Worried about your heart? Is the grim specter of liver cancer keeping you up at night? That morning cup of joe (or five or six) just might be what the doctor ordered.
New research has added to a growing body of evidence that coffee has substantial health benefits. Among the latest findings: Caffeine prevents the development of multiple sclerosis-like symptoms in mice; higher coffee intake is inversely related to the risk of developing liver cancer and, best of all, coffee drinkers have a lower death rate than those who abstain.
It's enough to make one wonder: Is coffee the elixir of life?
For now, at least, most researchers won't go that far, although they agree that coffee's old reputation for being bad for you is largely underserved. It's now recognized that in addition to caffeine, coffee is chock-full of potent antioxidant compounds.
"I don't think of coffee as an overall health food," said Dr. Arthur L. Klatsky, a California physician who has studied coffee's health effects for decades. Coffee's apparent benefits come with some drawbacks. It has been linked to miscarriages and benign breast disease, Klatsky said, yet it also seems to prevent Parkinson's disease and is associated with a lower risk of suicide.
A report last month in the Annals of Internal Medicine showed that coffee drinkers had a slightly lower death rate, mostly due to fewer cases of cardiovascular disease. Researchers followed 86,214 middle-aged women in the Nurses' Health Study and a slightly younger group of 41,736 male doctors, dentists and pharmacists in the Health Professionals Follow-Up Study.
After adjusting for age, smoking and other known cardiovascular and cancer risks, researchers noticed there had been fewer deaths among those who drank more coffee (subjects ranged from those who drank one cup or fewer a month to people downing six cups a day). The more coffee a person drank, the lower the risk of death. It didn't matter whether they were drinking regular or decaf.
"This study supports the hypothesis that coffee consumption may have beneficial effects on health," said Esther Lopez-Garcia, an epidemiologist at Universidad Autónoma de Madrid, who led the study with collaborators from the Harvard School of Public Health. "At this point, coffee is considered not detrimental for health among healthy people — that is, if you don't suffer from insomnia or anxiety or if you don't have high blood pressure."
The results make sense, given that coffee is known to improve the functioning of the endothelium, the thin layer of cells lining our blood vessels, Lopez-Garcia said. "Compounds in coffee like chlorogenic acid, ferulic acid and p-coumaric acid have a strong antioxidant capacity, which reduces the risk of endothelial dysfunction," she said. Other compounds in coffee improve insulin sensitivity, reducing the risk of Type 2 diabetes.
The participants mainly drank American-style filtered coffee, not boiled coffees, like French press or espresso, Lopez-Garcia said. Paper filters strain out cafestol and kahweol, fat-soluble compounds in coffee thought to raise levels of low-density lipoprotein (LDL), the so-called "bad cholesterol."
The new research challenges Klatsky's study of 129,000 Kaiser Permanente managed care patients in the San Francisco Bay Area. "We have found no overall benefit" from coffee, Klatsky said. But he said the new results are intriguing and warrant more investigation.
Lopez-Garcia agreed: "We need to replicate these results in other different populations, in people with chronic diseases, and to assess the effect of other types of coffee on health. Evidence from our study is still insufficient to recommend drinking coffee on a health basis. Our results on the potential protective effect of coffee should still be confirmed by future studies."
Meanwhile, a study published June 30 in the Proceedings of the National Academy of Sciences, reported that caffeine protected mice from developing experimental autoimmune encephalomyelitis (EAE), which mimics multiple sclerosis in humans. EAE results when killer T-cells cross the blood-brain barrier into the central nervous system, where they attack neurons, stripping them of their protective myelin sheath. But by blocking the effects of a chemical called adenosine, caffeine prevented the T-cells from entering the central nervous system.
Dr. Steve Prescott, president of the Oklahoma Medical Research Foundation, said one of his researchers, immunologist Linda Thompson, had genetically engineered a strain of mice lacking a critical enzyme called CD 73, which helps produce adenosine, a powerful anti-inflammatory. Thompson and her collaborators at Cornell University and Finland's University of Turku predicted the mice would develop EAE, and were surprised when that turned out not to be the case, Prescott said.
Forced to rethink CD 73's role in EAE, they realized that the adenosine-blocking function of caffeine might offer a way to prevent the disease in normal mice.
Prescott cautions that drinking more coffee might not protect humans from MS.
"I don't really think that drinking coffee at the level necessary to do this would be the solution," he says. "It points the way to a signaling pathway, which is one of the main things you look for in developing pharmaceuticals."
There are some concerns associated with coffee, mostly related to the stimulatory effects of caffeine. Klatsky mentioned that caffeine has been implicated in benign breast disease (but not breast cancer) and can cause palpitations, dyspepsia and insomnia. "The nervous system effects are largely caffeine," he said.
Other studies have looked at a possible increased risk of osteoporosis in postmenopausal women and increased blood levels of homocysteine, which has been implicated in cardiovascular disease. Nonetheless, coffee comes across as fairly benign.
And its beneficial effects may extend beyond the nervous system to the liver. The July issue of Hepatology, the journal of the American Association for the Study of Liver Diseases, included a study of 60,323 Finnish participants in which researchers found there was a "significant inverse association between coffee drinking and the risk of primary liver cancer."
Seeking to explain their findings, the researchers said, "Several previous studies have found an inverse association between coffee drinking and the risk of chronic liver disease and liver cirrhosis, which are strongly related to the risk of liver cancer. Therefore, it could be hypothesized that coffee drinking might decrease liver cancer risk partly through coffee's protective effect on the risk of chronic liver disease."
In an accompanying editorial, Italian epidemiologist Carlo La Vecchia wrote, "It remains difficult, however, to translate the inverse relation between coffee drinking and liver cancer risk observed in epidemiological studies into potential implications for prevention of liver cancer by increasing coffee consumption."
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