Black tea superpower: Researchers find flavonoids in leafy beverage may reduce heart disease

24 Nov 2022 --- A study conducted by Edith Cowan University (ECU) has discovered that the flavonoids in black tea and apples, among others, can contribute significantly to reducing the build-up of abdominal aortic calcification (AAC) and facilitate improved heart health later in life.

AAC is the calcification of the abdominal aorta, the largest artery in the body, which supplies oxygenated blood from the heart to the abdominal organs and lower limbs. 

“AAC is a major predictor of vascular disease events and this study shows intake of flavonoids, that could protect against AAC, is easily achievable in most people’s diets,” says Ben Parmenter, study lead and ECU Nutrition and Health Innovation Research Institute researcher.

Dietary sources with high levels of flavonoids are most effective in this regard. The study flags that many different flavonoids, such as flavan-3-ols and flavonols, have a relationship with AAC.

Study participants with a higher intake of total flavonoids, flavan-3-ols and flavonols were 36-39% less likely to have extensive AAC. Black tea was the study cohort’s main source of total flavonoids and was associated with significantly lower odds of extensive AAC.

Cardiovascular health and dementia predictor
The extent of AAC is a major predictor of vascular disease events. “We have previously found regular apple intake, a major source of dietary flavonoids, associates with lower AAC,” the researchers note in the study “Higher Habitual Dietary Flavonoid Intake Associates With Less Extensive Abdominal Aortic Calcification in a Cohort of Older Women,” published in Arteriosclerosis Thrombosis and Vascular Biology.

“Whether total dietary flavonoid intake impacts AAC remains unknown. Here, we extend our observations to habitual intakes of total flavonoids, flavonoid subclasses and specific flavonoid-containing foods, with the odds of extensive AAC,” they note.

Compared with respondents who didn’t drink tea, participants who had two to six cups per day had a 16-42% less chance of having extensive AAC. However, other dietary sources of flavonoids, such as fruit juice, red wine and chocolate, did not show a significant beneficial association with AAC.Flavonoids are naturally occurring substances in many common foods and beverages, such as black and green tea, apples, nuts, citrus fruit, and berries.

“In most populations, a small group of foods and beverages uniquely high in flavonoids contribute the bulk of total dietary flavonoid intake. The main contributors are usually black or green tea, blueberries, strawberries, oranges, red wine, apples, raisins/grapes and dark chocolate,” Parmenter explains.

Research conducted by the American Heart Association showed that flavonoid-rich foods such as berries, apples, pears and wine might positively affect blood pressure levels. The association was explained by the characteristics of the gut.

The experiment
The researchers conducted cross-sectional analyses on 881 elderly women (median age of 80), which found they were far less likely to have an extensive build-up of abdominal aortic calcification (AAC) if they consumed a high level of flavonoids in their diet.

Flavonoid intake was calculated from food-frequency questionnaires. Calcifications of the abdominal aorta were assessed on lateral lumbar spine images and categorized as less extensive or extensive. Logistic regression was used to investigate associations.

They concluded that greater habitual dietary flavonoid intake in older women is associated with less extensive AAC, a predictor of cardiovascular risks such as heart attack and stroke. It has also been found to be a reliable predictor for late-life dementia.

Alternative sources of flavonoids
While black tea was the main source of flavonoids in the study, the researchers claim people can also draw these health benefits from other flavonoid sources.

“Out of the women who don’t drink black tea, higher total non-tea flavonoid intake also appears to protect against extensive calcification of the arteries. This implies flavonoids from sources other than black tea may be protective against AAC when tea is not consumed,” Parmenter outlines.

“In other populations or groups of people, such as young men or people from other countries, black tea might not be the main source of flavonoids,” he says.

Edited by Inga de Jong