A good cup of tea can provide a comforting break from our hectic lives and has been enjoyed by people all over the world for thousands of years. Tea drinking first began in China and the love of tea has not abated since. In fact, according to the UN Food and Agriculture Organization, tea is the most popular beverage in the world. Only in recent decades have we discovered just how powerful this drink can be for our health.
In this discussion “tea” means the hot drink made from the leaves of the evergreen tea plant, camellia sinensis, indigenous to China and India. Herbal teas (peppermint, chamomile and others) are very healthful in their own right but originate from completely different plants.
The camellia sinensis plant yields four types of tea – black, green, white and oolong. The end product is dictated by how much the tea leaf is allowed to oxidize after its harvest and during its processing (46). Oxidation occurs naturally when chemicals in the leaves are broken down by enzymes. The oxidation process can be stopped by heating which inactivates the enzymes.
White tea is made from young leaves and buds and undergoes only minimal oxidation before it is dried. White tea retains all its natural antioxidants but does not develop much flavour or colour.
Green tea is made from unwilted leaves that have not oxidized. This brings out a fresher flavour and allows caffeine to develop although some antioxidants are lost.
Oolong tea is allowed to wilt and partially ferment. It is then shaken to release additional flavour. Oolong tea has more caffeine and fewer antioxidants than green tea.
Black tea is fully oxidized. The leaves are allowed to wilt and then they are bruised and rolled, causing the leaves to turn black and to form tannins and higher amounts of caffeine. Black tea possesses the most robust flavour and the least antioxidants at a level of only 3% to 10% by weight.
Green tea seems to possess the most numerous health benefits among tea types. It contains about 40% by weight of antioxidants in the form of polyphenols, most of these being epigallocatechin-3-gallate (EGCG). Others are epicatechin (EC), epicatechin-3-gallate (ECG) and epigallocatechin (EGC). These phytonutrients have very powerful benefits for a wide range of our modern health concerns.
Green tea is good for cardiovascular health
Studies have found that drinking tea can protect against cardiovascular disease and may reduce the risk of heart attacks (31). The endothelium, the single cell layer that lines our blood vessels, is critical to good health. Unfortunately endothelial cells live for only about thirty years. In the Western world their replacements tend to be inferior leading to progressive diminishing of endothelial function starting around the age of 40 to 50. This decline however is not inevitable. For example, it does not occur in the Chinese population. It is theorized that the copious amounts of green tea commonly consumed in China provides benefits through the high levels of catechins (flavonoid phytonutrients) that are present in the tea leaves (9). Studies show that green tea consumption has an immediate beneficial effect on endothelial function (10). A randomized, double-blind, controlled, cross-over trial showed that even drinking black tea improved the function of the endothelium, decreasing arterial stiffness and improving flow mediated dilation, a measurement of the ability of an artery to dilate, by up to 10% (8).
Interestingly this cardiovascular benefit is completely prevented by adding milk to tea. In fact, in 2007, the European Society of Cardiology issued a press release warning that the effects of tea that are protective to the cardiovascular system completely disappear after the addition of milk (11). It appears that casein (milk protein) binds with phytonutrients and makes them unavailable to the body. The same effect occurs with soy protein (12).
Green tea can increase bone strength
Green tea fights osteoporosis by enhancing bone strength. There is mounting evidence from both animal studies and human epidemiological findings that green tea can restore the balance between osteoblasts (bone formers) and osteoclasts (bone destroyers) resulting in stronger bones (7). A six month randomized placebo-controlled trial on 150 postmenopausal women with low bone mass showed that 500 mg of green tea extract (the equivalent of 4 of 6 cups of green tea a day) resulted in improved markers for bone formation, reduced inflammation and increased muscle strength in participants (6).
Green tea is associated with reduced rates of Parkinson’s Disease
When a team of scientists monitored 29,335 Finnish men and women over the course of 12.9 years, they concluded that drinking tea was linked to an approximate 60% reduction in the risk of Parkinson’s Disease. This was true in both men and women, even after adjusting for other variables such as smoking, physical activity, age, and body mass index (21).
Green tea is linked to lower rates of Alzheimer’s Disease
Tea consumption has been associated with reduced rates of cognitive decline and Alzheimer’s Disease. Studies using functional magnetic resonance imaging (MRI) to investigate volunteers who were performing a working memory task found that brain activity was increased in the dorsolateral prefrontal cortex after consumption of green tea (29). Further studies of green tea consumption elucidated an increase in the connectivity between the frontal and parietal brain regions and improvement in cognitive performance (30). A 2010 study from the Proceedings of the National Academy of Sciences found that tea-derived EGCG can stop the accumulation of harmful beta-amyloid (a substance formed in the brain and implicated both in the death of neurons and Alzheimer’s Disease) by altering its tangled fibrils into more stable shapes that are not toxic to cells (34).
Green tea may reduce the ravages of arthritis
The polyphenols found in green tea, especially EGCG, have been found to be effective in reducing osteoarthritis and other inflammatory diseases (35). EGCG can regulate TAK1 kinase, a signaling protein that sends out pro-inflammatory cytokines and leads to the inflammation and tissue destruction of rheumatoid arthritis. This effect is showing promise as a new treatment possibility for arthritis (36).
Green tea may help to increase fat burning and decrease obesity
Studies of animal models show that green tea catechins reduce fat absorption and fat cell production as well as increase fat burning, all of which result in reduced body weight (32). Catechins from green tea increase the body’s ability to burn fat as a fuel, promoting improved muscle endurance in mice (1). Human studies have also shown reductions in body weight and waist circumference from green tea (33). Although a number of other published studies reiterate these positive effects in humans, the literature on this topic is inconclusive and more studies need to be performed to clarify the results (5).
Green tea fights prostate cancer
The effect of green tea on prostate cancer has been extensively studied. A 2006 randomized-controlled study on 60 men with precancerous prostate growth revealed an 80% reduction in the risk of those precancerous cells becoming full-blown prostate cancer. This benefit remained even a year after the subjects stopped drinking green tea (2,3). However, two subsequent trials, both uncontrolled, investigated the use of green tea extracts to reduce prostate-specific antigen levels in men with prostate cancer and found little benefit (27,38). In 2014 a new meta-analysis showed significant association between both black and green tea consumption and reduced prostate cancer risk (4). Ongoing trials should be able to shed more light on the potential of green tea to prevent prostate cancer.
Green tea contains antioxidants that may prevent cancer
The antioxidants in tea are full of promise for the prevention of a broad range of cancers, including cancers of the breast, colon, skin, lung, esophagus, stomach, small intestine, pancreas and liver. Many studies, both epidemiological and interventional trials, have shown a strong association between tea consumption and reduced risk of cancer (40,45). The antioxidants in green tea have substantial free-radical scavenging activity which may protect cells from DNA damage due to reactive oxygen molecules (39). Tea polyphenols have been shown to inhibit tumour cell growth both in the petri dish and in animal studies (40). Additionally tea catechins inhibit angiogenesis (growth of new blood vessels that are needed to support growth of a cancer) and the invasiveness of tumours (41). Tea polyphenols also protect against damage caused by ultraviolet B (UVB) radiation and can modulate immune system function (42) and they stimulate the action of detoxification enzymes that can protect against tumour development (43). EGCG has been shown to have the ability to kill cancer cells with no effect on normal cells (40). In spite of all these potential beneficial effects, more research needs to be done to determine the precise mechanism by which tea may prevent cancer and the extent to which tea could be used as a means to prevent and perhaps even treat malignancies (41,44,45).
Green tea can prevent infections including the flu
Catechins, the polyphenol phytonutrients in tea leaves, have been shown to have antimicrobial effects against a variety of organisms including viruses such as the human immunodeficiency virus (HIV), influenza A virus, herpes simplex virus, adenovirus and hepatitis B and C viruses (13,14). Studies also demonstrate the inhibitory effects of catechins on bacteria and fungi (14). A randomized, controlled study in Japan found that elderly residents of a nursing home who gargled with tea three times a day experienced a 7 to 8 fold lower incidence of influenza infection (15). A randomized, double-blinded, placebo-controlled trial of 200 healthcare workers showed a very significant 60% lower incidence of laboratory confirmed influenza in those consuming green tea catechins and theonine (16). And a study on schoolchildren revealed that those who drank from one to five cups of green tea a day experienced significantly less risk of influenza (17). Catechins appear to interfere with virus membranes and viral metabolic processes (18).
Green tea can fight other infections too
The effects of green tea on a wide variety of infections are a fairly recent discovery (13).
Fungal infections: Green tea has shown promise against athlete’s foot, ringworm and fungal
nail infections. A 2013 study showed significant improvement in symptoms of athlete’s foot with the use of a
green tea foot bath compared to a placebo solution (24).
Green tea reduces plaque and gingivitis in the mouth
A 2% green tea mouthwash is effective in killing the bacteria that cause plaque and gingivitis in
the mouth. A randomized controlled study illustrated an increase in the antibacterial power of
saliva after drinking green tea (25).
Green tea is effective against acne
Six weeks of treatment with a 2% green tea lotion can reduce the severity of acne pimples and
cut the total number of lesions in half (26).
Green tea shows promise as a treatment for bladder infections
Preliminary tests show the powerful inhibitory effect of green tea on E. coli, a common
cause of infections of the bladder and urinary tract (27,28).
Green tea can treat external genital warts
Ointments made of 10% to 15% green tea phytonutrients (Sinecatechins Ointment – Veregen) applied to external genital warts have been found to completely clear all warts in more than half of patients studied and offer higher effectiveness and lower recurrence rates than other available treatments (19). This astounding result led to the official incorporation of green tea ointment into the latest “Sexually Transmitted Diseases Treatment Guidelines” (20).
Green tea can treat fibroids in the uterus
Fibroids of the uterus have a detrimental effect on quality of life for the women burdened with them with no effective medicinal treatments currently available. In 2013 a double-blinded, placebo-controlled randomized clinical trial evaluated green tea extract (in the form of EGCG) in women with symptomatic uterine fibroids and found significant shrinkage in the size of the fibroids as well as greatly increased quality of life with no adverse effects. Those in the placebo group experienced an average of a 24% increase in the size of their fibroids (22)
Green tea contains caffeine….. which actually does have beneficial effects
Of course, unless it’s been decaffeinated, tea contains caffeine. Caffeine levels are higher in black and oolong tea compared to green or white tea. The health effects of caffeine are a controversial topic but a considerable body of evidence shows that the caffeine in tea may increase memory, help to ward off Alzheimer’s, protect against skin cancer and cataracts, prevent weight gain, help with asthma and even be advantageous for virility. Studies show that caffeine can enhance long-term memory even 24 hours after intake (23).
To sum it all up ….
Tea is a drink to be savoured without reservation.
A few pointers…
It is best to drink tea without milk.
For variety you can add a squeeze of lemon or a pinch of ginger.
If you drink iced tea, check labels on bottles. Many bottled teas contain large amount of sugar.
Iced tea also tends to have lower antioxidant levels than hot teas.
Most importantly, simply take some time out for yourself, brew up a cup of your favourite kind of tea, relax and enjoy.
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