The Science Behind Tea
Tea, derived from the *Camellia sinensis* plant, boasts a complex biochemical profile that contributes to its diverse health effects. While macronutrient content is negligible (virtually zero calories from carbohydrates, fats, or proteins), the true power lies in its micronutrients and bioactive compounds. The most prominent of these are polyphenols, specifically flavonoids like catechins, theaflavins, and thearubigins, which are powerful antioxidants. Clinical studies show that these compounds scavenge free radicals, reducing oxidative stress and potentially protecting against cardiovascular disease, cancer, and neurodegenerative disorders.
The micronutrient profile varies depending on the type of tea and brewing method. Black tea contains manganese (around 10% of the daily recommended intake per cup) and potassium (around 2% of the daily recommended intake per cup), which are essential for bone health and electrolyte balance, respectively. Green tea, on the other hand, is particularly rich in vitamin C and vitamin K, supporting immune function and blood clotting. White tea, processed the least, often retains the highest antioxidant content.
Caffeine is a significant component of tea, acting as a stimulant that enhances alertness and cognitive function. The caffeine content varies widely, with black tea typically containing the most (40-70mg per cup), followed by oolong tea (30-50mg per cup), green tea (20-45mg per cup), and white tea (15-30mg per cup). Decaffeinated varieties are also available, offering the antioxidant benefits without the stimulating effects.
Regarding digestion, tea is generally well-tolerated. However, the tannins present in tea can bind to iron in the digestive tract, potentially inhibiting its absorption. This is particularly relevant for individuals with iron deficiency. Adding lemon to tea can improve iron absorption, as vitamin C counteracts the effects of tannins.
Tea's impact on metabolism is mainly attributed to its caffeine and polyphenol content. Caffeine can increase metabolic rate and fat oxidation, while catechins like EGCG have been shown to enhance energy expenditure and promote weight loss in some studies. Nutrition research indicates that regular green tea consumption may contribute to improved insulin sensitivity and glucose control, potentially benefiting individuals with diabetes or insulin resistance. However, these effects are often modest and depend on individual factors such as genetics, diet, and lifestyle.
