BETHESDA, MD — Moderate tea drinking can help to slow progression of coronary artery calcium and reduce the risk of cardiovascular events, but coffee intake may have a neutral effect, according to new research.
"We found that being a regular tea drinker was associated with a lower prevalence and progression of coronary artery calcium and a lower incidence of cardiovascular events," first author Dr P Elliott Miller (National Institutes of Health) told heartwire from Medscape. "In contrast, we found a neutral association between regular coffee and caffeine intake with coronary artery calcium and incident cardiovascular outcomes.
"Our study supports regular tea consumption as part of a heart-healthy diet as recommended by the American Heart Association," he said.
"Several studies have looked at coffee or tea and different cardiovascular outcomes. Typically, it will just be tea or coffee and the presence or absence of coronary artery calcium, or progression, or just outcomes. The benefit of our study is we've looked at all three of them in the same group, which is helpful to establish more than just a casual relationship. That's one of the strengths," Miller said.
Another strength is the multiethnic cohort of the study, he said.
The results were published online September 15, 2016 in the American Journal of Medicine.
Miller and colleagues analyzed data on more than 6500 ethnically diverse individuals involve in the Multi-Ethnic Study of Atherosclerosis (MESA), a population-based study into the prevalence, risk factors, and progression of subclinical cardiovascular disease.
Men and women 44 to 84 years old (women 52.9%) at six university health centers completed food frequency questionnaires, reporting the frequency of coffee and black or green tea intake on a range of never to six or more cups a day.
More than half the participants (57.6%) reported never drinking tea, while 29.5% reported drinking less than one cup a day and 12.9% drank one or more cups a day.
About half the participants (50.9%) reported drinking one or more cups of coffee a day, while 25% drank zero cups and 24% drank less than one cup a day.
Researchers collected cardiovascular-event data through telephone interviews every 9 to 12 months during follow-up.
The researchers found the prevalence of coronary artery calcium to be zero in 49.9% of participants, 1 to 99 in 26.5%, and 100 or higher in 23.6%. They found the incidence of all cardiovascular events and hard cardiovascular events to be 10.8 and 7.5 per 1000 person-years, respectively, over a median follow-up of 11.1 years.
In adjusted multivariable models, participants who drank one or more cups of tea a day had a lower prevalence of coronary artery calcium scores of 100 or higher compared with people who drank no tea (relative risk 0.64). People who drank one or more cups of tea a day also had reduced progression of coronary artery calcium (RR 0.73).
"Coronary artery calcium is a marker of subclinical disease," Miller told heartwire in a telephone interview. "If it's really low, a patient's future risk is also very low for having a cardiovascular event. If it's high, it suggests that that person already has a fair amount of coronary disease.
"In the study it was a marker of how much disease at baseline and how disease progressed over time," he added. "It can be highly predictive. If have a patient who is medium risk, you can use the coronary calcium score to differentiate: Is this patient more of a high risk or more of a low risk?"
Participants who reported drinking less than one cup of coffee a day had an increased incidence of cardiovascular events compared with people who drank no coffee (hazard ratio [HR] 1.28, 95% CI 1.02–1.61).
The researchers found tea intake of one or more cups a day to be associated with a lower incidence of cardiovascular events, compared with no tea intake (HR 0.71, 95% CI 0.53–0.95).
"The mechanism for tea is anyone's guess, but my best guess would be the antioxidants that are found in tea," Miller said. "There's pretty good evidence that flavonoids found in tea can be beneficial for coronary disease."
They found coffee and overall caffeine intake not to be associated with cardiovascular events.
"Every study sees different things for coffee. Most studies have seen either a neutral or potentially beneficial effect of coffee," Miller said. "It's possible that the numbers in our study are just not high enough to see the potential benefit.
"Physicians are often asked by patients with and without coronary disease whether it is safe to drink caffeinated beverages. Our results suggest there may be a beneficial effect of tea on cardiovascular disease and a neutral effect of coffee, suggesting that regular use is safe for patients," Miller told heartwire.
"The majority of research on coffee and tea with cardiovascular disease has been completed with food questionnaires, as was our study, which relies on patient recall. Future research should leverage technology such as medical apps to more accurately gauge coffee and tea intake in relation to cardiovascular outcomes," he said.
"It is important to mention that this is an observational study and we cannot say for sure it was the tea or just the healthier lifestyle of the tea drinkers," he added.
The National Heart, Lung, and Blood Institute supported this research. The authors reported no relevant financial relationships.
Heartwire from Medscape © 2016 Medscape, LLC
Cite this: Moderate Tea Drinking May Slow CAC Progression, Cut CV Event Risk: MESA - Medscape - Sep 23, 2016.