Heart disease: The effect of coffee on your heart

There seems to be no end to the flow of research money when it comes to funding studies about coffee. This week, for instance, I came across an Australian study that found coffee drinkers to be more likely to agree with a persuasive presentation when compared to non-caffeinated subjects. 
 
I suppose that study provides a practical use in the real world. If you're trying to close a sale or asking your boss for a pay rise, a couple of espresso shots might tip the deal in your favour.
But even more useful are some recent studies that help illuminate the effect coffee has on the risk of heart attacks and heart disease.  
 

Coffee and heart health: The caffeinated heart

 
Last year, a Greek study caught some media attention with the finding that caffeine intake might increase the risk of aortic stiffness, which in turn could raise the risk of heart disease. But just last month, coffee lovers who fear for their heart received some better news in the journal Circulation. 
 
US Researchers at the Harvard School of Public Health analysed data from the Health Professionals Follow-Up Study and the Nurses Health Study. After medical records and questionnaires detailing coffee consumption for more than 120,000 subjects were examined, researchers found that people who drank as much as five cups of coffee each day had no greater coronary heart disease risk than subjects who drank less than one cup of coffee per month. 
 
On the heels of that research, the May 2006 issue of the American Journal of Clinical Nutrition had an even more encouraging report: Coffee might actually protect the heart. 
 
Researchers at the University of Minnesota (UM) in the US followed a study design similar to that used by the Harvard team. The Iowa Women's Health Study provided 15 years of data on more than 27,000 women over the age of 55. When medical records for subjects who didn't drink coffee were compared to those who drank from one to three cups per day, subjects in the latter group had a 24 percent reduction in the risk of death due to cardiovascular disease. 
 
One of the authors of the study, Dr. David R.
Jacobs, Jr., attributed coffee's apparent protective effect to a reduction of inflammation.
In an interview with Reuters Health, Dr. Jacobs cited previous studies that have shown coffee to be a primary source of anti-inflammatory antioxidants for many people.  
 

Coffee and heart health: Fast vs. slow

 
As promising as the Harvard and UM studies are, they don't close the door on the question of how caffeine intake affects the heart. In fact, the key to the way a cup of coffee affects you personally may be found in your liver. 
 
In a March 2006 study that appeared in the Journal of the American Medical Association, researchers at the University of Toronto (UT) in Canada note that caffeine is metabolised by an enzyme in the liver known as CYP1A2. But the speed at which this enzyme metabolises caffeine depends on the variation of a gene. If you have one type of this gene, your liver will metabolise caffeine rapidly.
Slow caffeine metabolism will result if you have the other variation. 
 
In the UT study, researchers tested more than 4,000 subjects to determine which gene variation they had. Half the subjects had experienced one heart attack, and the other half of the cohort had no known cardiovascular problems. A food frequency questionnaire was used to assess coffee intake. 
 
The results: Those who metabolised caffeine slowly were at greater risk of suffering a heart attack compared to subjects who metabolised caffeine quickly. The risk was especially pronounced for younger coffee drinkers. Slow caffeine metabolising subjects under the age of 59 who drank two to three cups of coffee daily had 67 percent greater risk of heart attack compared to quick metabolisers. And the more coffee consumed by this group, the higher the risk of heart attack. 
 
Getting tested for this particular gene variation is impractical. But if you've ever displayed a sensitivity to caffeine intake, that may be an indication that your liver - and ultimately, your heart - could be overtaxed by a steady flow of caffeinated beverages. 

Sources:

'Coffee Consumption and Coronary Heart Disease in Men and Women' Circulation, Vol. 113, May 2006, ahajournals.org 'Consumption of Coffee is Associated with Reduced Risk of Death Attributed to Inflammatory and Cardiovascular Diseases in the Iowa Women's Health Study' American Journal of Clinical Nutrition, Vol. 83, No. 5, May 2006, ajcn.org 'Antioxidant-Rich Coffee May Have Health Benefits'
Megan Rauscher, Reuters Health, 5/19/06, reutershealth.com 'Coffee, CYP1A2 Genotype, and Risk of Myocardial Infarction' Journal of the American Medical Association, Vol. 295, No. 10, 3/8/06, jama.ama- assn.org 'Vitamin C Depletion Correlates With Lower Body Fat, Not Weight Loss During Short-Term Diet'
Eureka Alert, 4/3/06, eurekalert.org