What Is L-Arginine?

L-arginine is an amino acid that your body naturally produces to make protein. It is also thought to improve circulation and immunity. Available in oral and topical supplement forms, it is also L-arginine is also found in some plant and animal proteins, including fish, soy, nuts, whole grains, and dairy products.

L-arginine also helps rid the body of ammonia (a waste product) and stimulates the release of insulin. In addition, your body uses arginine to make nitric oxide (a compound that relaxes the blood vessels).

Although some studies suggest that L-arginine may benefit certain health conditions, other research shows that L-arginine may have harmful effects on some individuals.

What Is L-Arginine Used For?

By improving blood flow in the body, some proponents claim that L-arginine may help heart conditions, such as chest pain (angina), high blood pressure, leg cramping and weakness due to obstructed arteries (a condition known as intermittent claudication), and erectile dysfunction (ED).

Some people use L-arginine to boost the immune system, improve athletic performance, shorten recovery time after surgery, and promote weight loss. L-arginine is also used for bodybuilding.

There's also some evidence that L-arginine may help with interstitial cystitis and preeclampsia.

At this point, there are few clinical trials testing the potential benefits of L-arginine. Here's a look at a few findings from the available research:

Erectile Dysfunction

Some research has examined whether L-arginine supplements may benefit men with erectile dysfunction, also known as ED. L-arginine is thought to enhance nitric oxide and—in turn—relax the muscles surrounding blood vessels supplying the penis. As a result, blood vessels in the penis dilate, increasing blood flow, which may help maintain an erection.

In a 2017 study published in the journal Andrology, for instance, levels of L-arginine and L-citrulline (another amino acid) were measured in people with erectile dysfunction. Researchers found that levels of both amino acids were lower in men with erectile dysfunction than in those without ED.

A couple of small studies have explored the use of L-arginine in combination with French maritime pine bark extract (Pycnogenol®).

Heart Disease

Early proponents suggested that L-arginine could protect the heart and benefit people with heart disease, however, a study published in the Journal of the American Medical Association in 2006 found that arginine didn't improve blood vessel stiffness or heart function in people 60 years or older who took arginine in combination with standard treatment after a heart attack. What's more, the researchers found that "arginine may be associated with higher postinfarction mortality."

Further research published in 2016 suggests that arginine supplementation could raise the risk of heart disease. Until we know more, L-arginine supplements cannot be recommended as a treatment for heart disease.

Nutrition Therapy

Taking L-arginine in combination with an omega-3 fatty acid and nucleotides have been explored to reduce recovery time, protect against infection, and promote wound healing after surgery. The supplement in combination with other supplements has also been used to increase lean body mass in people with cancer.

Possible Side Effects

L-arginine can cause a number of side effects including indigestion, nausea, headache, bloating, diarrhea, gout, blood abnormalities, allergies, airway inflammation, worsening of asthma symptoms, decreased insulin sensitivity, and low blood pressure.

Higher doses of L-arginine can increase stomach acid, so it may also worsen heartburn, ulcers, or digestive upset caused by medications. In addition, L-arginine may aggravate symptoms in people with herpes.

L-arginine may interact with certain medications, such as blood pressure medication, diabetes medication, or drugs used to treat erectile dysfunction. If you have diabetes or heart disease, avoid taking L-arginine. Some studies have found that chronic L-arginine supplementation may decrease insulin sensitivity, while others have found no effect or increased insulin sensitivity.

As with many other supplements, L-arginine hasn't been tested for safety in pregnant women, nursing mothers, children, and those with medical conditions or who are taking medications.

Dosage and Preparation

There is no standard recommended dose of L-arginine. The appropriate dose for you may depend on factors including your age, gender, and medical history.

Various doses of L-arginine have been studied in research investigating its effect on different conditions. For example, for chest pain, a dose of 2-6 grams three times per day for up to one month has been used. For erectile dysfunction, a dose of five grams per day has been used. And in studies investigating high blood pressure, a dose of 4-24 grams per day for 2-24 weeks has been used.

Speak to your healthcare provider to get personalized advice.

Diet and Interactions

In most cases, the body maintains an adequate supply of L-arginine on its own. However, severe burns, infections, and injuries can deplete the body's supply of arginine. Under these conditions, it is necessary to ensure proper intake to meet the increased demands.

L-arginine is found in foods that you consume, including red meat, poultry, fish, lentils, and dairy products. Consider adding more chicken, turkey, lean cuts of beef, soybeans, pumpkin seeds, peanuts, lentils, lobster, shrimp, spinach or seaweed to your diet.

Due to evolving research on the relationship between L-arginine and heart disease, avoid taking L-arginine supplements unless you have consulted your healthcare provider first about the possible benefits and risks.