The Science: Some studies have implied that feeding maca to domestic cattle increases sperm production, but there is very little data about any sexual effect on humans. One very small randomized double-bind trial of men with erectile dysfunction found that men taking maca extract reported a small increase in their ability to get erections. But so did the control group. As with the fenugreek study, a similar study with a larger group of people is needed to see whether any differences between the controls and the maca-eaters are real.
Most importantly, herbal supplements are not well regulated in the United States.  Studies have shown that 40-50% of herbal supplements do not even contain the supposed main ingredient, and many contain substances that are not listed which may have dangerous side effects2.  Another study found that over two thirds of the products tested had substituted other plant species for the plants listed on the label, and a third of products also contained other fillers or contaminants3.  A study by the New York State Attorney General of herbal products sold at GNC, Target, Walgreens, and Walmart found that four out of every five products didn’t contain the ingredient they claimed!  Fourteen US states and territories have petitioned Congress to regulate the herbal supplements industry.
Currently, there are four orally active drugs are available to treat ED. These include: sildenafil citrate (Viagra [Pfizer, USA]), vardenafil hydrochloride (Levitra [Bayer, Germany]), tadalafil (Cialis [Eli Lilly, USA]) and avanafil (Stendra, Spedra [Vivus Inc, USA]). These drugs inhibit the enzyme phosphodiesterase type 5 (PDE-5), which is responsible for the hydrolysis of cGMP. PDE-5 inhibitors and cGMP act as effectors of dilation of smooth muscle of cavernosal bodies. PDE-5 inhibitors are contraindicated in patients taking any kind of nitrate therapy for angina, and may not be appropriate for men with certain health conditions, such as severe heart disease, heart failure, history of stroke or heart attack, uncontrolled high blood pressure or diabetes, and patients with pigmental retinopathy. PDE-5 inhibitors are less effective in men with diabetes and men who have been treated for prostate cancer. PDE-5 inhibitors are also not effective in men with retinitis pigmentosa, a genetic disease involving PDE-5 deficiency. The common side effects of PDE-5 inhibitors include gastrointestinal upset, headache, nasal congestion, back pain and dizziness. The PDE-5 inhibitors may interact with other medications including antihypertension drugs. Nonetheless, the PDE-5 inhibitors are generally safe and effective for most men. The primary mechanism of action of these drugs is through the mediation of NO. NO is one of the key molecules involved in ED. It is a short-lived, highly permeable, pleiotropic, gaseous molecule, secreted from the postganglionic cavernosal parasympathetic nerves, endothelium of the cavernosal blood vessels, platelets in the cavernosal sinuses and phagocytic cells (monocytes, macrophages and neutrophils). NO acts on platelets to inhibit platelets adhesion and aggregation. NO causes relaxation of the smooth muscle of the cavernosal blood vessels of the penis, leading to vasodilation, tumescence and stimulation. Release of NO in the corpus cavernosum of the penis during stimulation activates the enzyme guanylate cyclase, which results in increased levels of cGMP, producing smooth muscle relaxation in the corpus cavernosum and resulting in increased blood flow (5). NO is mainly produced from cavernosal nerves, which are nonadrenergic, noncholinergic nerves within the penis, and acting via its second messenger cGMP. It has been suggested that maintaining normal body weight and mild exercise, as well as dietary supplementation of folic acid, zinc, calcium, vitamin C, vitamin E and L-arginine, a precursor of NO, can support the biochemical pathway leading to NO release [6]. NO is an effector molecule that is involved in a number of intracellular functions such as vasorelaxation, endothelial regeneration, inhibition of leukocyte chemotaxis and platelet adhesion [7]. A small proportion of autonomic nerves do not release either Ach or norepinephrine [8]. For example, the cavernous nerves predominantly release NO in the penis. The exact mechanism is not known, but it is believed to be through increased intracellular calcium. Another gaseous molecule produced in the corpora cavernosa is hydrogen sulphide (H2S), which is also known to be involved in erectile function [9]. H2S activates ATP-sensitive potassium channels in smooth muscle cells. Some reports indicate that NO acts in large vessels and H2S in small vessels. A high level of tumour necrosis factor-alpha has been shown in ED patients [10]. Although current ED therapies using PDE-5 inhibitors are safe and effective, approximately 40% of ED patients do not respond to currently available treatment [11,12]. For these patients, herbal therapy may be useful.
"Ikawe has really boosted my sex drive as you said it would! My wife used to complain that I was never interested. She said her friends always complained that their husbands wanted too much sex but she hardly got any. Seriously - it was affecting my marriage. After taking Ikawe for 10 days I could already feel the difference. I also have much more energy." - Derrick S., USA
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.
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