The Science Behind Tea
Tea, primarily derived from the *Camellia sinensis* plant, is a complex beverage with a rich chemical composition. It's virtually calorie-free when consumed without added milk or sugar. Macronutrient-wise, tea contributes negligible amounts of carbohydrates, fats, or proteins. Its significance lies in its micronutrient and bioactive compounds.
**Micronutrients:** Tea contains trace amounts of minerals like manganese (essential for bone health and enzyme function), potassium (important for maintaining electrolyte balance and blood pressure), and fluoride (beneficial for dental health). The concentration of these minerals varies depending on the type of tea and the growing conditions.
**Bioactive Compounds:** The most prominent bioactive compounds in tea are polyphenols, specifically flavonoids like catechins, including epigallocatechin gallate (EGCG), epigallocatechin (EGC), epicatechin gallate (ECG), and epicatechin (EC). These compounds are potent antioxidants, protecting cells from damage caused by free radicals. Clinical studies show that EGCG, in particular, exhibits anti-inflammatory, anti-cancer, and cardioprotective properties.
**Tannins:** Tea also contains tannins, which contribute to its astringency and can interfere with iron absorption. The higher the tannin content, the more likely it is to bind to iron in the digestive tract, reducing its bioavailability. This effect is more pronounced with black tea compared to green or herbal teas.
**Caffeine:** Tea contains caffeine, a stimulant that can enhance alertness, improve cognitive function, and boost metabolism. The caffeine content varies depending on the type of tea, brewing method, and steeping time. Black tea generally has the highest caffeine content (around 40-70mg per cup), followed by oolong tea (30-60mg), green tea (20-45mg), and white tea (15-30mg). Decaffeinated tea contains minimal caffeine (less than 2mg).
**Digestion and Metabolic Impact:** Tea, in its purest form, has a negligible Glycemic Index (GI). It doesn't significantly raise blood sugar levels. However, adding sugar or honey will increase its GI. The polyphenols in tea can positively influence metabolism by increasing energy expenditure and promoting fat oxidation. Nutrition research indicates that EGCG can enhance the activity of enzymes involved in fat metabolism. Consuming tea on an empty stomach can increase gastric acid secretion. The tannins and caffeine can also irritate the stomach lining in sensitive individuals. However, for those who tolerate it well, the enhanced focus from caffeine and the potential metabolic boost from polyphenols may be beneficial. The speed of digestion of plain tea is very rapid due to the lack of macronutrients. Therefore, drinking it before a workout can provide a quick energy boost (if caffeine is desired and tolerated). Adding milk will slow digestion somewhat due to the introduction of protein and fat.
