Coffee and health

Coffee contains several compounds which are known to affect human body chemistry. The coffee bean itself contains chemicals which are psychotropic (in a way some find pleasing) for humans as a by-product of their defense mechanism. These chemicals are toxic in large doses, or even in their normal amount when consumed by many creatures which may otherwise have threatened the beans in the wild.

Coffee as a stimulant
Coffee contains caffeine, which acts as a stimulant. For this reason, it is often consumed in the morning and during working hours. Students preparing for examinations with late-night "cram sessions" frequently use coffee to keep themselves awake. Many office workers take a "coffee break" when their energy is diminished.

Recent research has uncovered additional stimulating effects of coffee which are not related to its caffeine content. Coffee contains an as yet unknown chemical agent which stimulates the production of cortisone and adrenaline, two stimulating hormones.

For occasions when one wants to enjoy the flavor of coffee with almost no stimulation, decaffeinated coffee (also called decaf) is available. This is coffee from which most of the caffeine has been removed, by the Swiss water process (which involves the soaking of raw beans to absorb the caffeine) or the use of a chemical solvent such as trichloroethylene ("tri"), or the more popular methylene chloride, in a similar process. Another solvent used is ethyl acetate; the resultant decaffeinated coffee is marketed as "natural decaf" because ethyl acetate is naturally present in fruit. Extraction with supercritical carbon dioxide has also been employed.

Decaffeinated coffee usually loses some flavor over normal coffees and tends to be more bitter. There are also coffee alternatives that resemble coffee in taste but contain no caffeine (see below). These are available both in ground form for brewing and in instant form.

Caffeine dependency and withdrawal symptoms are well-documented; see Caffeine for more on the pharmacological effects of caffeine.

Reduced risk of Alzheimer's disease
Several studies comparing moderate coffee drinkers (about 2 cups a day) with light coffee drinkers (less than one cup a day) found that those who drank more coffee were significantly less likely to develop Alzheimer's disease later in life.

Reduced risk of gallstone disease
Drinking caffeinated coffee has been correlated with a lower incidence of gallstones and gallbladder disease in both men and women in two studies performed by the Harvard School of Public Health. A lessened risk was not seen in those who drank decaffeinated coffee.

Reduced risk of Parkinson's disease
A study comparing heavy coffee drinkers (3.5 cups a day) with non-drinkers found that the coffee drinkers were significantly less likely to contract Parkinson's Disease later in life. . Likewise, a second study found an inverse relationship between the amount of coffee regularly drunk and the likelihood of developing Parkinson's Disease.

Cognitive performance
Many people drink coffee for its ability to increase short term recall and increase IQ.

Likewise, in tests of simple reaction time, choice reaction time, incidental verbal memory, and visuospatial reasoning, participants who regularly drank coffee were found to perform better on all tests, with a positive relationship between test scores and the amount of coffee regularly drunk. Elderly participants were found to have the largest effect associated with regular coffee drinking. Another study found that women over the age of 80 performed significantly better on cognitive tests if they had regularly drunk coffee over their lifetimes.

Analgesic enhancement
Coffee contains caffeine, which increases the effectiveness of pain killers, especially migraine and headache medications. For this reason, many over-the-counter headache drugs include caffeine in their formula.

Antidiabetic
Coffee intake may reduce one's risk of diabetes mellitus type 2 by up to half. While this was originally noticed in patients who consumed high amounts (7 cups a day), the relationship was later shown to be linear.

Anticancer
Coffee can also reduce the incidence of cirrhosis of the liver and has been linked to a reduced risk of hepatocellular carcinoma, a primary liver cancer. Coffee consumption is also correlated to a reduced risk of oral, esophageal, and pharyngeal cancer.

Cardioprotective
Coffee reduces the incidence of heart disease, though whether this is simply because it rids the blood of excess lipids or because of its stimulant effect is unknown.

Laxative/diuretic
Coffee is also a powerful stimulant for peristalsis and is sometimes considered to prevent constipation; it is also a diuretic. However, coffee can also cause loose bowel movements.

Practitioners in alternative medicine often recommend coffee enemas for "cleansing of the colon" due to its stimulus of peristalsis, although mainstream medicine has not proved any benefits of the practice.

Antioxidant
Coffee contains the anticancer compound methylpyridinium. This compound is not present in significant amounts in other food materials. Methylpyridinium is not present in raw coffee beans but is formed during the roasting process from trigonelline, which is common in raw coffee beans. It is present in both caffeinated and decaffeinated coffee, and even in instant coffee.

Prevention of dental caries
The tannins in coffee may reduce the cariogenic potential of foods. In vitro experiments have shown that these polyphenolic compounds may interfere with glucosyltransferase activity of mutans streptococci, which may reduce plaque formation. In rat experiments, tea polyphenols reduced caries.

Gout
Coffee consumption decreased risk of gout in men over age 40. In a large study of over 45,000 men over a 12-year period, the risk for developing gout in men over 40 was inversely proportional with the amount of coffee consumed.

Risks
Many notable effects of coffee are related to its caffeine content. Amongst other known negative health associations it is not clear whether these are due to the caffeine or other unidentified compounds (suggesting that these may be modified by switching to decaffeinated coffee).

Anxiety and sleep changes
Many coffee drinkers are familiar with "coffee jitters", a nervous condition that occurs when one has had too much caffeine. It can also cause anxiety and irritability, in some with excessive coffee consumption, and some as a withdrawal symptom. Coffee can also cause insomnia in some, while paradoxically it helps a few sleep more soundly.

Constipation
Due to its diuretic effect, coffee use can lead to dehydration in some individuals, and as a result, contribute to constipation.

Cosmetic
Like tea, coffee causes staining of the teeth.

Cholesterol
Coffee brewed using a French press method contains oils otherwise trapped by more commonly used paper filters. These oils have been shown to significantly raise LDL cholesterol levels. The risk is not present in paper filtered coffee.

Blood pressure
A recent study by Harvard Med that set out to prove that the caffeine in coffee would put people at risk for high blood pressure ended up rejecting the theory. 155,000 nurses were followed for 12 years and the results showed that large amounts of coffee did not induce a "risky rise in blood pressure". As a note, this study did not include men.

Effects on pregnancy and menopause
A February 2003 Danish study of 18,478 women linked heavy coffee consumption during pregnancy to significantly increased risk of stillbirths (but no significantly increased risk of infant death in the first year). "The results seem to indicate a threshold effect around four to seven cups per day," the study reported. Those who drank eight or more cups a day (64 U.S. fl oz or 1.89 L) were at 220% increased risk compared with nondrinkers. This study has not yet been repeated, but has caused some doctors to caution against excessive coffee consumption during pregnancy.

There are also gender-specific effects: in some PMS sufferers it increases the symptoms; it can reduce fertility in women; it may increase the risk of osteoporosis in postmenopausal women; and there may be risks to a fetus if a pregnant woman drinks 8 or more cups a day (48 U.S. fl oz or 1.4 L or more).

Decaffeinated coffee is occasionally regarded as a potential health risk to pregnant women, due to the high incidence of chemical solvents used to extract the caffeine. These concerns have almost no basis, however, as the solvents in question evaporate at 80–90 °C, and coffee beans are decaffeinated before roasting, which occurs at approximately 200 °C. As such, these chemicals, namely trichloroethane and methylene chloride, are present in trace amounts at most, and neither pose a significant threat to unborn children.

Coronary artery disease
A 2004 study tried to discover why the beneficial and detrimental effects of coffee conflict. The study concluded that consumption of coffee is associated with significant elevations in biochemical markers of inflammation. This is a detrimental effect of coffee on the cardiovascular system, which may explain why coffee has so far only been shown to help the heart at levels of four cups (20 fl oz or 600 mL) or fewer per day.

The health risks of decaffeinated coffee have been studied, with varying results. One variable is the type of decaffeination process used; while some involve the use of organic solvents which may leave residual traces, others rely on steam.

A study has shown that cafestol, a substance which is present in boiled coffee drinks, dramatically increases cholesterol levels, especially in women. Filtered coffee contains only trace amounts of cafestol.

Polymorphisms in the CYP1A2 gene may lead to a slower metabolism of caffeine. In patients with a slow version of the enzyme the risk for myocardial infarction is increased by a third (2-3 cups) to two thirds (>4 cups). The risk was more marked in people under the age of 59.

A Harvard study over 20 years of 128,000 people published in 2006 concluded that there was no evidence to support the claim that coffee consumption itself increases the risk of coronary heart disease. The study did, however, show a correlation between heavy consumption of coffee and higher degrees of exposure to other coronary heart disease risk factors such as smoking, greater alcohol consumption, and lack of physical exercise. The results apply only to coffee filtered through paper filters, which excludes boiled coffee and espresso, for example. Additionally, the lead researcher on this study acknowledged that subsets of the larger group may be at risk for heart attack when drinking multiple cups of coffee a day due to genetic differences in metabolizing caffeine.

The Iowa Women's Health Study showed that women who consumed coffee actually had fewer cardiovascular disease incidents and lower cancer rates than the general population. For women who drank 6 or more cups, the benefit was even greater. However, this study excluded 35% of its original participants who already had cardiovascular disease and other chronic diseases when the study began. Since participants were all over the age of 55, no good conclusion can be drawn about the long term effect of coffee drinking on heart disease from this study.