A study by Italian scientists has shown that a daily supplement of vitamin D improves erectile function and testosterone levels.

The scientists were looking into the effects of Vitamin D deficiency on the libido. Vitamin D deficiency, which has been associated with types 1 and 2 diabetes and Addison's disease, is also believed to have a detrimental effect on men's sex lives.

The study, published in the International Journal of Endocrinology, shows that a lack of vitamin D leads to erectile dysfunction and that a vitamin D supplement can help curb the problem. It also found that a regular vitamin D intake was associated with a rise in testosterone levels in men.

The cases of 114 men aged 60-68 who had been treated by the research team for erectile dysfunction in 2003 were re-evaluated. Sixty per cent of the participants suffered from type 2 diabetes, 51% had hypertension, 68% smoked and another 53% had an abnormal amount of fat in their blood - also called dyslipidemia.

The team first assessed the participants' sexual performance using the International Index of Erectile Function (IIEF), which is based on five criteria: how easy it is for a man to get an erection, how satisfied a man is with his penis during sexual intercourse, the state of his libido, whether he can reach orgasm during sex, and how satisfied he is with his sexual function overall.

Once assessed, 41 of the participants were subjected to tests before adopting a regimen of vitamin D supplements weekly or monthly. They underwent the same tests up to nine months afterwards.

Results show that the vitamin D treatment helped improve erectile function and increased testosterone levels in all patients. It also improved all other aspects of the IIEF. According to the results, men who had higher testosterone levels tended to be more happy with their sexual function and experienced less instances of erectile dysfunction.

The results stressed a strong connection between a man's level of testosterone and sexual problems, ranging from erectile dysfunction to poor libido.

The study also revealed that participants who suffered type 2 diabetes or smoked were found more likely to have lower testosterone levels than those who did not.