New research has shown that regular tea consumption can protect against arterial stiffness in the heart - a condition that's been linked to a shortened lifespan and higher risk of cardiovascular disease. 

The study, which looked at habitual and non-habitual tea-drinkers in China, found that those who have been drinking tea regularly for six years or more had the lowest levels of arterial wall thickening and loss of elasticity, and adds to a growing body of evidence that tea consumption is likely doing great things for your heart health.

The team of medical doctors, led by cardiologist Qing-fei Lin from Wuyishan Municipal Hospital in China, surveyed 5,006 male and female people aged 40 to 75 in the local Fujian Province. Of those, 1,564 (31.2 percent) said they were habitual tea-drinkers - defined in the study as having consumed tea once or more per week for at least 12 months.

The subjects were split into four sub-groups: those who have been consuming tea habitually for more than 10 years; habitual tea-drinkers with 6-10 years under their belt; habitual tea-drinkers for 1-5 years; and non-habitual tea-drinkers. 

The researchers measured the brachial-ankle pulse wave velocity (ba-PWV) of their subjects to determine arterial stiffness in both the aorta and peripheral artery of the heart. After adjusting for various lifestyle factors, they found that as the duration and the daily amount of habitual tea consumption increased, the average ba-PWV decreased, which means lower arterial stiffness. 

Characterised by arterial wall thickening and loss of elasticity in both structural and cellular elements of the heart, arterial stiffness has been shown to be a predictor of total mortality and future cardiovascular disease, including heart failure and stroke. You want your arteries to be as flexible as possible to allow for easier blood flow so your heart doesn't have to work so hard.

"Habitual tea consumption may have a protective effect against arterial stiffness, especially for subjects who have habitually consumed tea for more than six years and more than 10 grams daily," the team concludes in the Journal of the American College of Nutrition.

The researchers suspect that the protective effect is due to a chemical reaction that occurs in the endothelial cells inside our arteries when they come into contact with chemicals called catechins - a kind of flavonoid - that are found abundantly in tea (green tea in particular).

"Flavonoids in tea are helpful to relax the blood vessels," Stephen Devries, a preventive cardiologist at Northwestern University, told Deena Shanker at Quartz. "Catechins release nitrous oxide and cause [arteries] to be more compliant."

While the study, which has been published in the Journal of the American College of Nutrition, is limited by the fact that it relies on self-reporting participants to be truthful about their tea consumption history, and focusses only on participants living in a particular region of China, the results reflect what's been found in previous studies from around the world.

"What may have a benefit in one population may not in another population," cardiologist Angela Taylor from the University of Virginia Health System told Shanker. "But studies with tea have been done in almost every ethnic background I can think of."

Back in early 2014, Taiwanese researchers reported in PLOS ONE that drinking a cup of tea per day for one year or more is likely to decrease arterial stiffness, and a 2013 study by the American Journal of Clinical Nutrition concluded that regular tea consumption could lower your risk of stroke. A separate 2007 study by US researchers found that tea-based catechins can improve cardiac structure in as little as 2 hours.

More recently, a meta-analysis of 24 studies on 856,206 individuals published in the European Journal of Epidemiology last year concluded, "increased tea consumption is associated with a reduced risk of coronary heart disease, cardiac death, stroke, cerebral infarction, and intracerebral haemorrhage, as well as total mortality". 

There's still a whole lot we don't know about how different types of flavonoids in the things we eat and drink are affecting our health, but research is showing that a cup of tea or two per week week is a pretty good bet if you want to do something healthy for your heart.