Tea is the number one drink for health. It’s also our absolute favourite according to a recent BBC programme1. Nothing we eat or drink in Britain comes close. We drink 165 million cups every day. That’s 15 billion litres of tea every year. The good news is that tea is very good for us. The following e-news from the Tea Advisory Panel reviews some of the latest research that continues to highlight the many health benefits of a good cuppa.
Black tea vs. water for hydration
It is a common belief that caffeinated drinks, such as tea, may adversely affect body hydration levels. We are sometimes given advice to limit consumption of caffeinated drinks, or drink water alongside them. A randomised cross-over trial in adults has investigated whether or not this claim is true in relation to tea drinking.
In a cross-over trial2, 21 healthy men were randomised to drink either four or six mugs of regular ‘black’ tea (containing 168mg or 252mg caffeine), or similar amounts of boiled water over one day. The tea was made each time in a standardised way. There was a five day washout period between the tea and water conditions. All men took part in all test conditions and, during these, blood and urine samples were taken at regular intervals to monitor hydration status. It was important to have measures of both blood and urine as this is the gold standard method for assessing hydration.
The results revealed that the various indicators of hydration status, e.g. blood and urine osmolality, total urine volume, blood urea, were no different after drinking tea or water. This suggests that drinking up to 6 mugs of tea daily has similar hydrating properties to drinking plain water. Average tea intakes in the UK are currently 2-3 servings per day which are well within the limits tested in this study. These findings therefore suggest that drinking up to six cups of tea per day, has similar hydrating properties to water. The average intake of tea in the UK is two to three cups per day, so most tea drinkers are within the six cups per day range.
Dr Ruxton’s research is supported by other studies. A two-day intervention, carried out at altitude, reported no differences in 24-hour urine output or hydration measures when participants drank tea or water3. In a randomised, controlled crossover trial in18 sedentary adults, the effect of water, cola and coffee on hydration was compared over a 24-hour period. No significant differences were found between the different drinks for any markers of hydration4. Caffeine intakes in this study ranged from 114-253mg. Another study found that caffeinated beverages appear to have no diuretic action. This was suggested by the authors to be due to the modest amounts of caffeine found in tea and coffee being too low to cause dehydration, and the possibility that consumers of caffeinated beverages develop tolerance to caffeine over time.5
As a result of the growing bank of research demonstrating that tea is just as hydrating as water, the Tea Advisory Panel is calling for public health guidelines to be changed to reflect the latest research findings, so that tea is recognised for its hydrating properties. The Tea Advisory Panel notes: “Wrong advice that identifies tea as dehydrating could be misleading and serve to drive consumption towards less healthy drinks. Given the findings of the recent trial data that consumption of tea at either four or six cups had no adverse effects on hydration and bearing in mind that tea is one of the top drinks to meet daily water needs, it could be argued that public health advise relating to caffeinated drinks should be revised.”
A recent paper by nutritionists Dr Carrie Ruxton and Dr Pamela Mason found that drinking three or more cups of black tea each day protects against heart disease and that two or more cups a day may protect against type 2 diabetes.
These protective effects are believed to be due to the presence of flavonoids in black tea. Black tea is the number one source of these extremely powerful bioactive compounds in the British diet. Studies have shown that flavonoids have antioxidant and anti-inflammatory properties and reduce the proliferation or growth of body cells.7,8 The main examples in black tea are the theaflavins, thearubigins and catechins.
Commenting on the many health benefits that tea possesses, Dr Tim Bond from the Tea Advisory Panel notes: “Black tea flavonoids are thought to be the compounds responsible for the protective effects of black tea on health. Chronic conditions such as heart disease, stroke and diabetes are associated with inflammatory processes and the presence of excessive pro-oxidant free radicals in the body. The proven antioxidant and anti-inflammatory effects of black tea flavonoids may therefore be responsible for the positive health effects of black tea described in Ruxton and Mason’s paper.
“Other recent studies continue to confirm the health benefits of black tea, particularly for cardiovascular health. A 12-week study in 87 volunteers found that drinking 3 cups of tea a day produced a significant improvement in various CVD risk factors. The ratio of LDL/HDL cholesterol fell while the levels of both blood triglycerides (a type of blood fat) and fasting glucose (blood sugar) also decreased. There was a significant rise in the antioxidant capacity of the blood and the level of the beneficial HDL cholesterol also increased9. A meta-analysis10 found that tea consumption can improve endothelial function in the blood vessels, helping to improve blood flow, while a randomised controlled trial in 95 men and women showed that consumption of three cups of black tea each day significantly reduced blood pressure.11”
Getting the most health benefit from black tea may depend on the brewing time according to a demonstration by Dr Tim Bond on the BBC programme. Black tea was brewed for between 30 seconds and 7 minutes and the antioxidant potential measured in each case. Antioxidant potential in the 7-minute brew was three times as high as in the 30-second brew.
The average brew time in the UK is about 40 seconds, said Dr Bond and leaving the tea bag for just 3 minutes could double the antioxidant potential in a cup of tea compared to the average brew.
In summary, Dr Carrie Ruxton from TAP notes: “There is far more to the nation’s favourite drink than we realise. With its antioxidant flavonoids, black tea packs a powerful punch with many health benefits particularly for the heart. And recent studies show that the flavonoids work their magic whether or not we choose to add milk. All in all, drinking four or more cups of black tea each day is quite simply very good for us as well as keeping us as hydrated as water!”
1 Britain’s Favourite Supermarket Foods. http://www.bbc.co.uk/iplayer/episode/b01c89y8/Britains_Favourite_Supermarket_Foods/
2 For more information see: Ruxton CHS & Hart VA (2011) British Journal of Nutrition Vol.66: pg 588-95.
3 Scott D Rycroft JA, Aspen J, Chapman C, Brown B (2004). The effect of drinking tea at high altitude on hydration status and mood. European Journal of Applied Physiology. 91, 4, 493-498.
4 Grandjean AC, Reimers KJ, Bannick KE, Haven MC (2000). The effect of caffeinated, non-caffeinated, caloric and non-caloric beverages on hydration. Journal of the American College of Nutrition. 19, 5, 591-600.
5 Maughan RJ, Griffin J (2003). Caffeine ingestion and fluid balance: a review. Journal of Human Nutrition and Dietetics. 16, 6, 411-420.
6 Ruxton, CHS, Mason P. Is black tea consumption associated with a lower risk of cardiovascular disease and type 2 diabetes? Nutrition Bulletin 2012. 37, 4–15
7 Ruxton CHS (2009) The health effects of black tea flavonoids. Nutrition and Food Science 39: 283–94.
8 Mulvihill EE & Huff MW (2010) Antiatherogenic properties of flavonoids: implications for cardiovascular health. Canadian Journal of Cardiology 26 (Suppl. A): 17A–21A.
9 Bahoran T, Luximon-Ramma A, Nergheen Bhujun VS et al. The effect of black tea on risk factors of cardiovascular disease in a normal population. Prev Med 2011. doi: 10.1016/j.ypmed.2011.12.009
10 Ras RT, Zock PL, Draijer R. Tea consumption enhances endothelial dependent vasodilation; a meta-analysis. PLoS One. 2011;6(3):e16974.
11 Hodgson, J, Puddey, I, Woodman R et al. Effects of Black Tea on Blood Pressure: A Randomized Controlled Trial. Arch Intern Med 2012, 172 (2). Jan 23.
The Tea Advisory Panel: The Tea Advisory Panel is supported by an unrestricted educational grant from the UK TEA COUNCIL, the trade association for the UK tea industry. The Panel has been created to provide media with impartial information regarding the health benefits of tea. Panel members include nutritionists; dieticians and doctors. For further information please call 0207 7052 8989.
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