Black teas contain more complex flavonoids than green teas, specifically thearubigins and theaflavins. These polyphenols can act as antioxidants to protect low density lipoproteins from oxidation and inhibit atherogenesis (the build-up of plaque in the arteries) (1), which is involved in the development of cardiovascular disease (2). Other possible functions include reducing inflammation in atherosclerosis, reducing thrombosis, promoting normal endothelial (arterial wall) function, and blocking expression of cellular adhesion molecules, which cause blood clots to form.
Tea also has many other benefits including reducing your risk of Alzheimer's, various cancers and many other forms of chronic illness, but I will consider only cardiovascular benefits in this article.
In particular, observational studies suggest that a high intake of both green and black tea is related to a reduction in cardiovascular disease (CVD) risk, including both heart attack and stroke (3,4).
Studying the flavonoid intake of 805 men aged 65 to 84 and followed for five years, researchers reported that flavonoid intake was significantly inversely associated with mortality from coronary heart disease and showed an inverse relation with incidence of myocardial infarction (heart attack). There was a 42% risk reduction of coronary heart disease mortality in the highest versus the lowest measured flavonoid intake. The major sources of flavonoid intake were tea (61%), onions (13%) and apples (10%), and intakes of tea, onions and apples were inversely related to coronary heart disease mortality (5). In an Australian study of 1,063 women over 75 years of age, those with the highest consumption of flavonols had a lower risk of atherosclerotic vascular disease death (6). This study also found an increased consumption of flavonols was independently associated with a lower risk of atherosclerotic vascular disease mortality.
Three Cups a Day
In a longitudinal analysis on 4,807 men and women aged 55 years and older, the risk of heart attack was 57% lower in tea drinkers with a daily intake of more than 375 millilitres compared to non-tea drinkers. In a prospective cohort study of 37,514 participants consuming three to six cups of tea (mainly black tea) a day was associated with a reduction in the risk of chronic heart disease mortality (7).
In an analysis of 10 cohort studies and seven case-control studies (8), researchers found an 11% reduction in the risk of heart attack when consuming three or more cups of tea a day. A study of 2,613 men and 3,984 women, aged about 73, found women who drank tea reduced levels of plaque build-up in their arteries thereby reducing risk for heart disease and stroke. The study found carotid plaques were evident in 45% of non-tea drinking women, in 42.5% of women drinking one to two cups of tea daily and in only 33.7% of those drinking three or more cups a day.
Numerous clinical trials as well as large population studies have found that regular tea drinkers are as much as 44% less likely to suffer a heart attack than the general population, and those who have had heart attacks are more likely to recover. Researchers found that tea appears to repair blood vessel damage in people who have coronary-artery disease.
Lower LDL cholesterol
Another study, in which everything subjects ate and drank was controlled, found that consistent tea drinking significantly lowered LDL cholesterol without decreasing HDL cholesterol. Black tea was found to produce statistically significant reductions in low-density lipoprotein (LDL) cholesterol and blood pressure (systolic blood pressure, SBP, and diastolic blood pressure, DBP) over six months. A randomised double-blind placebo-controlled study to investigate the benefits of taking black tea extract in 47 Japanese patients with borderline high cholesterol found that black tea extract significantly lowered patients' low-density lipoprotein (LDL) cholesterol and blood total cholesterol levels (9).
In a meta-analysis of nine studies involving 4,378 strokes among 194,965 individuals, researchers found that drinking three or more cups of green or black tea a day may reduce the risk of stroke by 21% and the more you drink, the greater the cuts in stroke risk. Researchers found a linear association with another three cups, reducing the risk by another 21%. It didn't matter if it was green or black tea. In a study of 552 elderly Dutch men followed for 15 years, the risk of stroke for those who drank more than 2.5 cups per day of black tea was only about a third (31%) that of men who drank less than 1.4 cups per day.
To explain some of the benefits of tea drinking on diabetes, a study of 16 healthy subjects drinking black tea was associated with a small but significant increase in insulin levels compared with the control and caffeine drinks at 90 minutes (10). It is probably the polyphenol content of the tea that is behind the effects, as these compounds could have an insulin-stimulating effect on pancreatic B-cells-cells responsible for insulin production.
While blood pressure is a significant risk factor for CVD, variation in blood pressure is also a risk factor. Black tea lowers the rate of blood pressure variation. In a randomised trial of 111 men and women with systolic blood pressure between 115 and 150 mm Hg, it was shown that black tea lowers the rate of blood pressure variation (11).
Despite the fact that milk binds with the flavonoids in tea, it does not appear to reduce the antioxidant benefits and although tea has relatively high levels of caffeine it does not appear to lead to dehydration. In support of this, my mother and many of her friends rarely ever drank water (not something I am advocating) but would have 10 cups of tea a day and she lived well and off medications until age 88.
What becomes clear from these studies alone is that simple tea as we consume it in Australia, the US, UK and New Zealand out performs any drug and has only positive side effects like cancer reduction. As a part of a healthy living-longer regime, my suggestion, as you will see in my next articles, is to drink lots of tea, any type but without sugar, and also make sure you drink lots of clean, mineralised alkaline water as well.
DISCLAIMER: Dr Peter Dingle is a researcher, educator and public health advocate. He has a PhD in the field of environmental toxicology and is not a medical doctor.
Wall et al. 1997
Hodgson et al. 1999
Rimm et al. 1993
HYPERLINK "http://journals.cambridge.org/action/displayJournal?jid=BJN" British Journal of Nutrition 2013, DOI: HYPERLINK "http://dx.doi.org/10.1017/S0007114513000780" "_blank" 10.1017/S0007114513000780
de Koning Gans 2010
Bryans et al. 2007
Am J Clin Nutr May 2013 vol. 97 no. 5 943-950
Dr Peter Dingle (PhD) has spent the past 30 years as a researcher, educator, author and advocate for a common sense approach to health and wellbeing. He has a PhD in the field of environmental toxicology and is not a medical doctor. He is Australia’s leading motivational health speaker and has 14 books in publication.