Caffeine: Friend or Foe?
Caffeine is a mild stimulant which promotes metabolism of carbohydrates. About 80% of the worlds’ adults consume caffeine daily. Caffeine is found in over 60 plants worldwide. A cup of coffee contains about 135 milligrams of caffeine, a cup of tea about 40 milligrams, 12 ounces of cola contains about 50 milligrams, energy drinks contain up to 150 milligrams per serving, and 1 ounce of chocolate contains about 30 milligrams. Caffeine is also added to some forms of aspirin like Excedrin and to stay-awake medicines like Vivarin. The average caffeine consumption among US adults is about 300 milligrams per day.
Caffeinated beverages have been used for thousands of years to help people stay awake and alert. A number of studies have confirmed that caffeine increases alertness, reduces fatigue and increases performance on complex tasks. On the other hand, heavy caffeine consumption has been shown to increase risk of insomnia and anxiety- especially in sensitive individuals. Caffeine consumption should be avoided late in the date in people with a tendency to insomnia.
Some people consume caffeinated beverages to counteract the effects of lack of sleep. However, many studies have shown that inadequate sleep greatly increases the risk of road and industrial accidents- even among those consuming caffeine. The use of the caffeinated beverages should not be used as a sleep substitute.
Caffeine may have mildly addictive effects. Heavy coffee drinkers often report fatigue, depression and headaches if they abruptly discontinue their coffee consumption.
Some studies have found that even modest caffeine consumption in children can increase risk of insomnia and ADHD= attention deficit hyperactivity disorder. Concern has also been raised that consuming large amount of soft drinks can reduce consumption of milk in children and cause risk for lack of calcium.
Some studies have suggested that heavy consumption of caffeine can increase risk of bone loss- while other studies report no such association. To avoid bone problems later in life- it is critical that children and adults eat a diet rich in calcium, magnesium, phosphorus and vitamin D. Getting weight bearing exercise such as walking, jogging and weight lifting is also critical for maintaining healthy bones. Among people who already have weak bones (osteoporosis) a number of studies have found that consumption of strontium supplements are helpful for reversing bone loss and reducing risk of bone fracture.
Caffeine is a mild heart stimulant. Some studies of human populations have reported that caffeine consumption can increase blood pressure and rates of heart irregularities (arrhythmias), while other studies have found that caffeine is not related to blood pressure or arrhythmias. People react differently to caffeine and a few individuals may be very sensitive to the blood pressure raising and arrhythmic effects of caffeine.
Caffeine may be mildly helpful for asthmatics. Caffeine was prescribed in ancient Greece to treat asthma. However, inhaled and oral asthma medications are generally much more effective for controlling asthma than is caffeine. For maximum asthma control- asthmatics should avoid common airborne asthma triggers like air pollution, second hand tobacco smoke, pesticides and poor ventilation. Consumption of a well balanced diet rich in fruits and vegetables, calcium, magnesium, anti-oxidant vitamins A, C, E, and fish or fish oil can also be helpful for many asthmatics.
It is not certain how much caffeine is safe to use during pregnancy. Some recent studies have linked heavy caffeine consumption to significantly increased risk of miscarriage (Am J Obstet Gynecol 2008;198(3):e1-e8)and neural tube defects (such as spina bifida) (Birth Defects Research and Clinical Molecular Teratology, in press 2009). Other studies have found no relationship between caffeine consumption and birth defects and miscarriages. The American College of Obstetrics and Gynecology recommends no more than the caffeine equivalent of 2 cups per day during pregnancy. It is important that pregnant women receive a good diet and a well balanced food supplement containing iron, folate (folic acid) and vitamin B12. Several studies have reported that taking a supplement with folate during pregnancy can significantly reduce rates of birth defects such a spina bifida.
Coffee and tea are sometimes infested with molds which can produce mycotoxins. Be sure to use only fresh coffee or tea and throw out any product which becomes moldy or rancid.
Caffeine has both positive and negative health effects. Much more research on the effects of caffeine- positive and negative is needed. Adults should consume caffeine in moderation and eat a well balanced diet. Caffeinated drinks should be limited in children and should not replace other more nutritious drinks like milk and water.
A good review of the effects of caffeine and health can be found in Food and Chemical Toxicology 2002;40:1243-55.