Friday, December 5, 2014

Coffee Consumption: Heart Attack and Stroke Benefits

Higher coffee consumption is inversely associated with risk of CVD and stroke in the general population.

Coffee is one of the most extensively researched components in the diet. New studies are regularly being added to the already large body of scientific research, which overall suggests that moderate habitual coffee consumption is not associated with detrimental effects on cardiovascular health

Among recent studies, a new review paper1 highlights that for most healthy people, moderate coffee consumption is unlikely to adversely affect cardiovascular health. Furthermore a new paper2 concluded that higher green tea and coffee consumption is inversely associated with risk of CVD and stroke in the general population.

Considerable research has also been devoted to investigating associations between coffee consumption and key risk factors for cardiovascular disease, such as hypertension (high blood pressure) and elevated cholesterol. Most evidence suggests that regular moderate consumption of caffeinated coffee has no long-term effect on blood pressure and does not increase the risk of hypertension.

A recent study suggests that moderate consumption of paper-filtered coffee may have an unfavourable effect on plasma cholesterol3. The wider body of evidence indicates that the impact of coffee on cholesterol is dependent on the brewing method. Unfiltered coffee raises serum cholesterol levels whereas this is not the case with filter coffee because the cholesterol-raising compounds in coffee are retained in the paper filter.

Throughout 2013 coffee and mortality has been a subject of several scientific research papers, which have produced conflicting results. One study4 found a 21% increase in mortality rate in those drinking more than 28 cups of coffee a week. However recent data from a meta-analysis and systematic review5 assessed 23 studies and concluded that coffee consumption is, in fact, inversely related to the risk of mortality.


1 Rebello S.A. & van Dam R.M. (2013) Coffee Consumption and Cardiovascular Health: Getting to the Heart of the Matter. Current Cardiology Reports, 15:403.

2 Kokubo Y. et al. (2013) The Impact of Green Tea and Coffee Consumption on the Reduced Risk of Stroke Incidence in Japanese Population: The Japan Public Health Center-Based Study Cohort. Stroke, published online ahead of print.

3 Correa T.A.F. et al. (2013) Paper filtered coffee increases cholesterol and inflammation biomarkers independent of roasting degree. Nutrition, 29(7-8):977-81.

4 Liu J. et al. (2013) Association of coffee consumtpion with all-cause and cardiovascular disease mortality. Mayo Clinic Proceedings, published online ahead of print.

5 Malerba S. et al. (2013) A meta-analysis of prospective studies of coffee consumtpion and mortality for all causes, cancers and cardiovascular disease. European Journal of Epidemiology, 28(7):527-539.

Coffee may help perk up your blood vessels

The caffeine in a cup of coffee might help your small blood vessels work better, according to research presented at the American Heart Association's Scientific Sessions 2013.

A study of 27 healthy adults showed – for the first time – that drinking a cup of caffeinated coffee significantly improved blood flow in a finger, which is a measure of how well the inner lining of the body's smaller blood vessels work. Specifically, participants who drank a cup of caffeinated coffee had a 30 percent increase in blood flow over a 75-minute period compared to those who drank decaffeinated coffee.

"This gives us a clue about how coffee may help improve cardiovascular health," said Masato Tsutsui, M.D., Ph.D., lead researcher and a cardiologist and professor in the pharmacology department at the University of the Ryukyus in Okinawa, Japan.

The study adds to a growing body of research about coffee, the most widely consumed beverage worldwide. Previous studies showed that drinking coffee is linked to lower risks of dying from heart disease and stroke, and that high doses of caffeine may improve the function of larger arteries.

Study participants were people who did not regularly drink coffee, ranging in age from 22 to 30. On one day, each participant drank one five-ounce cup of either regular or decaffeinated coffee. Then researchers measured finger blood flow with laser Doppler flowmetry, a non-invasive technique for gauging blood circulation on a microscopic level. Two days later, the experiment was repeated with the other type of coffee. Neither the researchers nor the participants knew when they were drinking caffeinated coffee.

The researchers noted blood pressure, heart rate, and vascular resistance levels. They also took blood samples to analyze levels of caffeine and to rule out the role of hormones on blood vessel function.

Compared to decaf, caffeinated coffee slightly raised participants' blood pressure and improved vessel inner lining function. Heart rate levels were the same between the two groups.

Moderate coffee consumption offers protection against heart failure

While current American Heart Association heart failure prevention guidelines warn against habitual coffee consumption, some studies propose a protective benefit, and still others find no association at all. Amidst this conflicting information, research from Beth Israel Deaconess Medical Center attempts to shift the conversation from a definitive yes or no, to a question of how much.

"Our results did show a possible benefit, but like with so many other things we consume, it really depends on how much coffee you drink," says lead author Elizabeth Mostofsky, MPH, ScD, a post-doctoral fellow in the cardiovascular epidemiological unit at BIDMC. "And compared with no consumption, the strongest protection we observed was at about four European, or two eight-ounce American, servings of coffee per day."

The study published in the journal Circulation: Heart Failure, found that these moderate coffee drinkers were at 11 percent lower risk of heart failure.

Data was analyzed from five previous studies – four conducted in Sweden, one in Finland – that examined the association between coffee consumption and heart failure. The self-reported data came from 140,220 participants and involved 6,522 heart failure events.

In a summary of the published literature, the authors found a "statistically significant J-shaped relationship" between habitual coffee consumption and heart failure, where protective benefits begin to increase with consumption maxing out at two eight-ounce American servings a day. Protection slowly decreases the more coffee is consumed until at five cups, there is no benefit and at more than five cups a day, there may be potential for harm.

It's unclear why moderate coffee consumption provides protection from heart failure, but the researchers say part of the answer may lie in the intersection between regular coffee drinking and two of the strongest risk factors for heart failure – diabetes and elevated blood pressure.

"There is a good deal of research showing that drinking coffee lowers the risk for type 2 diabetes, says senior author Murray Mittleman, MD, DrPH, a physician in the Cardiovascular Institute at Beth Israel Deaconess Medical Center, an Associate Professor of Medicine at Harvard Medical School and director of BIDMC's cardiovascular epidemiological research program. "It stands to reason that if you lower the risk of diabetes, you also lower the risk of heart failure."

There may also be a blood pressure benefit. Studies have consistently shown that light coffee and caffeine consumption are known to raise blood pressure. "But at that moderate range of consumption, people tend to develop a tolerance where drinking coffee does not pose a risk and may even be protective against elevated blood pressure," says Mittleman.

This study was not able to assess the strength of the coffee, nor did it look at caffeinated versus non-caffeinated coffee.

"There is clearly more research to be done," says Mostofsky. "But in the short run, this data may warrant a change to the guidelines to reflect that coffee consumption, in moderation, may provide some protection from heart failure."

Coffee = Reduced Risk of Heart Rhythm Disturbances

Coffee drinkers may be less likely to be hospitalized for heart rhythm disturbances, according to a study by the Kaiser Permanente Division of Research in Oakland, Calif. The researchers note that the findings may be surprising because patients frequently report palpitations after drinking coffee.

While it has been established that very large doses of caffeine, the most active ingredient in coffee, can produce rhythm disturbances, there has been limited epidemiologic research about the caffeine doses people take. Previous data from a population study in Denmark compared heavy to light coffee drinkers with respect to risk of atrial fibrillation, the most common major rhythm disturbance, and found no statistically significant difference. This research presentation is believed to be the first large, multiethnic population study to look at all major types of heart rhythm disturbance, the researchers said.

The researchers followed 130,054 men and women and found that those who reported drinking four or more cups of coffee each day had an 18 percent lower risk of hospitalization for heart rhythm disturbances. Those who reported drinking one to three cups each day had a 7 percent reduction in risk, according to Arthur Klatsky, MD, the study's lead investigator and a senior consultant in cardiology at Kaiser Permanente Division of Research in Oakland, Calif.

"Coffee drinking is related to lower risk of hospitalization for rhythm problems, but the association does not prove cause and effect, or that coffee has a protective effect," Klasky said. Other explanations for the association might include other traits of coffee drinkers such as exercise or dietary habits. Additionally, some people with heart rhythm problems often are not hospitalized.

"However, these data might be reassuring to people who drink moderate amounts of coffee that their habit is not likely to cause a major rhythm disturbance," Klatsky said. While this report is not sufficient evidence to say that people should drink coffee to prevent rhythm problems, it supports the idea that people who are at risk for rhythm problems, or who have rhythm problems, do not necessarily need to abstain from coffee, emphasized Klatsky.

The long-term observational study involved 130,054 men and women, 18 to 90 years old, with the majority less than 50 years old. About 2 percent (3,317) were hospitalized for rhythm disturbances; 50 percent of those were for atrial fibrillation, the most common heart rhythm problem. The 18 percent reduction in risk was consistent among men and women, different ethnic groups, smokers and nonsmokers. It also was similar for various rhythm problems such as paroxysmal supraventricular tachycardia, atrial flutter, and atrial fibrillation.

Fourteen percent of the people in the study drank less than one cup of coffee a day; 42 percent drank one to three cups of coffee a day; and 17 percent reported drinking four cups or more each day. Only 27 percent of the people in the study were not coffee drinkers.

While emphasizing that these observational data do not establish causality and a protective mechanism is unclear, researchers speculate that moderate doses of caffeine may affect rhythm disturbances by antagonism of adenosine, a nucleoside compound widely distributed in the body. In the heart adenosine has several effects on conduction of electrical impulses, muscle cell energetics, and heart muscle cell recovery that might predispose to rhythm problems. Caffeine antagonizes adenosine effects by blocking its chemical sites of action.

The researchers examined hospitalization data by elapsed time after the initial examination. For hospitalization within 10 years, the reduction in hospitalizations for people who consumed four cups of coffee or more each day reached 28 percent.

The researchers also studied persons in the group with or without symptoms or history of heart and respiratory disease. For both groups, consuming four cups of coffee daily appeared to be associated with fewer hospitalizations for rhythm disturbances.

Caffeine may prevent heart disease death in elderly

Habitual intake of caffeinated beverages provides protection against heart disease mortality in the elderly, say researchers at SUNY Downstate Medical Center and Brooklyn College.

Using data from the first federal National Health and Nutrition Examination Survey Epidemiologic Follow-up Study, the researchers found that survey participants 65 or more years old with higher caffeinated beverage intake exhibited lower relative risk of coronary vascular disease and heart mortality than did participants with lower caffeinated beverage intake.

John Kassotis, MD, associate professor of medicine at SUNY Downstate, said, "The protection against death from heart disease in the elderly afforded by caffeine is likely due to caffeine's enhancement of blood pressure."_

The protective effect also was found to be dose-responsive: the higher the caffeine intake the stronger the protection. The protective effect was found only in participants who were not severely hypertensive. No significant protective effect was in patients below the age of 65.

Green tea, coffee may help lower stroke risk

Green tea and coffee may help lower your risk of having a stroke, especially when both are a regular part of your diet, according to research published in Stroke: Journal of the American Heart Association.

"This is the first large-scale study to examine the combined effects of both green tea and coffee on stroke risks," said Yoshihiro Kokubo, M.D., Ph.D., F.A.H.A., F.A.C.C., F.E.S.C., lead author of the study at Japan's National Cerebral and Cardiovascular Center. "You may make a small but positive lifestyle change to help lower the risk of stroke by adding daily green tea to your diet."

Researchers asked 83,269 Japanese adults about their green tea and coffee drinking habits, following them for an average 13 years. They found that the more green tea or coffee people drink, the lower their stroke risks.

- People who drank at least one cup of coffee daily had about a 20 percent lower risk of stroke compared to those who rarely drank it.
- People who drank two to three cups of green tea daily had a 14 percent lower risk of stroke and those who had at least four cups had a 20 percent lower risk, compared to those who rarely drank it.
- People who drank at least one cup of coffee or two cups of green tea daily had a 32 percent lower risk of intracerebral hemorrhage, compared to those who rarely drank either beverage. (Intracerebral hemorrhage happens when a blood vessel bursts and bleeds inside the brain. About 13 percent of strokes are hemorrhagic.)
- Participants in the study were 45 to 74 years old, almost evenly divided in gender, and were free from cancer and cardiovascular disease.

During the 13-years of follow-up, researchers reviewed participants' hospital medical records and death certificates, collecting data about heart disease, strokes and causes of death. They adjusted their findings to account for age, sex and lifestyle factors like smoking, alcohol, weight, diet and exercise.

Previous limited research has shown green tea's link to lower death risks from heart disease, but has only touched on its association with lower stroke risks. Other studies have shown inconsistent connections between coffee and stroke risks.

Initial study results showed that drinking more than two cups of coffee daily was linked to increasing coronary heart disease rates in age- and sex-adjusted analysis. But researchers didn't find the association after factoring in the effects of cigarette smoking — underscoring smoking's negative health impact on heart and stroke health.

A typical cup of coffee or tea in Japan was approximately six ounces. "However, our self-reported data may be reasonably accurate, because nationwide annual health screenings produced similar results, and our validation study showed relatively high validity." Kokubo said. "The regular action of drinking tea, coffee, largely benefits cardiovascular health because it partly keeps blood clots from forming." Tea and coffee are the most popular drinks in the world after water, suggesting that these results may apply in America and other countries.

Some chemicals in coffee include chlorogenic acid, thus cutting stroke risks by lowering the chances of developing type 2 diabetes. Further research could clarify how the interaction between coffee and green tea might help further lower stroke risks, Kokubo said.

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