The evidence
What this body part actually runs on.
Four tiers, in plain language: what has trial evidence, what has weak evidence, what has none, and what is sold anyway because the buyer is too embarrassed to check. Read the fourth one before you order from anyone, including us.
The mechanism
It is a plumbing problem with a nervous system attached.
An erection is blood entering and staying in. The signal is nitric oxide released from the endothelium, the cell layer lining your blood vessels. Nitric oxide raises cyclic GMP, cGMP relaxes the smooth muscle in the arteries feeding the penis, and blood fills the tissue. The vein that drains it is compressed as pressure rises, which is what holds it there.
Everything that damages the endothelium damages this. High blood pressure, high blood sugar, smoking, sleep apnea, a sedentary year, chronic stress, and ageing. That is why the same man who has an erection problem often has a blood pressure problem, and why the two are treated by the same set of habits.
The practical consequence: anything that only addresses "drive" while ignoring the vessels is treating the wrong organ. And anything promising permanent structural size change is not treating any organ at all.
Tier one
Has trial evidence.
These are the interventions with randomised data and a mechanism that matches it. If you do nothing else, do these.
PDE5 inhibitors
Sildenafil and tadalafil. Decades of trials, predictable onset, known interactions. The only thing in this category that works on demand, and it requires a prescription for good reason.
Aerobic training
Zone two cardio, three sessions a week, for eight weeks or more. Trials show measurable improvement in erectile function, comparable in some studies to a moderate drug effect.
Treating sleep apnea
Untreated apnea fragments deep sleep and drops oxygen. Men with apnea have markedly higher rates of erectile dysfunction, and treatment improves it. This is the most under diagnosed cause on the list.
Pelvic floor training
Supervised pelvic floor muscle training has trial support for erectile function, not just incontinence. It is free, unglamorous and rarely mentioned by anyone selling a bottle.
Treating performance anxiety
CBT has good evidence, and anxiety driven failure is self reinforcing. A bad night creates the fear that causes the next one. This is a treatment, not a mindset slogan.
Testosterone, if it is low
Only if measured low, twice, in the morning, with symptoms. Replacement helps those men. It is not a performance enhancer for men with normal levels, whatever the clinic advertises.
Tier two
Has weak or mixed evidence.
Plausible mechanism, small studies, inconsistent results. We sell some of these, at honest doses, described as adjunct rather than cure. This is the tier where most of the supplement industry pretends to be tier one.
| Compound | What the data shows | Our position |
|---|---|---|
| L-citrulline | Raises plasma arginine and improves flow mediated dilation. Sexual function data is small but consistent in direction. | Sold, at 3 g, as the mechanism base. |
| Dietary nitrate | Beetroot juice improves vascular measures. Sexual outcome data is thin. | Sold as part of the nitrate blend. |
| Pine bark extract | One small trial showed benefit in men with mild dysfunction. Not replicated at scale. | Not sold. One trial is not enough for a price tag. |
| Ashwagandha | Modest cortisol and stress effects. Some small testosterone signals in stressed or overweight men. | Sold, for sleep and stress, not as a testosterone claim. |
| Zinc and vitamin D | Correcting a deficiency helps. Supplementing when replete does very little. | Sold as a foundation, with a test-first instruction. |
Tier three
Has no evidence, and is sold anyway.
This is the part of the market that funds the billboards. Every item below is legal to sell, easy to find, and unsupported by anything resembling a trial.
Permanent size from a pill
Nothing oral changes the structure of the tissue. Sellers of this claim have paid eight figure settlements in the United States, repeatedly, for two decades.
Pumps and stretchers for growth
A pump produces temporary engorgement. Traction devices have small, low quality studies and a real injury rate. Neither is a plan, and the marketing is written for men in distress.
"Test boosters"
Tribulus, fenugreek blends, deer antler. Sold on the word testosterone, studied almost never, dosed to look good in a capsule rather than in a blood test.
Volume injections from unlicensed providers
Permanent filler in this tissue has caused deformity, migration and necrosis. The complication is not rare and it is not reversible.
Tier four
Unapproved injectables, including exosomes.
Exosomes are small vesicles cells release. As a research object they are genuinely interesting. As a consumer injectable for sexual function, they are an unapproved drug with no batch oversight, and the FDA has issued public safety notifications after patients were seriously harmed by products marketed this way. There are no approved exosome products for human use.
The commercial pattern is consistent. A vial is labelled research use only, then the storefront, the email and the influencer all describe injecting it. That label is not a shield. Selling a product you market for injection, without approval, is selling a drug.
We are not going to sell it, ship it, affiliate it or write around it. If a supplier offers you a "sexual health exosome protocol" with a consent form, the consent form is protecting them.
Checklist
Seven things to fix before you buy anything from anyone.
Ordered by cost, cheapest first. Most men who work through this list do not need the fourth item on it.
Sleep seven hours
Consistently, same window. This is where most of your testosterone is made.
Train the heart
Zone two, three times a week. The penis is a vascular organ, and the training effect is systemic.
Get a blood pressure reading
Free at most pharmacies. High blood pressure is the most common treatable cause nobody checks.
Get tested, not guessed
Vitamin D, testosterone in the morning, HbA1c, lipids. Four numbers beat any supplement decision.
Cut the alcohol load
Two drinks does more vascular damage than most men want to hear. It is also the easiest variable to move.
Ask about apnea
Snoring, waking unrefreshed, daytime sleepiness. If yes, get a sleep study before you buy a bottle.
Then a clinician
If it is still a problem, a prescription will outperform every supplement on this page. That is what the review page is for.