Tea & Cancer
Cancer is a complex disease that occurs when genetic damage triggers uncontrolled cell growth. Two-thirds of all cancers that occur are linked to tobacco use and dietary factors such as alcohol consumption and high-fat foods. Diet also is important in lowering cancer risk. Observational studies suggest that increased consumption of plant foods such as fruits, vegetables and tea are associated with a lower risk for cancer.
Breast Cancer:
Green tea may favorably alter estradiol and sex hormone-binding globulin levels associated with the risk of breast cancer.
Colorectal Cancer:
Green tea appears to have a protective effect on colorectal cancers in several studies conducted in Japan and China.
Bladder Cancer:
A study of 4,000 Americans indicated intake of more than five cups of tea a day was associated with a 30% reduction in risk of bladder cancer.
Prostate Cancer:
A case-control study of 1,254 Canadians found a 30% reduction in the risk of prostate cancer with tea intakes of at least 16 ounces per day.
Skin Cancer:
Several studies involving both laboratory animals and humans show tea polyphenols effective against chemical and ultraviolet-light induced skin cancer.
Bone Health:
A study of 1,256 British women, 65-76 years of age, found that those who drank tea had greater bone mineral density than those who did not drink tea.
Tea, Heart Disease and Stroke:
Coronary heart disease affects 57 million Americans and kills nearly one million men and women each year. In light of such high heart disease prevalence and mortality rates, even a small reduction in risk for coronary heart disease, resulting from improved diet and lifestyle, could have a significant impact on public health.
Some recent animal and human studies suggest that tea antioxidants may help reduce the risk of heart disease and stroke in two ways: by maintaining the health of the body’s circulatory system of arteries and veins, and by reducing the risk of blood clots.
A number of recent population studies conducted in the United States and Europe have found that black tea consumption is associated with a reduced risk of heart disease and stroke. In one of studies, more than 800 elderly Dutch men who consumed 3.4 cups of tea per day decreased their risk of death from coronary heart disease by 58%, compared to those who consumed lesser amounts of flavonoid-rich foods. In another analysis of the same group of men, those who drank 4.7 or more cups of black tea per day had a 69% lower risk of stroke compared to those who consume, on average, less than 2½ cups of black tea per day.
Antioxidants in Tea:
Like fruits and vegetables, hot and iced tea contains natural compounds called antioxidants. Research suggests that dietary antioxidants can neutralize free radicals, helping maintain healthy cells and tissues in the body. Free radicals, occurring in the environment and naturally produced by the body, can cause oxidative damage to cells, and thus contribute to chronic conditions such as heart disease or cancer.
USDA researchers, using a test tube measure called ORAC, found that an 8-ounce serving of black or green tea is more effective in neutralizing free radicals than individual servings of more than 33 commonly consumed fruits and vegetables, including apples, grapes, kiwi, grapefruit, garlic, broccoli, carrots and Brussels sprouts.
According to other researchers, tea flavonoids are more powerful antioxidants than vitamins C, E and beta-carotene against a number of free radicals (in test tube studies).
Preliminary data from human studies suggests that drinking tea may reduce oxidative damage to cells and tissues. A study conducted in both China and the U.S. found that drinking green tea reduces levels of oxidative damage in both smokers and nonsmokers. Other studies from Asia also found lower levels of oxidative damage in people consuming tea.
Tea and Caffeine
Black tea has about half the caffeine as the same serving of coffee.
Extensive research shows that a moderate caffeine intake of about 300-mg per day (eight cups of brewed hot or iced tea) is not a health risk.
There is no link between moderate caffeine consumption and risk of cancer, cardiovascular disease or osteoporosis.
The U.S. FDA has stated that caffeine does not adversely affect reproduction in humans in terms of fertility, pre-term delivery, birth defects, or low birth weight. The USDA does continue to advise pregnant women to consume caffeine in moderation.
More Facts and Finding on Benefits
- Some studies suggest drinking 5 servings per day of black tea with a moderately low-fat diet reduces total and LDL (bad) cholesterol significantly and can therefore decrease the risk of Coronary Artery Disease. A USDA study showed that subjects who drank 5 cups of black tea per day for 3 weeks lowered their LDL cholesterol by 7%.
- Antioxidants (polyphenols and flavanoids) found in tea inhibit cell damage caused by free radicals (unstable molecules that occur naturally in the body). Free radical action has been implicated in certain disease states such as cancer, heart disease, stroke, rheumatoid arthritis and Alzheimer’s disease.
- Black and green teas contain similar amounts of dietary flavanoids (substances with antioxidant activity thought to protect against heart disease, stroke and cancer); however, the flavanoids differ in chemical structure. Both types of tea provide comparable health benefits.
- A 6 oz. cup of tea contains 50 mg. caffeine – that’s 1/2 less than an equal amount of coffee. Caffeine intake up to 300 mg. per day (6 cups of tea) is considered moderate and causes no undesirable effects for most adults.
- Drinking tea was associated with lower levels of dental cavities in a cross-sectional study of secondary school children in England. Tea may have a beneficial impact on cavities because of its natural fluoride. In addition, extracts of green tea inhibit oral bacteria.
- Oolong tea is a traditional Chinese tea long believed to be beneficial to health and possibly able to reduce body fat. A study in Japanese females found that those who drank Oolong tea had a slightly increased energy metabolism as compared to those drinking other beverages.
- Research suggests adding sugars, sweeteners, lemon or milk will not affect the antioxidant activity of your tea.
- EGCG, a substance in green tea, may decrease the risk of cancer. One study showed that green tea inhibits vascularization (blood vessel formation) in human breast cancer cells, while another study suggest that EGCG inhibits DNA replication in leukemia cells, resulting in the death of these cancer cells.
- Dietary flavanoids, of which tea is an excellent source, may protect against heart disease. Conclusions from an analysis of all studies investigating the relationship between tea and heart disease suggest drinking 3 cups of tea per day may reduce the risk of heart attack by 11%.
- Black tea’s weapon against colon cancer may be a compound called theaflavin 3-monogallate (TF-2). Lab experiments show colon cancer cells commit suicide in the presence of TF-2 while normal cells remain unharmed. TF-2 is also an inhibitor of a gene (COX 2) known to trigger inflammation (a step in the incidence of cancer).
- Research at the University of Kansas measured the antioxidant content of green tea and found it to be 100 times more effective than Vitamin C and 25 times better than Vitamin E in protecting cells from free radical damage. Still, eat your fruits and vegetables though, as tea consumption will not counteract the effects of a poor diet.
- Preliminary findings indicate that tea boosts the body’s defenses against infection. Specifically, a study showed that immune system blood cells from tea drinkers responded to germs 5 times faster than did the cells of coffee drinkers.
- There is growing evidence that drinking tea may benefit oral health. Tea is an excellent source of Fluoride, a substance that strengthens tooth enamel, making teeth more resistant to cavities. Furthermore, other components in tea (flavanoids and tannins) seem to have anti-plaque, anti-bacterial effects, protecting the teeth from cavities.
- A study suggests that habitual tea consumption (especially greater than 10 years) has significant beneficial effects on bone mineral density of the total body, spine and hip regions in adults.
- Various studies suggest that green tea may protect against skin cancers as topical treatment and drinking green tea may protect the skin from UV-ray damage.
- There is increasing evidence that the inclusion of tea in a balanced diet rich in fruits, vegetables and whole grains and low in fat can enhance heath. Other lifestyle factors (i.e. exercise, maintaining healthy body weight, not smoking, moderate use of alcohol) must of course be considered for optimal health. Consult your doctor if you have questions regarding a medical condition and tea consumption. Overall, tea is receiving the thumbs up as a healthy beverage, so drink to your health!
Above Findings from the Third International Scientific Symposium on Tea & Human Health, held September 23, 2002 at the United States Department of Agriculture in Washington , D.C.
