I've begun drinking rooibos tea (red tea - from South Africa) and it is creating a slight reduction in my blood pressure.  I am seeing it go from about the 142/65 down to around 128/55 level.  There is no other explanation for the drop.  I am doing a cup of the tea in the morning and a cup in the evening.  From what I can find on the Internet it is best to let it steep for at least 10 minutes.  I don't find much flavor to it, but it does have a slightly sweet taste.  I am also using it for iced tea, and take a bit of that during the day.

This is a caffeine free tea, with several benefits.  Here's a couple of links with more information.

http://oolongteaforweightloss.com/index.php/Home/Types%20of%20Teas/Rooibos%20Tea

http://www.cookscorner.net/Tea/Info_Rooibos.html