L-lysine is one of those supplements that people take without much concern. It’s a naturally occurring amino acid that your body needs to make protein. L-lysine may be helpful in preventing or treating a number of health concerns, such as herpes-simplex infections, anxiety, and high blood sugar.

Lately, there have been reports that not getting enough L-lysine can cause erectile dysfunction (ED). But is there any truth to this?

ED is the inability to get an erection or maintain an erection long enough for sexual intercourse.

Erections occur when nitric oxide triggers a chemical process in which the arteries of the penis widen, enabling them to quickly fill with blood. When a man experiences ED, an enzyme interferes with dilation of the arteries in the penis.

ED is extremely common, about 40 percent of 40-year-old men get ED. By the time men reach age 70, that number climbs to 70 percent.

ED can be caused by a number of things. The most common are:

  • heart and vascular diseases
  • diabetes
  • prostate disease
  • obesity
  • depression
  • substance abuse
  • some medications, including medications used to treat blood pressure and depression

Somewhere between 17 and 20 percent of your body consists of proteins. Proteins are made of strings of amino acids. Amino acids are key to growing and repairing cells throughout your body. They form antibodies that protect you and enzymes that are part of many processes that make your body function.

L-lysine, or lysine, is one of nine essential amino acids, meaning your body requires it but cannot produce it. Instead, lysine must come from food or supplements.

No credible research supports the notion that lysine deficiency causes ED. A number of men’s health publications and nutritional supplement manufacturers make claims about lysine, such as:

  • A lack of lysine can cause impotence.
  • L-lysine has been known to help create firmer erections.
  • L-lysine can enhance penis volume.

As promising as these claims are, they’re not backed up by research.

Although low levels of lysine don’t cause ED, lysine may have a small role in reducing the incidence or severity of the condition.

Plaque buildup in penile arteries

L-lysine taken in combination with vitamin C may help reduce levels of lipoprotein-a (LPA). LPAs carry cholesterol in the blood and contribute to the buildup of plaques that can clog your arteries. If your LPA levels are high, you’re at risk for heart disease, stroke, and ED.

According to Mayo Clinic, smaller arteries, such as the arteries in a penis, are the first to become clogged. And when the arteries of your penis are clogged, the blood flow necessary for an erection is blocked.


As most men know, anxiety is no help when you have ED. For some men, anxiety is a total game changer. A research review published in Nutrition Journal cited two studies in which L-lysine combined with L-arginine reduced anxiety in study participants. The review’s authors note that further studies are needed to confirm the effectiveness of these supplements.

If you have erectile dysfunction, there are a number of medication and surgical options for treating the condition. Your best bet? Speak with your doctor about those options before trying supplements.