A Healthy Cup of Joe

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A popular mythis that coffee consumption leads to high blood pressure. While this may be true of an acute dose given to a non-coffee drinker, the relationship between coffee and hypertension does not hold for habitual coffee drinkers. According to a report in the Journal of the American Medical Association (Nov 9, 2005), where 155,594 nurses were followed for over 12 years, no linear association was found between caffeinated coffee drinking and hypertension. Interestingly, however, hypertension was associated with the drinking of cola beverages. 

Earlier epidemiological studies conducted in the Scandinavian countries suggested that coffee consumption increases blood cholesterol in humans, but this appears to be due to the way in which coffee is prepared. Scandinavians usually boil their coffee, rather than filter it. Boiled coffee contains two compounds, cafestol and kahweol, not present in filtered coffee, that have been shown to increase blood cholesterol in humans. 

Surprisingly, both epidemiological and experimental studies have demonstrated positive effects of regular coffee drinking on various aspects of health. According to a report in the British Journal of Nutrition (June, 2005), it protects against liver cirrhosis, gallstones and Parkinson's disease, and has in many cases treated hyperactivity in children. Also showing up in the research over the last two years is a relationship between regular coffee drinking and a decreased risk for developing Alzheimer's dementia and diabetes. 

Population studies as far apart as Europe, Japan and the United States have found a relationship between regular coffee use and an increase in glucose tolerance with an associated decrease in diabetes risk. One way this appears to happen is through coffee's ability to block cortisol formation (FEBS Letters, July 2006). Importantly, this effect is only present among long-term coffee drinkers, and is not shown to occur after a dose given to a non-coffee drinker. 

Coffee also increases the production of a hormone (GLP-1) that is responsible for maintaining the responsiveness of beta cells in the pancreas (where insulin is produced) to an increase in blood sugar. But that's not all. Coffee contains an abundance of chlorogenic acid, which delays the absorption of sugar into the blood stream, blunting sugar's toxic effect on beta cell function, and helping to maintain the body's sensitivity to insulin. And the good news for those who are sensitive to caffeine: decaf contains the same active compounds and shows the same diabetic protective effects as regular coffee. 

Studies are also cropping up that indicate long term use of coffee may protect your brain from Alzheimer's dementia. In the case of Alzheimer's, however, caffeine appears to be important. The Byrd Alzheimer's Center and Research Institute in Tampa, Florida decided to find out why. Researchers there fed transgenic mice that had been bred to develop the beta-amyloid pathology seen in Alzheimer's patients 1.5 mg of caffeine daily - the human equivalent of 500 mg, or about 5 cups of coffee per day. 

After long term ingestion of caffeine (we're talking decades in human terms) these mice showed the same ability in tests of learning and memory as normal mice, and did far better than the transgenic control mice. Brain comparisons showed that long term caffeine administration resulted in lower levels of beta-amyloid in the hippocampus (the brain's memory center). The researchers also found that the caffeine-fed mice produced higher levels of adenosine in their brains, which is thought to be involved in the cognitive protection provided by caffeine. 

As is the case with diabetes, long term coffee consumption is protective, not prescriptive. There are no studies showing a reverse in beta-amyloid pathology when caffeine is given after the damage has occurred. Also, elderly patients often do not tolerate caffeine well due to loss of liver enzyme function needed to metabolize it. The amount in a single cup, however, appears to be well tolerated by a majority of elderly people. 

A final caveat is that timing is important. Coffee (including decaf) contains compounds that bind and interfere with the absorption of several other nutrients. These include the minerals calcium, potassium and magnesium, and the B-vitamin, niacin. For this reason I strongly recommend having your cup of Joe between meals.