L-arginine (el-AHR-jih-nene) is an organic substance called an amino acid. Your body usually makes all the L-arginine it needs. You also get L-arginine through your diet in foods such as nuts, fish, red meat, soy, whole grains, beans and dairy products.

The body changes L-arginine to nitric oxide, a substance known to widen blood vessels. Some people take L-arginine supplements to relax and open arteries, which might help lower blood pressure. However, L-arginine supplements are rarely necessary and may only benefit people who have a true deficiency.

Research on L-arginine has had mixed results. The most recent research suggests that L-arginine may lower blood pressure, improve cholesterol and improve overall blood vessel health.

A review of several studies found that adults with high blood pressure who took daily L-arginine supplements lowered their bottom (diastolic) blood pressure number by about 2 to 3 millimeters of mercury (mm Hg).

When it comes to heart health, L-arginine may work better when combined with other vitamins, such as vitamins B6 and B12. However, larger, more-robust studies are needed to confirm these findings before experts can recommend everyday use of these supplements.

L-arginine drug interactions

It's important to know that L-arginine supplements can interact with some medications, including:

• Blood thinners, including aspirin and warfarin
• Certain diuretics
• Nitroglycerin
• Some high blood pressure medications
• Erectile dysfunction drugs
• Diabetes medications

Who shouldn't take L-arginine

Don't take L-arginine if you've had a heart attack. There are concerns that the supplement might increase the risk of death.

L-arginine supplements can worsen allergies and asthma. Use with caution.

Don't take L-arginine supplements if you've had cold sores or genital herpes. Too much L-arginine in your system can activate the virus that causes those conditions.

Talk to your doctor about supplements

A healthy diet and regular exercise are among the best ways to keep your blood pressure healthy. If you're thinking about taking an herbal or dietary supplement, such as L-arginine, talk to your doctor first. Some supplements can interact with blood pressure medications or make certain health conditions worse.