Most men occasionally struggle to get or keep an erection due to stress, tiredness, anxiety or drinking too much alcohol. The National Institutes of Health reports that around 30 million men have erectile dysfunction, with it being most common among the elderly. It can be caused by high blood pressure or cholesterol, hormone problems or side effects from medication. Some younger men also suffer from 'performance anxiety', where mental distractions and other issues have give them trouble Medicines containing sildenafil, the active ingredient in Viagra, are often used to treat the condition. It expands blood vessels and boosts blood flow...