No, tea alone does not contain any calories.

No, tea does not contain gluten.

Tea never goes bad but the flavor will fade over time.  Store tea in air-tight containers in a cool, dark and dry place.

Yes, tea leaves come from the Camellia sinensis plant.  They contain antioxidants that counter free radicals which can damage cells.  Antioxidants may reduce or help prevent some of this damage.  Let tea steep for 3 to 5 minutes to get the most antioxidants from tea.

There are three main varieties of tea, green, black and oolong.  Black tea is exposed to air or fermented which darkens the leaves and gives them flavor.  Green tea is made by heating or quickly steaming the leaves. and Oolong tea leaves are partially fermented.