Can the ancient herb Ginseng improve erectile dysfunction? Yes, Ginseng can potentially improve your sex life and erections in many ways. Ginseng is best known in herbal lore as an "adaptogen", meaning that it helps overcome stress and stress-induced reactions. Of course, it is also known as an energy booster and is added to a host of "energy drinks".
However, Ginseng's benefits in these are debatable at best with a number of studies showing contradictory results. But there is one place where Ginseng does have some have some strong initial evidence: improving erectile dysfunction. It turns out that Korean Ginseng does boost nitric oxide output and, if you guessed that that means improvements in erectile dysfunction, you'd be right. Several studies have shown Ginseng to improve erectile dysfunction.
For example, one well done 2002 double-blind, placebo-controlled, crossover study done in Korea looked at 45 men with moderate to severe erectile dysfunction. It took only 8 weeks for improvement in the scores on erectile performance, sexual satisfaction and other key measure for those men using Ginseng.  A similar study five years later on 60 men with erectile dysfunction found significant improvement in just 12 weeks in the areas of "rigidity, penetration and maintenance of erection" when patients were treated with three times daily routines of 1000 mg of Ginseng. 
Ginseng likely does this through several pathways with the most direct being stimulation of nitric oxide production.  Of course, nitric oxide is the magic chemical that relaxes your penile arteries and allows blood to flow in. Any increase in nitric oxide will likely improve erectile dysfunction and put a smile on your and your partner's face.
What are the odds that Ginseng can improve your erectile dysfunction? One older study showed that 60% of men were satisfied with sex and firm erections with Ginseng as opposed to 30% without.  This is almost two thirds of the participants that were helped by Gingeng! The study authors summarized by saying that "in the group receiving ginseng, changes in early detumescence and erectile parameters such as penile rigidity and girth, libido and patient satisfactions were significantly higher than that of other groups". In other words, improvements were so strong that the actual thickness of the erect penis and the "hardness factor" were actually improved. What else could you ask for, eh?
The story gets even better, though, in one animal study of diabetic rats. Normally, diabetic rats have significantly depleted levels of key antioxidants, such as glutathione, that protect the lining of the arteries within the penis and therefore have significantly more erectile dysfunction. However, the diabetic rats given Korean Ginseng had not only greatly improved antioxidant levels but also had no loss of erectile function.  Of course, this was an animal study, but it probably means that Ginseng not only helps with erectile dysfunction in the short term but in the long term as well. And notice that this study shows that it increases libido - woo hoo! - as well. (See my link on Aphrodisiacs for legitimate libido boosters to help with erectile dysfunction.)
Another way that Ginseng may in some case improve erectile dysfunction is through stress mediation. Stress can hammer mood, confidence and even testosterone in some cases. However, the studies are certainly not conclusive in this area and Ginseng probably has either a selective or subdued stress-reducing role.
Does Ginseng increase testosterone? Ginseng can help with cAMP levels, which, according to one study, boosted hormone, LH and DHT levels in men with low sperm counts.  However, one study show that testosterone (and growth hormone) levels are not significantly raised by Ginseng, thus eliminating the possibility that Ginseng helps with erectile dysfunction through a hormonal route.  I have never read of any bodybuilder, for example, using Ginseng to boost testosterone.
Are there any cautions associated with Ginseng in treating and/or helping with erectile dysfunction? The active ingredients, ginsenosides, in Ginseng are structurally similar to both testosterone and estrogen. In women Ginseng does have some reported estrogenic qualities. For example, one study found that a particular line of breast cancer cells that are estrogen-sensitive were made worse with Ginseng.  However, one animal study  and one human study on males  have shown an increase in testosterone with Ginseng, although still others have shown no such increase.  It is likely, however, that Ginseng has minimal effect on either testosterone or estrogen since it has been used for centures with few hormone-related side effects reported.
So the bottom line, as I document in my link on Super Sexual Herbs, is that Ginseng will very likely give most guys a nice boost in nitric oxide and libido and perhaps a small boost in testosterone as well.
Some Ginseng supplement manufacturers are sloppy and thus Ginseng has a reputation for having contaminants, including lead and various pesticides. Thus, buying only the best brands is definitely wise. For example, Consumer Labs failed 45% of tested products in a recent review for either having insufficient ginsenosides or being contaminated. However, a number of brands passed Consumer Labs' analysis with flying colors. Probably the best was Solgar - Korean Ginseng Root Extract, 60 veggie caps which was not only contaminant-free but also had abundant ginsenoside content.
CAUTION: Ginseng does have a few drug interactions (blood thinners, etc.) so check with your doctor first as always.
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