As far as I am aware there are three main causes of impotence and the associated problems such as having trouble maintaining an erection, premature ejaculation and low libido.

Firstly, a deficiency in minerals, especially of Zinc and Magnesium.
Good results have been obtained in some cases just by increasing these minerals – taken as Colloidal minerals (which are especially high in these two elements), along with extra vitamin B6 and B12.

Secondly, insufficient blood flow to the penis, which may be restricted for a variety of reasons including obesity, arteriosclerosis, smoking or stress.
The erectile tissues within the penis are called ‘corpora cavernosa’. These spongy tissues fill with blood on arousal, to produce an erection. The size and strength of the erection depends on how much blood the body pumps into the corpora cavernosa.
Most remedies are aimed at improving this function.

Many natural herbal combinations will contain herbs that have a long history of helping sexual dysfunction and on study have been found to work in
the main through their ability to improve the overall health of the body
and in some cases to increase testosterone levels and balance hormones.

Maca root, Yohimbe, Tribulus, Horny goat Weed, Macuna, Sarsaparilla and Ginseng are all examples of this type of herb.

Saw Palmetto is another herb that can have profound effect, its action being more on the prostate gland, but it can prove very effective in increasing, maintaining or even having an erection.
None of these herbs actually contain testosterone, the effect they have on the male hormones is in most probability created by the effect they have on the hypothalamus and the pituitary glands.

Maca is a root vegetable that is indigenous to Peru. It has long been used to increase fertility, sperm counts and mobility in males and improve conception in females. There are few scientific studies at this stage only centuries of successful use.

Tribulus, appears to increase the production of testosterone, regulate hormone balance and act as a rejuvenation tonic. To be effective high doses of the herb are required.
The recommended dose being 250mg of standardised concentrate, equivalent to 10gm of dried herb, containing 100mg of furostanol saponins, taken three times daily. For there to be sufficient furostanol saponins, the preparations need to be made with the above ground
parts of the plant.

Ginseng acts in a similar manner and also need to be taken in high doses to be effective. Around 2.5 – 5gm of root per day or the extract equivalants. Both these herbs are known as adaptogens which mean they act as tonics to the body as a whole and often help other remedies work more effectively.
Ginseng is also thought to help relax the smooth muscle of the penis which enables the blood to flow more freely.

Ginkgo is often included not because it increases testosterone but because it helps open up the very small capillaries and also enables blood to flow more easily.

Yohimbe is the inner bark of a West African tree and once again has long been used to improve sexual dysfunction. Its other uses are to help relieve anxiety and depression and to help build muscle tissue

Horny Goat Weed is part of traditional Chinese medicine and like Tribulus and Ginseng it has been found to increase testosterone levels and has the ability to improve sexual performance.

Another frequent component of these remedies is L-Arginine.
L-Arginine is an amino acid which is the precursor to the body synthesising nitric oxide. Nitric oxide in the body enables the arterial system to maintain its elasticity and in this way is involved in the production and maintenance of erections.
L-arginine is also required to help regulate blood flow and may in some cases help alleviate high blood pressure.
It is also used to improve fertility in men, and to improve the immune system

All these remedies will offer a milder but more natural and safer approach to improving sexual health.

In some cases, diabetes can be a factor as can some medications.

Some drugs used to treat hypertension, allergy, depression and reflux are known to cause erectile problems. If you suspect that this may be a factor in your case check with your GP. In these cases the under lying problems must be addressed and they are subjects in them selves.

Thirdly, emotional problems can be a big factor and are often made worse by the problem itself.
Stress, of any sort can have a very debilitating effect as can fatigue and depression. Emotional problems obviously need to be dealt with in their own context, however supplementing with minerals, vitamins and stress relieving herbs can play an important part in helping the situation.

In these situations the intake of alcohol, coffee and nicotine also often increases and all can be detrimental as they cause blood vessels to constrict and therefore restrict the flow of blood to the penis.