Black tea is made from the dried leaves of Camellia sinensis, a shrub native to southeastern Asia. Green tea, black tea, and oolong tea all come from the same plant. Black tea is a traditional beverage in Britain. The quality of tea depends on the age of the tea leaves.
Black tea is a source of caffeine, which stimulates the heart and central nervous system, relaxes smooth muscle in the lungs, and promotes urination. One cup of tea contains about 50 milligrams of caffeine, depending on the strength and size of the cup, while coffee contains 65-175 milligrams of caffeine per cup. Tea also contains vitamins, a compound called tannin, and antioxidants called polyphenols.
There is conflicting evidence for the use of black tea in preventing heart disease and cancer. Regular tea consumption may lower the risk of heart attacks and all-cause mortality, regardless of age, sex, smoking status, obesity, and medical history. There is preliminary evidence for the use of black tea in increasing bone marrow density (BMD), preventing osteoporosis in older women, and enhancing brain and muscle function. The evidence is also preliminary for the use of black tea as a mouthwash in the prevention of dental cavities.
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These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Preliminary evidence suggests that adult asthma sufferers may benefit from drinking black tea or coffee. However, there is not enough evidence, and more research is needed before conclusions can be made.
Overall, there is conflicting evidence for the use of black tea in cancer prevention. Preliminary evidence suggests that there may be a link between tea consumption and cancer, although other results found that countries with significantly higher tea consumption did not have lower rates of death from cancer. Black tea has been studied for use in mouth, throat, stomach, pancreatic, and colorectal cancer, but results have been mixed. More research is needed before any conclusions can be made.
Dental cavity prevention
There is preliminary evidence to support the use of black tea as a mouthwash in the prevention of dental cavities. More studies are required to confirm this potential benefit.
Some studies suggested that instant black tea may lower blood sugar and increase insulin levels, compared to water and caffeine. However, results are conflicting, and further research is required.
Heart attack prevention / cardiovascular risk
There is conflicting evidence for the use of black tea for heart health problems. Some studies suggest that black tea may help prevent hardened arteries and heart disease, but the results are unclear. The effect on blood pressure is also not clear. Future studies may reveal more about black tea's effects on heart health.
There is preliminary evidence supporting the use of black tea in improving brain function and memory. Future trials are needed to compare the potential benefits of coffee, black tea, green tea, and caffeine supplements to determine safety and effectiveness.
Preliminary studies have examined the effects of caffeine, tea, or coffee use on short- and long-term memory and alertness. There is evidence to support the use of black tea in increasing mental alertness, but results are still unclear and more research is needed.
Methicillin-resistant Staphylococcus aureus (MRSA) infection
Preliminary research showed that inhaled catechin, an antioxidant found in tea, may be temporarily effective in treating a bacterial infection, MRSA, and may shorten length of hospital stay in elderly patients with this condition. However, results are unclear, and additional research is needed before conclusions can be made.
Oral leukoplakia/ carcinoma (white patches in mouth)
Early studies report that "mixed" tea smeared on leukoplakia patches may improve the condition and reduce DNA damage, thereby preventing mouth cancer. Further research is needed to confirm these results.
Preliminary evidence suggests that black tea may increase bone mineral density and help prevent osteoporosis in older women. More research is needed to confirm these findings.
Preliminary evidence suggests that tea consumption may improve feelings of relaxation and decrease levels of cortisol, a stress hormone. More well-designed studies are required before conclusions can be made in this field.
Black tea has been studied as an ingredient in many combination weight loss products. More well-designed studies are needed to understand the potential benefits of black tea for this purpose.