A daily dose of niacin improves erectile function, particularly in men with high cholesterol, according to a 2011 study in The Journal of Sexual Medicine. The vitamin helps increase blood flow and reduce inflammation—one of the underlying causes of both high cholesterol and erectile dysfunction. “Vitamin B3 is also used to make sex hormones and other important chemical-signal molecules,” says Fisch. Like many of the others on our list, this tablet is most powerful when taken in conjunction with others: A cocktail of propionyl, L-carnitine, L-arginine, and niacin taken for three months improved 40% of erections in a study from researchers at Sapienza University of Rome in Italy.
The neurovascular mechanism of erection is complex and involves multiple factors including hormones, neurotransmitters, elements of the autonomic nervous system (sympathetic and parasympathetic) and vasodilators such as NO. The common causes of ED include psychogenic disturbance with failure to relax cavernous smooth muscle, arterial insufficiency as a result of atheromatous disease, damage to the parasympathetic nervous system, spinal cord injury, diabetes or following pelvic surgery such as radical prostatectomy, radical cystectomy or bowel resection [4]. It is important to note that cavernous nerves are unique in that although they belong to the autonomic nerves system they do not release either acetylcholine (Ach) or norepinephrine; however, they release NO in the penis. NO relaxes the smooth muscle of the corpora cavernosa via cyclic GMP (cGMP), allowing expansion of the cavernosal lacunar spaces, blood flow and erection. Thus, NO is not a direct dilator of the smooth muscle of cavernosal bodies, but it is an important mediator in this process. Erectile function may also be adversely affected by cigarette smoking, excess alcohol consumption, obesity and systemic diseases such as mononucleosis, hepatitis, HIV and cancer. Some men are prone to develop an erection that fails to subside after ejaculation (ie, priapism). The condition is associated with sickle-cell disease and leukemia, or may be a result of intracavernosal injection of drugs such as prostaglandin E1 [4]. Peyronie’s disease causes a physical bend in the erect penis and also contributes to ED.
The Plant: It’s true, the name’s hilarious. But as it turns out, it’s not just one plant: supplement manufacturers might put any one of 15 different species from this genus of shade-loving perennials inside that pill. That’s important to keep in mind, because the types and amounts of biologically active molecules the plant contains can differ from species to species.

Yohimbe A number of clinical trials have shown that the primary component of this bark from an African tree can improve sexual dysfunction associated with selective-serotonin reuptake inhibitors (SSRIs) used to treat depression. This herb has been linked to a number of side effects, including increased blood pressure, fast or irregular heartbeat, and anxiety. Yohimbe shouldn't be used without a doctor's supervision.