Is Chinese herb Fo Ti really effective for impotence?

Condition analysis:
This herb has been used in traditional Chinese medicine since the Tang dynasty. Its Chinese common name, he-shou-wu, was the name of the man who purportedly was healed of his infertility after taking this herb.

This herb helps reduce fatty deposits in the blood and improves circulation, thereby helping erectile function. Some people have sensitivity to fo-ti and may develop a rash. Taking large amounts, more than 15 grams, may cause numbness in the arms and legs.

Instructions: 
1. Cnidium (Cnidium monnieri): Cnidium Monnieri has been used for erectile dysfunction treatment in Chinese herbal medicine since ancient times.

The main active substance present in the herb is osthole which is thought to work in similar manner as to Sildenafil in Viagra.

Osthole has been shown to affect the spongy tissue and blood vessels in the penis. It dilates and relaxes the blood vessels allowing for enhanced blood supply to the spongy tissue of the penis which in return can result in stronger erections.

2. Muira Puama (Ptychopetalum olacoides ): A Brazilian shrub that has been used in South America for centuries as an aphrodisiac and to stimulate the nerves. Considered by many as the best impotence herb available and in some clinical studies it has proven to be effective as a treatment for erectile dysfunction in some men. But as with many other medicinal herbs, more studies are needed.