A new popular way of making tea is to steep leaves in cold water.
The study authors investigated whether antioxidant activity of teas is affected by hot or cold water steeping and if this correlates with their polyphenol content and metal-chelating activity.
A set of five loose tea samples, consisting of unblended and blended teas, was analysed following infusion in either hot water (90 °C, 7 min) or cold water (room temperature, 2 h).
Antioxidant activity, measured as hydrogen-donating ability, showed no significant differences among hot or cold teas, except in the case of white tea, where higher values were obtained after cold water steeping.
The antioxidant activity of the teas correlates with their phenolic content and metal-chelating activity. Cold teas were better inhibitors of in vitro LDL conjugated diene formation.
The authors concluded that the potential health benefits of tea may be maximised by methods of preparation.
According to BMJ, drinking hot tea may cause cancer:
"Sip green tea all day; green tea usually contains about 25 percent as much caffeine as coffee and provides a steady stream of antioxidants." -- "Drink coffee for breakfast, tea in the afternoon, wine at 5 p.m." Source: http://www.npr.org/blogs/thesalt/2015/04/28/400156651/tea-tuesdays-tea-drinking-tips-for-a-longer-life
Hot vs. cold water steeping of different teas: Do they affect antioxidant activity? Elisabetta Vendittia, Tiziana Bacchettia, Luca Tianoa, Patricia Carlonib, Lucedio Grecib and Elisabetta Damiania. Food Chemistry, Volume 119, Issue 4, 15 April 2010, Pages 1597-1604. Green Tea Decreases Total and LDL Cholesterol by 5 mg/dL http://goo.gl/AwVDr and http://goo.gl/Ku55O
BMJ Video: Drinking hot tea may cause cancer
Coffee vs. Tea - Infographic of Health Benefits and Risks http://goo.gl/StIsr
What's in Your Green Tea? Loose tea leaves are perhaps the best and most potent source of antioxidants http://buff.ly/1avSe3p
Image source: Green Tea leaves in a Chinese gaiwan. Wikipedia, Wikimol, Creative Commons Attribution ShareAlike 2.5 License.