Coffee Risks
Caffeine dependency
- Main article: Health effects of caffeine
Cancer
Over 1,000 chemicals have been reported in roasted coffee, and 19 are known rodent carcinogens;[53] however, most substances cited as rodent carcinogens occur naturally and should not be assumed to be carcinogenic in humans at exposure levels typically experienced in day-to-day life.[53] However, whole coffee extract is suspected to cause cancer of the human pancreas,[54] and there is limited evidence of a weak positive relationship between coffee consumption and bladder cancer in humans.[55] However, more recent follow-up studies to the 1981 study linking coffee consumption to pancreatic cancer have not found any link between coffee consumption and pancreatic cancer.[56] A recent meta-analysis based on 37 case-control and 17 cohort studies (10,594 cases)[57] provided quantitative evidence that coffee consumption was not appreciably related to pancreatic cancer risk, even at high intakes. No significant association between coffee consumption and the risk of gastric and/or pancreatic cancers was found in a more recent prospective study.[58]Instant coffee contains a much higher level of acrylamide than brewed coffee.[37]
Gastrointestinal problems
Coffee can damage the lining of the gastrointestinal organs, causing gastritis and ulcers. The consumption of coffee is therefore not recommended for people with gastritis, colitis, and ulcers.[59]Psychological effects 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.[60] Coffee can also cause insomnia in some. In others it can cause narcolepsy.[61] However an analysis of the Nurses' Health Study concluded depression rates among women decreased with increased consumption of caffeinated coffee.[62]Caffeine, a major component of coffee, has various psychological effects. A study from Johns Hopkins Medical School suggests that the perceived psychological benefits of caffeine are merely the result of eliminating withdrawal symptoms.[63] The author of Emotional Intelligence 2.0 suggests that chronic caffeine consumption can lead to a decrease in emotional intelligence.[63]
Cholesterol
A 2007 study by the Baylor College of Medicine indicates that the diterpenes cafestol and kahweol, found only in coffee beans, may raise levels of low-density lipoprotein or LDL in humans.[64] This increase in LDL levels is an indicator that coffee raises cholesterol. The Baylor study suggests a possible link between cafestol, kahweol and higher levels of cholesterol in the body.Paper coffee filters have a property that binds to lipid-like compounds which allows the filter to remove most of the cafestol and kahweol found in coffee. Brew methods which do not use a paper filter, such as the use of a press pot, do not remove cafestol and kahweol from the final brewed product.[65][66]
Blood pressure
Caffeine has previously been implicated in increasing the risk of high blood pressure; however, recent studies on coffee consumption have not confirmed any association.[67] In a 12-year study of 155,000 female nurses, large amounts of coffee did not induce a "risky rise in blood pressure"[68] .[69] Previous studies had already shown statistically insignificant associations between coffee drinking and clinical hypertension. Effect of coffee on morbidity and mortality due to its effect on blood pressure is too weak, and has not been studied. Other positive and negative effects of coffee on health would be difficult confounding factors.[1]Effects on pregnancy
Caffeine molecules are small enough to penetrate the placenta and slip into the baby's blood circulation. Unlike adults, organs and systems in fetuses are not full-fledged, therefore not capable of fully metabolizing caffeine and excreting it. The stimulant tends to linger in the fetus's blood ten times longer than in adults. High levels of caffeine are bound to accumulate in the baby's body with frequent maternal consumption of caffeine. Just like what it does to adults, caffeine could also send the baby's pulse and breathing rate racing and affect its sleep pattern for an extended duration.[70]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.[71]
Decaffeinated coffee is also regarded as a potential health risk to pregnant women when chemical solvents are used to extract the caffeine instead of other less invasive processes.[citation needed] The impact of these chemicals is debated, 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 may not pose a significant threat to embryos and fetuses.[citation needed]
Iron deficiency anemia
Coffee consumption can lead to, but is not the cause of iron deficiency anemia, especially in mothers and infants.[72] Coffee also interferes with the absorption of supplemental iron.[73] 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.[47]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 (24 fl oz or 600 mL) or fewer per day.[74]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.[citation needed]
A study has shown that cafestol, a substance which is present in boiled coffee drinks, increases serum 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 (heart attack) 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.[75]
A Harvard study conducted over the course of 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.[76] 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.[citation needed]
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.[77]
