Black, green, and oolong tea are the three main categories of tea consumed in the world. Tea provides a variety of flavonoids and antioxidants as well as a few micronutrients, in particular fluoride. While there is solid evidence that tea protects against chemically-induced cancers in experimental animals, it remains unclear whether tea consumption lowers cancer risk in humans. Tea also provides some amino acids, of which the majority is theanine. Recently, theanine has been shown to enhance innate immunity - the body’s ability to resist infections - by stimulating gamma-delta T cells and this effect has been replicated with regular (5-6 cups/day) tea consumption in humans. Tea consumption may also increase bone density, reduce tooth decay and cavities, and reduce kidney stones.

Coffee: Several prospective cohort studies have observed significant inverse associations between regular coffee consumption and the risk of type 2 Diabetes. High intakes of coffee have been associated with significant reductions in colorectal cancer risk in numerous case-control studies, but prospective cohort studies have not generally observed such significant associations. Coffee and caffeine consumption have been consistently associated with significant reductions in the risk of Parkinson’s disease in men but not women, which may be due to the modifying effects of estrogen. Unfiltered coffee should not be consumed—that is coffee directly boiled.
The Panel recommends that coffee (unsweetened) be consumed up to 400 mg/day or about 32 fl. oz./day of coffee. Caffeine is the limiting factor

Caffeine intake: There are greater amounts of caffeine in coffee than tea. At this time, in healthy adults the preponderance of evidence suggests that moderate caffeine intake up to 400 mg/d is not associated with increased risk of heart disease, hypertension, osteoporosis or high cholesterol. Some people are more sensitive to caffeine's effects than others and may feel effects at lower doses. Pregnancy and aging may affect one's sensitivity to caffeine. Pregnant women are often advised to limit caffeine consumption because caffeine intakes higher than 300 mg/d have been associated with increased risk of miscarriage and low birth weight. Interestingly, a variety of investigations report an “inverted U” relationship when a physiological or psychological response is plotted versus caffeine intake in a graph. That is, the magnitude of caffeine’s effect is smaller at low and high levels, but greater at intermediate levels. This relationship has been reported for the effects of caffeine on exercise performance time, reaction time, vigilance, information processing and mood state.

See table below for calorie and caffeine contentprocessing, and mood state but may not exist for all physiological and psychological response

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