Vitamins   Tea is a beverage that is demonstrably not particularly rich in vitamins – that goes for both black and green varieties. The vitamin C content of green tea is higher, but can hardly contribute to the daily vitamin intake. Furthermore, vitamin C (ascorbic acid) is not particularly heat-stable and becomes inactive at about 80°C. Group B1 and B2 vitamins are also available in small quantities. However, tea contains comparatively high amounts of fluoride, potassium, and manganese.