Tea is one of the healthiest drinks in the world when it comes to your heart, circulation and blood pressure. The health benefits of drinking tea were well known in China, where it was considered a medicinal beverage. The name of one brand, TyPhoo was even derived from the Chinese term, daifu, which means doctor.
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Green versus black tea
Green, black, white and oolong tea are all made from the young leaves and buds of the shrub, Camellia sinensis, of which two main strains are used: the small-leaved China tea plant, Camelia sinensis, and the large-leaved Assam tea plant, Camelia sinensis assamica.
Green tea is made by steaming and drying fresh tea leaves immediately after harvesting. Matcha tea is made by grinding dried green leaves to a powder, so you consume the whole leaf rather than just an infusion.
Black tea is made from the same leaves as green tea, but they are crushed and fermented so they oxidise before drying. This releases natural enzymes which produce the characteristic red-brown colour and reduced levels of astringency.
Of the tea consumed worldwide, 20% is taken as green tea, mainly in Asia, while 80% is drunk as black tea, mainly in the West.
Tea and blood pressure
The blood pressure benefits of tea come from the high levels of flavonoid antioxidants present in the leaves, which improve blood flow and blood vessel elasticity.
In green tea leaves, 30% of the antioxidants present are catechins, such as epigallocatechin-3-gallate (EGCG). In black tea, the level of catechins is reduced to around 10% as they are converted into different classes of antioxidant (eg theaflavins and thearubigins) during fermentation.
It was originally thought that adding milk to black tea might bind the antioxidants and reduce their effectiveness, but studies have found no difference in the level of antioxidants absorbed into the circulation when drinking tea with or without milk.
While tea is a natural source of caffeine, which might be expected to increase blood pressure (at least temporarily) this effect is neutralised by the presence of a unique tea amino acid called L-theanine. L-theanine supports the alerting effect of caffeine but is relaxing and so that drinking tea has a more refreshing and relaxing effect than drinking coffee, which is less likely to cause over-stimulation or to interfere with sleep, and which also has beneficial effects on blood pressure. Matcha tea contains particularly high amounts of L-theanine as it is prepared from the whole powdered leaf rather than an infusion.
Both black and green tea appear to be equally effective for lowering blood pressure.
The results from thirteen trials, involving 1,367 people, found that drinking green tea lowered blood pressure by 1.98/1.92 mmHg compared with not drinking tea. Similarly, the results from 11 studies show that drinking 4 to 5 cups of black tea per day is associated with a blood pressure that is 1/8/1.3 mmHg lower than for non-tea drinkers, after accounting for other factors.
Overall, the regular consumption of green or black tea, for at least 2 months, can lower blood pressure by an average of 2.36/1.77 mmHg in people with prehypertension or hypertension.
Tea and heart disease
These blood pressure reductions may not seem like much, but they are enough to significantly reduce your long-term risk of a heart attack or stroke. And, as well as lowering blood pressure, tea polyphenols have beneficial effects on blood lipids, reduce blood stickiness and increase the elasticity of blood vessel walls. Drinking tea can even slow the progression of calcification in coronary artery walls.
Studies involving over 856,200 people suggest that increasing your tea consumption by 3 cups per day has the potential to reduce your risk of a heart attack by 27% and your risk of a stroke by 18%. In fact, tea drinking was associated with a 24% lower risk of dying from any medical cause during the duration of the studies.
Green tea extracts
For those who don’t like drinking tea, green tea extracts are available. A recent study compared the effects on blood pressure of taking either green tea extract capsules (three times 500 mg, each containing 260 mg polyphenols) or placebo, for 4 weeks. Twenty woman took both treatments, over two separate occasions, and their systolic blood pressure (upper figure) was significantly lower after 4 weeks of taking the green tea extract (3.61mmHg lower during daytime and 3.94 mmHg lower during night-time) compared with placebo.
If you have high blood pressure, aim to drink four cups of green or black tea daily, or consider taking green tea extracts.
For more health benefits of drinking tea, visit Nutritional Medicine.
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