Black tea is also rich in theophylline, a substance similar to the one just described which is used - in much higher concentrations - in the treatment of asthma and bronchitis.
Theophylline, in fact, promotes bronchial dilation, improving - among other things - the contractility of the diaphragm and other respiratory muscles.
Black tea, like other varieties, is also rich in polyphenols.
Polyphenols are nutritional factors with antioxidant action, which prevent cardiovascular diseases and tumours.
Black tea also contains tannins, which have many of the metabolic characteristics of generic polyphenols.
In addition, tannins boast astringent properties because they reduce glandular secretion in the intestine by fighting diarrhea.