The Science Behind Green Tea
Green tea, derived from the Camellia sinensis plant, is renowned for its rich composition of polyphenols, particularly catechins, with epigallocatechin gallate (EGCG) being the most abundant and potent. These catechins are powerful antioxidants, neutralizing free radicals and reducing oxidative stress within the body. A typical cup (8 ounces) of green tea contains approximately 30-50 mg of caffeine, significantly less than coffee (95-200 mg per cup). However, this caffeine content can still stimulate the central nervous system, increasing alertness and potentially interfering with sleep. Nutrition research indicates that green tea is virtually calorie-free, containing negligible amounts of macronutrients like carbohydrates, fats, and proteins. It provides trace amounts of minerals like potassium, fluoride, and manganese, contributing to overall health. Clinical studies show that the antioxidants in green tea can improve cardiovascular health by reducing LDL cholesterol levels and blood pressure. The GI index of green tea is essentially zero due to its lack of carbohydrates, making it a suitable beverage for individuals managing blood sugar levels. Digestion speed is rapid, with the liquid being quickly absorbed into the bloodstream. The metabolic impact is primarily driven by the thermogenic effects of catechins, which can slightly increase energy expenditure and fat oxidation. The presence of L-theanine, an amino acid unique to tea, promotes relaxation without drowsiness by increasing alpha brain wave activity. However, the caffeine can counteract these effects, especially close to bedtime. The caffeine half-life in the body ranges from 3 to 7 hours, meaning that half of the caffeine consumed remains in your system for that duration. Therefore, drinking green tea late in the day can significantly impact sleep quality and latency.
