In addition to differences in methods of preparation, conflicting data regarding serving size could partially explain differences between beneficial/harmful effects of coffee consumption.
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Overview of effects of moderate consumption of caffeine, a main active component of coffee
Coffee consumption has been shown to have minimal or no impact, positive or negative, on cancer development; however, researchers involved in an ongoing 22-year study by the Harvard School of Public Health state that "the overall balance of risks and benefits [of coffee consumption] are on the side of benefits." For example, men who drank six or more cups of coffee per day were found to have a 20% reduction in developing prostate cancer. Other studies suggest coffee consumption reduces the risk of being affected by Alzheimer's disease, Parkinson's disease, heart disease, diabetes mellitus type 2, cirrhosis of the liver, and gout. A longitudinal study in 2009 showed that those who consumed a moderate amount of coffee or tea (3–5 cups per day) at midlife were less likely to develop dementia and Alzheimer's disease in late-life compared with those who drank little coffee or avoided it altogether. It increases the risk of acid reflux and associated diseases. Most of coffee's beneficial effects against type 2 diabetes are not due to its caffeine content, as the positive effects of consumption are greater in those who drink decaffeinated coffee. The presence of antioxidants in coffee has been shown to prevent free radicals from causing cell damage. A recent study showed that roast coffee, high in lipophilic antioxidants and chlorogenic acid lactones, protected primary neuronal cell cultures against hydrogen peroxide-induced cell death.
In a healthy liver, caffeine is mostly broken down by the hepatic microsomal enzymatic system. The resulting metabolites are mostly paraxanthines—theobromine and theophylline—and a small amount of unchanged caffeine is excreted by urine. Therefore, the metabolism of caffeine depends on the state of this enzymatic system of the liver. Elderly individuals with a depleted enzymatic system do not tolerate coffee with caffeine. They are recommended to take decaffeinated coffee, and this only if their stomach is healthy, because both decaffeinated coffee and coffee with caffeine cause heartburn. Moderate amounts of coffee (50–100 mg of caffeine or 5–10 g of coffee powder a day) are well tolerated by most elderly people. Excessive amounts of coffee, however, can, in many individuals, cause very unpleasant, exceptionally even life-threatening adverse effects. The benefits of coffee on abnormal liver biochemistry, cirrhosis and hepatocellular carcinoma have been reported, but there is a lack of satisfactory explanation. A possible opposite, if not antagonistic, role of coffee and Mediterranean Diet with regard to overweightness and insulin resistance is envisaged in the natural history of NAFLD (Non-Alcoholic-Fatty-Liver-Disease) . Coffee consumption can lead to iron deficiency anemia in mothers and infants. Coffee also interferes with the absorption of supplemental iron. Interference with iron absorption is due to the polyphenols present in coffee. Four major classes were identified: flavan-3-ols (monomers and procyanidins), hydroxycinnamic acids, flavonols and anthocyanidins. Although the inhibition of iron absorption can cause an iron deficiency, iron is considered a carcinogen in relation to the liver. Polyphenols contained in coffee are therefore associated with decreasing the risk of liver cancer development.
American scientist Yaser Dorri has suggested that the smell of coffee can restore appetite and refresh olfactory receptors. He suggests that people can regain their appetite after cooking by smelling coffee beans, and that this method can also be used for research animals.
Over 1,000 chemicals have been reported in roasted coffee; more than half of those tested (19/28) are rodent carcinogens. Coffee's negative health effects are often blamed on its caffeine content. Instant coffee has a much greater amount of acrylamide than brewed coffee. Research suggests that drinking caffeinated coffee can cause a temporary increase in the stiffening of arterial walls. Caffeinated coffee is not recommended for everybody. It may aggravate preexisting conditions such as gastroesophageal reflux disease, migraines, arrhythmias, and cause sleep disturbances.
Coffee is no longer thought to be a risk factor for coronary heart disease. One study suggests that it may have a mixed effect on short-term memory, by improving it when the information to be recalled is related to the current train of thought but making it more difficult to recall unrelated information. Caffeine has been associated with its ability to act as an antidepressant. A review by de Paulis and Martin indicated a link between a decrease in suicide rates and coffee consumption, and suggested that the action of caffeine in blocking the inhibitory effects of adenosine on dopamine nerves in the brain reduced feelings of depression. A 1992 study concluded that about 10% of people with a moderate daily intake (235 mg per day) experienced increased depression and anxiety when caffeine was withdrawn, but a 2002 review of the literature criticised its methodology and concluded that "the effects of caffeine withdrawal are still controversial." About 15% of the U.S. general population report having stopped drinking coffee altogether, citing concern about health and unpleasant side effects of caffeine.
Coffee is not completely innocent. Caffeine, coffee's main ingredient is a mild addictive stimulant. And coffee does have modest cardiovascular effects such as increased heart rate, increased blood pressure, and occasional irregular heartbeat that should be considered. Studies have been largely inconclusive regarding coffee and its effect on women's health issues such as breast health, cancer, and osteoporosis. But, the negative effects of coffee tend to emerge in excessive drinking so it is best to avoid heavy consumption.
Coffee is not completely innocent. Caffeine, coffee's main ingredient is a mild addictive stimulant. And coffee does have modest cardiovascular effects such as increased heart rate, increased blood pressure, and occasional irregular heartbeat that should be considered. Studies have been largely inconclusive regarding coffee and its effect on women's health issues such as breast health, cancer, and osteoporosis. But, the negative effects of coffee tend to emerge in excessive drinking so it is best to avoid heavy consumption.
Caffeine and headaches
There is some controversy over whether the caffeine in coffee causes headaches or helps relieve headaches. In a 2000 controlled study by the Diamond Headache Clinic in Chicago, Illinois, revealed that adults who took ibuprofen, an over the counter pain killer, combined with caffeine or one cup of coffee had increased effectiveness against tension headaches. The study did not recommend that the caffeine and ibuprofen combination was effective against migraine headaches. A Johns Hopkins controlled study has linked drinking coffee with addictive withdrawal headaches, even with those who drink coffee in moderation. A 2009 Norwegian University of Science and Technology controlled study claims that heavy coffee drinkers, four cups a day, are more likely to suffer occasional headaches than persons who have low coffee or caffeine consumption.
Caffeine molecule
Caffeine content
The stimulant effect of coffee is due to its caffeine content. The caffeine content of a cup of coffee varies depending mainly on the brewing method, and also on the variety of bean.
According to Bunker and McWilliams (J. Am. Diet. 74:28–32, 1979), coffee has the following caffeine content:
brewed: 1 cup (7 oz, 207 ml) = 80–135 mg.
drip: 1 cup (7 oz, 207 ml) = 115–175 mg.
espresso: 1 shot (1.5–2 oz, 45–60 ml) = 100 mg
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