Is coffee a health benefit or a health risk?

Benefit

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by Stephen Janowsky

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Coffee has been consumed for centuries, in spite of repeated attempts to prohibit its use for moral, economic, medical or political reasons. It was discovered in the 9th century in Arabia and it was cultivated for the first time in Ethiopia. In the 15th century, the technique of toasting and grinding coffee grains was developed and the consumption of coffee quickly expanded worldwide.

Coffee is the dried mature seed of Coffea arabica. It is the product that contains the highest amount of caffeine in the diet (0.8-1.8%). The dose of caffeine in coffee depends on genetic differences between grains, as well as on the time and the form of preparation, varying between 30 and 175 mgs by 150 ml. Decaffeinated coffee contains between 2 and 8 mgs by 150 ml. Caffeine, as well as theobromine and theophylline, is a methyl-derivative of xanthine, which is itself a purine-derivative. It is included in the pharmacological group of psychostimulants.

Cof fee intake has many effects on various organs and systems:
- Central nervous system. Caffeine induces a generalized activation of the central nervous system, in a dose-dependant manner, possibly by enhancing the release of noradrenaline. It increases the alert, reduces the sensation of fatigue, it stimulates the capacity to maintain intellectual effort, and maintains the state of wakefulness in spite of sleep deprivation. In addition, caffeine has an invigorating action by means of dopamine release in the limbic system. Caffeine also has an analgesic effect, being sometimes used as an adjuvant in analgesia. It produces blood vessel constriction in the brain, which makes it an effective treatment for migraine. On the other hand, caffeine abuse can cause anxiety, panic attacks, nightmares, and dependency.
- Respiratory system. Methyl-xanthines, especially theophylline, stimulate the respiratory nervous center, dilate the airways, and slightly improve the respiratory function, by increasing the force of contraction of the diaphragm muscle. Therefore, these substances are useful in asthma and other chronic or acute respiratory diseases. They are also first choice drugs in the treatment of apnea in the premature newborn.
- Cardiovascular. Caffeine administration increases the arterial pressure, the heart rate and the heart pumping capacity. However, caffeine ingestion has not been directly linked to hypertension risk, and it does not induce rhythm disturbances, except at very high doses. Most large prospective cohort studies have not found high intakes of coffee or caffeine to increase the risk of coronary heart disease or myocardial infarction (Popkin et al., 2006). On the contrary, in Dutch women, coronary artery calcification was significantly reduced by 60% for moderate (4 cups) and by 46% for high (over 4 cups) coffee intake, compared with a daily intake of 3 cups or less (van Woudenbergh et al., 2008).
- Kidneys. Caffeine has a mild, but durable diuretic effect. However, caffeine consumption of up to 500 mg/day does not cause dehydration or chronic water imbalance; coffee's fluid content compensates for the acute diuretic effect.
- Musculoskeletal. Caffeine boosts the physical energy, by increasing the blood flow to the muscles, the muscular response to nervous stimuli, and by diminishing weariness and fatigue. In the past years, caffeine was forbidden in sports and "doping" was considered if 12 mcg/mL in urine were exceeded. (To yield a positive result, it would be necessary to drink 7 or 8 cups of coffee and pick up a sample 2 to 3 hours later.) Since 2004, caffeine is no longer listed among prohibited substances in sports and thus it can be consumed without restriction.
- Digestive. Caffeine stimulates the contractions of the gallbladder, relaxes the smooth muscles of the biliary tract, and stimulates gastric acid secretion, thus helping digestion. Coffee drinking is unlikely associated with gastric or duodenal ulcers, but it can exacerbate gastroesophageal reflux.
- Lipid metabolism. The consumption of boiled unfiltered coffee has been found to increase plasma total and LDL-cholesterol concentrations, whereas the consumption of filtered coffee does not appear to have adverse effects on lipid profiles. The diterpenes cafestol and kahweol have been identified as cholesterol-raising factors in roasted coffee beans. Diterpenes are extracted by hot water when coffee is brewed, and they are trapped by paper filters. Consequently, filtered coffee contains very little cafestol and kahweol, whereas boiled coffee and espresso may contain significant amounts.
- Pregnancy. Moderate caffeine consumption during pregnancy does not increase the risk of miscarriage and low birth weight, however such risks can be induced by excessive coffee intake. Therefore, pregnant women are often advised to limit caffeine consumption.

Coffee drinking has also been related with health benefits, by possibly preventing chronic conditions like diabetes, Parkinson's and other neurological disorders, and cancer.

Diabetes. In short-term studies, caffeine has been shown to increase insulin levels, reduce insulin sensitivity, and increase cortisol levels (MacKenzie et al., 2007). On the other hand, most epidemiological studies (there are fourteen, at least) confirm a protective effect of coffee against type 2 diabetes, with some dose-response in function of the degree of daily consumption. The observed effect is rather impressive (the risk is reduced by 30 to 60 percent) and is present whatever the type of population. It appears equal, or even greater, with decaffeinated coffee as compared to regular coffee (Legrand & Scheen, 2007). For example, in Japan, coffee drinking was related with a reduction in the prevalence of metabolic syndrome (i.e. a cluster of disorders, including obesity, hypertension, glucose intolerance, and lipid abnormalities) (Hino et al., 2007) and diabetes; those who drink at least 3 cups have 42% less diabetes than those who drink less than 1 cup a day (Iso et al., 2006). The protective effect cannot be attributed exclusively to caffeine, but rather it should be explained by other coffee components, most probably chlorogenic acid and/or quinides, which may posess antioxidant and weight-losing properties (Greenberg et al., 2006). However, the precise mechanism explaining the protection of coffee against type 2 diabetes and its potential relevance in public health remain to be specified.

Neurologic al and psychiatric disorders. Coffee and caffeine consumption have been consistently associated with significant reductions in the risk of Parkinson's disease. For instance, among 30,000 Finnish men and women, coffee drinkers had a 47% (with 1-4 daily cups) to 60% (with 5 or more daily cups) lower risk of developing the disease than non-drinkers (Hu et al., 2007). Similarly, an American study found that high caffeine intake reduces the risk of Parkinson's disease by 42% (Hancock et al., 2007). It has also been suggested that caffeine may be useful for preventing other neuro-degenerative disorders, like Alzheimer's and Huntington's. In Finland again, high coffee intake was found to be associated with less stroke from brain infarction (Larsson et al., 2008). Finally, two prospective cohort studies in the United States found a significant decrease in suicide risk with coffee consumption (Klatsky et al., 1993; Kawachi et al., 1996).

Cancer. Caffeine displays suppressor effects on malignant cells in experimental metastases (Porta et al., 2003). In a Japanese study (Lee et al., 2007), women who regularly consumed 3 or more cups of coffee per day had a 56% lower risk of developing bowel cancer than those who almost never consumed coffee. However, no similar association was found in men. In Italy, the risk of liver cancer decreased for increasing levels of coffee intake (this being true for regular coffee but not for decaffeinated coffee). On the other hand, the existing studies failed to point out any significant association between coffee drinking and the occurrence of ovarian, breast, pancreas or renal cancers.

According to some research, coffee has shown a reduced risk of death with moderate (1 to 4 cups/day) drinking (Woodward, 1999; Kleemola, 2000; Iwai, 2002; Jazbec, 2003). For example, in a study which included Japanese men (4079 years), those who consumed 2+ cups/day of coffee had a 57% lower mortality risk compared with those who consumed less than 1/2 cup/day (Iwai, 2002). No statistically significant effect was seen in women. In a Californian study (Paganini-Hill, 2007) of 8,600 women and 5,000 men with a mean age of 74, followed for 23 years, caffeine consumption exhibited a U-shaped mortality curve. Moderate caffeine consumers had a significantly reduced risk of death compared to low- or non-consumers. In contrast, other studies have found no association of coffee consumption and mortality (Dawber, 1974; Yano, 1977; Heyden, 1978; Klatsky, 1993; Jazbec, 2003; Mukamal, 2004) or a slightly increased risk (Lindsted, 1992).
Coffee contains many different chemical compounds and no certainty exists as to which ones may be associated with disease risk. Antioxidants like chlorogenic and caffeic acids may reduce mortality by decreasing the incidence of cardiovascular disease (Steinberg, 2002), cancer (van Poppel, 1997), and dementia (Deschamps, 2001).

In conclusion, coffee drinking stimulates the nervous system, increases the physical capacity, and improves breathing. It is useful for the treatment of migraine. It does not induce chronic hypertension, heartbeat abnormalities, or coronary heart disease. In addition, regular coffee intake might prevent diabetes, neurological disorders, cancer, and decrease mortality. Therefore, if abusive consumption is avoided, coffee can be considered a healthy beverage.

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