The slower process of brewing in cold water results in a simpler and purer extraction than hot brewing. When you bring your dried tea leaves in contact with hot or boiling water, they’re extracted much faster and more completely, but this process also transforms some of the active ingredients as it extracts them.
Cold brew teas have been shown to have lower levels of caffeine, reduced bitterness, and heightened aroma. Because they’re chemically different, cold brew teas may also have a slightly different flavor profile which for many teas results in a smoother and less astringent taste.
The antioxidant levels in fresh cold brewed teas are the same or better (especially in the case of white tea) than fresh hot brewed teas.