According to the Academy of Nutrition and Dietetics, black, green and oolong tea all contain caffeine. To compare, one cup of coffee contains about 95 milligrams of caffeine with the same amount of black tea containing 48 milligrams, oolong tea containing 38 milligrams and green tea containing 29 milligrams. Decaffeinated black, green and oolong teas contain very small amounts of caffeine, and many herbal teas are caffeine-free.
Natural substances, called polyphenols, are found in caffeinated and herbal teas. These substances are antioxidants, compounds that may help reduce the risk of certain chronic diseases. During processing, some of the polyphenols in tea are destroyed. Thus, tea powders, decaffeinated teas and bottled tea drinks may not offer the same health benefits. Additionally, research suggests that green teas offer a greater antioxidant punch compared to most other varieties.
Though the jury is still out, some studies suggest the caffeine and catechins, a type of polyphenol, in tea may help with weight loss. Decaffeinated green teas did not appear to produce the same results. Though the research on caffeinated green tea looks promising, there are still a lot of unanswered questions. Plus, the results have been minimal — only one to two pounds of additional weight loss. Also of note, research is lacking to support the wide range of herbal tea products advertised for weight loss and these can be harmful depending on their ingredients.
Some research has shown a reduced risk of heart disease in people who drink green or black tea regularly; although the findings have been mixed in terms of tea’s effect on lowering cholesterol and blood pressure.
The research relating to diabetes is less clear. Some studies suggest the catechins in green tea may help to keep blood sugar in check, reducing the risk for developing Type 2 diabetes. However, these findings have mainly been based on practices in other countries and not repeated in clinical trials. Researchers are also evaluating if spearmint and chamomile herbal teas have a role to play in preventing diabetes. More research is needed on the amount of tea and type of tea, especially since some of the results have involved tea in the form of a supplement instead of a drink.
Though there is lots of information online about tea as a cancer-fighting beverage, research has not proven that consuming tea helps to reduce the risk of cancer. At this time, it is unknown if tea drinking can reduce your risk of cancer.
Though there are lots of good things about consuming tea, overdoing it can put your health at risk. One risk is a caffeine overload. Large amounts of caffeine may lead to nervousness, restlessness and may disturb your sleep. Some people may also experience gastrointestinal issues, nausea, abdominal pain, heartburn, dizziness and muscle pain. It may also interact with certain medications and increase the effects of caffeine in the body. Total daily intake of caffeine from all sources should not exceed 400 milligrams.
Although more research is needed to pin down all of its benefits, tea can be part of a healthy eating pattern. For the most powerful punch, steep your own tea and be mindful of how it is sweetened in order to limit sources of added sugars.