Black tea is a heavier oxidized form of tea compared to the other teas available, such as oolong and green tea. It is the most consumed and enjoyed tea globally. Black tea has several effects, some of them neutral and some of them beneficial towards health. Black tea typically contains more caffeine than other teas, giving it a stronger energizing effect compared to other teas. Black tea, like other teas, is low in calorie, protein, sodium, and fat. The amount of carbohydrates in tea is almost minimal as well (usually less than 1g per serving). Each serving typically also has plenty of antioxidants, which have been shown to have anti-cancer and DNA-healing effects via neutralization of free radicals.
The health effects of black tea drinking are also real and exist. Recent studies have shown a correlation between tea drinking and reduce cardiovascular disease events, such as acute myocardial infarction and stroke. A study conducted by Boston University in 2001 concluded that this effect was due to components in black tea reversing endothelial vasomotor dysfunction, reducing the possibility of dangerous cardiovascular events. In addition, a compound known as theaflavin-3-gallate has shown promise in reducing the incorporation of cholesterol into mixed micelles. These micelles are responsible for absorbing cholesterol into the body, and blocking such an event may help with cholesterol levels, even if in modest levels. However, to gain these benefits, black tea must be drunk without milk. A German study in 2006 showed that milk cancels out these health benefits. This is likely because the casein proteins in milk bind to the active components in tea that have the purported health benefits. Plus, a study conducted by the University College London has shown black tea can reduce levels of cortisol and blood clotting activity (high levels may predispose towards a heart attack during a stressful condition) after a stressful event. Black tea has also been linked to reducing the incidence of diabetes and boosting immune systems, but have not been thoroughly investigated yet.