While clinical responses of Caffeine are widely understood the cellular basis is not well known. (Coffee House)"Currently, it is believed that xanthines act as adenosine-receptor antagonists. Adenosine acts as an autocoid, and virtually every cell contains adenosine receptors within the plasma membrane. Adenosine exerts complex actions. It inhibits the release of neurotransmitters from presynaptic sites but works in concert with norepinephrine or angiotensin to augment their actions. Antagonism of adenosine receptors by caffeine would appear to promote neurotransmitter release."(Coffee House) In other words, the molecular structure of the caffeine molecule is similar to that of adenosine. *
This similarity results in the caffeine molecule binding to the nerve cell membrane. Therefore, the signal to stop producing adenosine that would have been sent by the adenosine becomes blocked, which results in a surplus of adenosine and explains the stimulatory effects of caffeine.
Decades of research and centuries of human consumption suggest the relative safety of caffeine. According to the National Library of Medicine, more than 19, 000 scientific studies to date have been conducted on caffeine, and the US Food and Drug Administration still considers caffeine to be "Generally Recognized as Safe." A study at the University of California showed that the average daily consumption of 200 mg as safe.(Ascherio) The study also concluded that the the lethal dose of caffeine is 192 mg/kg, meaning for the average american would need to drink more than 150 cups of coffee to reach lethal overdose!(Bobrow) Caffeine enhances performance on observational and simple tasks that require sustained response. These effects are in tired or bored subjects, although there is evidence that benefits may still occur when the person is unimpaired. (Smith) Caffeine also boosts the numbing effect of aspirin, and recent scientific research carried out at the Mayo clinic, Harvard School of Public Health, US Veterans Administration and other medical centers show that caffeine is not only safe but also beneficial. The study showed that drinking from 2-4 cups of coffee a day may lower the risk of colon cancer (40%), gallstones (45%), cirrhosis of the liver (80%), and Parkinson's disease (50-80%), among other diseases. (Ascherio) A study at University of Creighton published in 2002 states that there is no evidence that caffeine has any harmful effect on bones in individuals who ingest the currently recommended daily allowances of calcium. (Heaney) A similar group of large-scale studies at Cardiff University showed no evidence of negative effects of caffeine withdrawal on mood and performance. In addition, the American Medical Association recently stated that there is no relationship between caffeine intake and any kind of cancer. (Smith) This essay from coursework.info
According to Stephen Cherniske, M.S. (Research and Clinical Nutritionist) Caffeine causes cardiovascular disease, raises blood pressure, raises cholesterol levels,
raises homocysteine levels (high homocysteine levels damage artery walls) and is a greater contributor to heart disease than cholesterol. Caffeine was also found to cause anxiety, irritability, anger, panic attacks, depression, changes brain chemistry, decreased overall mental acuity, fatigue, insomnia, and headache. (Cherniske) Professor Jack James of the University of Ireland conducted studies that showed that long-term caffeine consumption contributes to adrenal insufficiency, and adversely affecting over 150 hormones . Meaning stress , blood pressure, blood sugar, mineral levels, immune activity, inflammation, cell growth and repair are all negatively affected. Other studies showed caffeine contributed to problems like: Gastritis, acid reflux, ulcers, irritable bowel syndrome, hypoglycemia, vitamin loss, PMS, fibrocystic breasts, premenopausal symptoms, decreased fertility, birth defects, asthma, fibromyalgia, chronic fatigue, autoimmune disease and rheumatoid arthritis.(James)
Many studies have suggested a relationship between chronic caffeine use and a number of diseases. However, the cause-and-effect evidence is difficult to prove because of lifestyle variables among the subjects in the studies (eg. smoking, alcohol consumption, exercise), differences in genetic inheritance, form of caffeine intake (coffee, tea, sodas), and the presence of other biologically active substances in the beverage. (Brice) The consumption of caffeine does have side effects, some negative and some positive, but it is clear that when taken in moderation caffeine is never adverse to ones health. However, caffeine consumers should be aware of withdrawal and keep themselves up to date on the latest caffeine research.
