Green tea is remarkable: it reduces heart disease risk, cancer risk and overall mortality. But what about the more common, at least to us Americans, black tea? Does black tea help or hurt the heart? brain? erections?
The answer to that is not as simple as it sounds. Black tea is known to be loaded with polyphenols and phytochemicals that promote health. Unfortunately, the fermentation process that black tea goes through converts almost all of the EGCG (contained in green tea) to other less effective compounds.
Nevertheless, black tea is powerful stuff with significant superpowers and one meta-analysis found solid evidence that if three or more cups were consumed per day cardiovascular risk would be significantly reduced.  Furthermore, it likely provides protection against a host of ills due to its blood glucose-controlling powers. 
What about erections? Will black tea help your sex life? This has never been directly studied as far as I know, but the answer is undoubtedly 'yes'. The reasons are:
1. Caffeine. Caffeine is a mild PDE5 inhibitor, i.e. is Viagra or Cialis Lite.
2. Endothelial Function. Erections are all about the endothelium, the delicate lining of your blood vessels and arteries that pumps out that precious nitric oxide for erectile strength. Black tea has been shown to improve endothelial dysfunction in heart disease patients and even improved blood flow.  Almost everyone in a modern society will have a certain amount of heart disease.
3. Blood Flow. The same study above  found that "flow mediated dilation" was significantly improved as well. Translated, this means improved blood flow and improved blood flow will almost always translate to a more powerful erection. And lest you think this applies only to those plagued with major cardiovascular issues, another study found improved blood flow in healthy male volunteers. 
Now I love black tea - it's probably my favorite day-to-day beverage, yet I am very cautious about it. Why? The reason has nothing to do with the heart or penis but rather the brain. Scientists have always know that flouride tends to accumulate in black tea and believe that this is the reason that it likely has not done very well in cognition and brain-related studies.
Fluoride, as it turns out, is very hard on the brain and caused increased oxidation and cell death.  It also worsens the effects of aluminum in the brain , another very common dementia-related element.
Of course, the question, when it comes to flouride, is dosage. Does black tea have enough flouride to merit concern. It has long been known that instant tea accumulates enough flouride to even cause troubles in the short term, but scientists did not know what to think about regular black tea over long time periods.
A recent study raised even higher levels of concern when researchers found that black tea contained much higher levels of flouride than previously thought. Previous studies had shown 1 to 5 mg/liter of fluoride in black tea but the level was actually found to be about 9 mg/liter.  This level is high enough to cause concern because it could lead to bone and skeletal issues, another issue with fluoride consumption, for heavy tea drinkers. And if it is causing bone issues, it will simultaneously be wreaking havoc with your neurons as well.
So, for the sake of your brain, black tea is definitely a drink that should be consumed in moderation and some researchers might even argue sparingly. Green tea is much safer and more powerful alternative.
1) European Journal of Clinical Nutrition, 2007, 61:3ï¿½18, "Black tea ï¿½ helpful or harmful? A review of the evidence"
2) Circulation, 2001, 104:151ï¿½156, "Short- and long-term black tea consumption reverses endothelial dysfunction in patients with coronary artery disease"
3) Am J Cardiol, Jun 1 2004, 93:1384ï¿½1388, "Black tea increases coronary flow rate velocity reserve in healthy male subjects"
5) Toxicology, Jul 17 2007, 236(3):208-216, "Effects of fluoride on the expression of NCAM, oxidative stress, and apoptosis in primary cultured hippocampal neurons"
6) Archives of Physiology and Biochemistry, 1999, 107(1):15-21, "Fluoride Enhances the Effect of Aluminium Chloride on Interconnections Between Aggregates of Hippocampal Neurons"