The researchers noted that "when patients were stratified according to the baseline severity of ED, the patients with moderate and severe ED who received niacin showed a significant improvement in IIEF-Q3 scores (0.56 0.96 [P = 0.037] and 1.03 1.20 [P < 0.001], respectively) and IIEF-Q4 scores (0.56 1.03 [P = 0.048] and 0.84 1.05 [P < 0.001], respectively] compared with baseline values, but not for the placebo group...For patients not receiving statins treatment, there was a significant improvement in IIEF-Q3 scores (0.47 1.16 [P = 0.004]) for the niacin group, but not for the placebo group. Niacin alone can improve the erectile function in patients suffering from moderate to severe ED and dyslipidemia." 
One of the keys to addressing erectile dysfunction is improving the functioning of the endothelium, which is the inner lining of blood vessels. Wayne Hellstrom, MD, urology professor at Tulane University School of Medicine says keeping endothelium healthy can help you improve erectile functioning. Cardio training helps with this, as does resistance training. Adding weight training to cardio training increases muscle mass and bone strength helps your balance and stability (which can help prevent injuries) and can help lower blood pressure as well. Improved muscle definition can also be great for self-esteem, and that can’t hurt.
According to a study conducted by the University of the West of England, Bristol, pelvic floor exercises may be very effective in treating erectile problems. Many participants of the study, all of whom were men who had been experiencing erectile dysfunction for at least six months, reported a significant improvement of their condition within three months of training their pelvic floor.
In the present study zinc caused an elevation of T. This showed an increase from 2.39 to 8.21 ng/dl after two weeks of zinc treatment. This elevated T level may have contributed to the increase in number of penile thrusting (from 26.5 to 52.8) observed. Supplementation with 459 μmol/day of zinc for three months, in marginally zinc deficient healthy elderly men, has been shown to increase the levels of serum T from 8.3 to 16 ng/dl. Laboratory experiments indicate that the nitric oxide erectile pathway is T dependent. Many studies using animal models have confirmed that T is important in modulating the central and peripheral regulation of erectile dysfunction. T deprivation has a negative impact on the structure of penile tissues and erectile nerves. Thus, elevated T levels subsequent to zinc supplementation may increase the sexual competence via rigid and sustained erection. This may promote greater tactile stimulation of the penis due to increased contact with vagina.
Even at the higher doses of yohimbine, no changes in blood pressure or pulse were noted. This agent would appear to be safe in men with medically controlled hypertension. There was an increase in the morning cortisol levels in all men; the value was higher but not significantly so in responders. Telöken et al18 reported a high percentage (80%) of adverse events, but these authors administered a large dose (100 mg) of yohimbine. A toxic overdose of 200 mg produced only tachycardia, elevated blood pressure and anxiety of brief duration.33 Even direct intravenous dosing of yohimbine raised the mean arterial blood pressure by 12%,34 Goldstein et al35 systematically administered yohimbine and noted large hemodynamic and norepinephrine responses in both normal and hypertensive men; only the men who had a history of anxiety, depression, or other psychopathologic factors had symptoms. Oral administration of yohimbine at standard doses or even four tablets (21.6 mg) at a time has had no effect on blood pressure.4 Elevated blood pressure and heart rate were recorded when eight tablets (43.2 mg) were given at one time.3
The key to all of this is the endothelium, the inner lining of blood vessels that helps blood flow smoothly. Regular exercise has been shown to improve the way the endothelium works. The endothelium lines the blood vessels in the heart and the penis, explains Dr. Hellstrom, but the blood vessels in the penis are about one-third the size of those in the heart. So if you fail to have erections due to vascular problems, that indicates that you’re at risk for heart problems as well.