Health Professional Newsletter
Welcome to the fifth newsletter from the United Kingdom Tea Council. This service will keep you up to date with current Tea4Health activities and events and inform you of the latest published research. We'll keep you updated on a quarterly basis with news and views from across the tea industry.
Research Update
Black tea reduces the risk of ovarian cancer
Tea and its constituent compounds have been hypothesised to influence cancer risk. The effect of black tea on a specific type of cancer, ovarian cancer, was recently investigated among a group of American women.
This hospital-based, case-control study, included 414 women with primary epithelial ovarian, fallopian or peritoneal cancer who were treated at the Roswell Park Cancer Institute (RPCI) in Buffalo, New York, between 1982 and 1998 and 868 controls who had received medical services at RPCI for non-neoplastic conditions. Diet was assessed using a 44 item food frequency questionnaire that recorded usual intake during ‘the past few years before illness’. A separate section assessed beverage intake including usual servings of black tea, decaffeinated tea, regular coffee and decaffeinated coffee.
A linear decline in ovarian cancer risk was observed with increasing black tea consumption. Compared to women who did not drink black tea, women with a usual consumption of at least 2 cups a day experienced a 30% decline in ovarian cancer risk.
Although methodological issues of case-control studies need to be considered, the authors conclude by suggesting that the results from this study support a potential protective effect of tea consumption on ovarian cancer risk.
Baker J.A. et al 2007, Consumption of black tea or coffee and risk of ovarian cancer. Int J Gynecol Cancer 17;50-54
Can black tea prevent lung damage caused by smoking?
It is well known that cigarette smoking is a major cause of lung damage with one of the proposed mechanisms involving the effect of cigarette smoke on oxidative stress. Oxidative stress results when an abundance of unstable molecules called free radicals, or oxidants, roam around the body. Smoking loads the body with millions of free radicals every time smoke is inhaled. In an attempt to stabilise themselves these free radicals attack healthy cells. This can result in cell death (apoptosis) and if this happens in the lung, subsequent lung injury.
Antioxidants can help mop up these free radicals and neutralise them, so potentially preventing cell damage from occurring. As black tea has antioxidant properties the effect of black tea on cigarette smoke induced apoptosis and lung injury was examined in a guinea pig model.
Guinea pigs were exposed to cigarette smoke from 5 cigarettes a day for seven days and given either water or black tea to drink. This exposure to cigarette smoking resulted in lung damage initiated by oxidative stress, which then resulted in inflammation, apoptosis and lung damage. All these events were prevented in the guinea pigs that were given black tea to drink as opposed to water.
Although it appears black tea can prevent smoke induced lung damage in guinea pigs, clinical studies investigating any potential benefits in humans is required.
Banerjee S, et al 2007, Black tea prevents cigarette smoke-induced apoptosis and lung damage. J Inflamm. Feb 14;4:3
Tea does not affect the iron status of healthy people
Iron has several vital functions in the body, its major role being as an Oxygen carrier in blood haemaglobin and muscle myoglobin. Deficiency in dietary iron can ultimately result in anaemia. Dietary sources of iron include both haem (meat, liver, offal, etc) and non-haem sources (cereals, vegetables, pulses, dried fruit, etc). The absorption of non-haem iron is less efficient than haem iron and is affected by a number of dietary factors that can either inhibit or enhance its absorption. Phenolic compounds found in foods such as tea, have been suggested to reduce the absorption of non-haem iron and as a result tea is often advised against in preventing anaemia.
To determine whether tea does affect the iron status of a healthy adult population, researchers in France examined 954 men (aged 52-68 years) and 1639 women (aged 42-68 years) who were participants of the SU.VI. MAX study. To establish tea intake these subjects completed a detailed questionnaire on tea consumption. To ascertain iron status serum ferritin was measured from a venous blood sample. Iron depletion was defined as a serum ferritin concentration of <16mug/l. Other dietary enhancing or inhibiting factors were also examined using three 1 day food diaries.
Results from this study found that mean serum ferritin concentration was not related to black, green and herbal tea consumption in men, pre or post-menopausal women. Furthermore it was not related to the strength of tea, the infusion time or the time of tea drinking.
The authors concluded by suggesting that normal, apparently healthy adults are not at risk of iron depletion as a result of any type of tea drinking.
Advice on tea drinking may need to be tailored to individuals who are at risk of developing anaemia or who have a poor iron status.
Mennen L et al, 2007, Consumption of black, green and herbal tea and iron status in French adults. Eur J Clin Nutr Feb 7; (Epub ahead of print)
The truth about caffeine and hydration during exercise
A popular belief still held is that certain substances, such as caffeine, have a detrimental effect on hydration. As a result recommendations for many years have advised active individuals to avoid caffeinated beverages when exercising, with little supporting scientific proof. A recent review has examined the evidence relating to this topic and concluded that moderate intakes of caffeine does not compromise hydration status either at rest or during exercise.
The authors of this review investigated studies that considered the acute effects of caffeine ingestion and concluded that intakes of <300mg (equivalent to 6 cups of tea in one sitting) does not promote dehydration at rest or during exercise. Furthermore they suggested that the long term ingestion of low to high doses of caffeine does not compromise hydration status and thermoregulation at rest or during exercise. Varying one’s level of caffeine ingestion (either increasing or decreasing) also does not appear to change hydration status.
Finally the authors conclude by recommending that hydration advice given in clinical practice should be dictated by evidence in the literature rather than perpetuating unproven myths.
Ganio MS, et al, 2007, Evidence-based approach to lingering hydration questions. Clin Sports Med Jan;26(1):1-16
Other News
Further support for tea’s positive effect on hydration
The British Dietetic Association (BDA) has recently posted an informational piece for the media on their website entitled ‘The Facts About Hydration’. This topical feature, which aims to provide journalists with accurate and factual information, discusses the importance of fluid in the body, its regulation, as well as the effects and signs of dehydration. The BDA recommend that 1.5-2.5 litres of fluid will be sufficient for most people, although additional fluids will be required for the more active and those living in hot environments. Sources of fluid are suggested, including beverages such as tea. They conclude by saying, ‘Caffeine is a diuretic (including loss of water in the body) in high concentrations, however research shows that diuretic effects are not significant in the styles of tea and coffee typically consumed in the UK, and so such caffeinated beverages also support hydration’.
Further information can be found at www.bda.uk.com
The effect of adding milk to tea – what’s the story?
Recently tea hit the headlines following a study1 that suggested adding milk to the nation’s favourite cuppa blocks the effectiveness of compounds found in tea that maybe beneficial for heart health. While the results of this study are interesting, they need to be put into perspective; there is now a strong body of research to suggest that adding milk to tea does not block health gains and may in fact enhance it.
This study, published in the European Heart Journal, was conducted among a very small sample (n=16) of post-menopausal women in Germany. The researchers compared the endothelial function in the brachial artery of these women, after drinking black tea with no milk, black tea with milk, or hot water. They found that while tea increased the artery's ability to relax and expand to accommodate increased blood flow compared to water, this effect was blocked when milk was added to the beverage.
It was suggested that this was as a result of compounds called catechins (types of flavonoids) in tea, which helped the blood vessels dilate by producing a chemical called nitric oxide. The proteins found in milk stopped this effect by reducing the concentration of catechins in the tea.
Despite this observation, there are in fact over 200 bioactive compounds that have been found in tea. These may bring about health benefits in a variety of ways unrelated to vasodilation. Just because milk may effect vasodilation does not mean that all other beneficial effects will be negated. In fact a number of other studies have demonstrated that milk does not affect the bioactivity of tea flavonoids.2-4
Tea with or without milk is important for hydration as well as being a source of a number of nutrients including fluoride. Furthermore, adding milk to tea can boost the intake of essential vitamins and minerals not normally found in tea. For example just four cups of tea can provide upto 21% of the recommended daily intake for calcium.
Whether you take yours with or without milk, there are still numerous benefits to continue to enjoy drinking your favourite cuppa.
1. Lorenz M, et al 2007, Addition of milk prevents vascular protective effects of tea. Eur Heart J. Jan;28(2):219-23. Epub 2007 Jan 9
2. Reddy et al, 2005, Addition of milk does not alter the antioxidant activity of black tea. Ann Nutr Metab. May-Jun;49(3):189-95
3. Leenan et al, 2001, A single dose of tea with or without milk increases plasma antioxidant activity in humans. European Journal of Clinical Nutrition. Jan;54(1):87-92
4. Hollman et all, 2001, The addition of milk to tea does not affect the absorption of flavonoids from tea in man. Free Radical Research. Mar;34(3):297-300
Visit us at the Royal College of Nursing (RCN) Congress to discover more about the health benefits of tea
The United Kingdom Tea Council (UKTC) will be exhibiting at the RCN Congress this year (16th-18th April ’07, Harrogate International Centre) where a Nutritionist will be on hand to answer any questions relating to tea and health.
Please visit www.rcn.org.uk for more information
