate caffeine consumption doesn't seem to reduce a woman's chance of becoming pregnant.

Various other studies have shown that women who drink one to one and a half cups of coffee each day had up to a 50% reduction in fertility. Three cups a day has been linked to early miscarriage (new evidence shows 200 milligrams as the limit). Though there are some women who conceive while drinking multiple cups of coffee a day and drink it during their entire pregnancy yet one should remember that each of our bodies are so very different and what effects one women will have no effect on the other.

The good and bad of caffeine

Caffeine is part of modern life. Regular coffee drinkers include the majority of U.S. adults and a growing number of children. The recommendation for most people is to enjoy one or two cups of coffee a day, which will allow you to capitalize on its health benefits without incurring health drawbacks. Extensive recent research has put forth that coffee is far more healthful than it is harmful. Very little bad and a lot of good come from drinking it.