Any hard data on this?
[If so, do the health benefits] apply to all kinds of teas and coffees?
What about decaf varieties?
— Corey Clark
There is plenty of data in the scientific literature showing the health benefits of coffee.
Coffee beans contain a wide array of antioxidants, polyphenols, and health-promoting compounds.
Additionally, the antioxidants in coffee have been shown to reduce inflammation and inhibit cellular tumor growth.
What these studies basically show is that healthy individuals (although not pregnant women) who drink coffee regularly do not need to be concerned with cutting it out of their diet for health reasons.
That said,the percentage of the population that is sensitive to caffeine should certainly avoid it.
Luckily, both caffeinated AND decaffeinated coffees and teas share the same amount of flavonoids and antioxidants.
Speaking of teas, all varieties (green, white, and black) offer plenty of flavonoids and antioxidants. Herbal teas, however, offer significantly lower amounts.
The biggest issue with these beverages is what people are putting into them (syrups, tablespoon upon tablespoon of sugar, mounds of whipped cream, etc.) that often turns them into calorie, sugar, and fat-laden drinks that do more harm than good.