The Potential Benefits of Combining L-Arginine and L-Citrulline Supplements

If you have health issues, talk to your doctor before supplementing with L-arginine and L-citrulline.
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If you've heard about the amino acids L-arginine and L-citrulline, you may be wondering about their health benefits — and if you should take them together. The short answer is maybe. Here's why.

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Better Together: L-Arginine and L-Citrulline

"Both L-arginine and L-citrulline are important amino acids that our bodies need to function properly," says New York-based Monica Salinas, RD, CDN, a critical care dietitian at Montefiore Medical Center.

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"Citrulline is converted into arginine in the body. That is why it is believed to help increase arginine levels, and the reason why sometimes both may be taken together," Salinas says.

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But there's limited research currently backing this practice. A small February 2019 study in ‌European Journal of Applied Physiology‌ examined the effects of 1.2 grams per day of each L-arginine and L-citrulline supplements on the performance of 24 players on a men's college soccer team. After seven days of taking both amino acids, the athletes had improved performance and perceived output on a 10-minute cycling test.

A September 2019 article in ‌Advances in Nutrition‌ also implies there are benefits of taking the two compounds together if you're pregnant: L-arginine and L-citrulline were associated with improved birth outcomes such as higher birth weight and longer gestation.

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L-Arginine Benefits

Taken separately, these amino acids also have individual benefits. L-arginine helps your body build protein and is a vasodilator, meaning it opens blood vessels — making oral supplementation a potential support for health issues like erectile dysfunction and some heart conditions, per the Mayo Clinic. In fact, research has linked it with improvements in:

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Before you run out and buy it, keep in mind results are mixed, Salinas says. "Some studies have shown arginine can have some vascular benefits and help lower blood pressure, decrease symptoms of angina or help with blood glucose control, but check with your doctor if you qualify to begin supplementation."

Also, though L-arginine is considered to be generally safe, it is not without potential side effects, according to the Mayo Clinic. L-arginine can interfere with some medications (like those for blood pressure, diabetes and more), so always check with your doctor before giving it a try.

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L-Citrulline Benefits

L-citrulline is not removed from the body in large quantities, so it more effectively increases L-arginine levels and nitric oxide synthesis, which promotes heart health, according to a July 2018 review in Nutrients.

The ‌Nutrients‌ review also found L-citrulline and watermelon extract supplementation (L-citrulline comes from the Latin word for watermelon: ‌citrullus‌) was linked to lower blood pressure and improved muscular and metabolic health in older adults.

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These findings, alongside a low adverse effects profile, make L-citrulline an appealing option to support healthy aging, per the review, though more research is needed to fully understand the benefits and uses of this amino acid.

More Research-Backed Ways to Support Your Heart Health

While there is some promising preliminary research, Salinas says more studies are needed before she can make a specific recommendation to take either supplement.

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Salinas says a lot of unanswered questions about the supplements remain, noting no specific recommended daily allowance has been set: "I do not recommend supplementation for the general population since our bodies produce enough," Salinas says.

"You can obtain the cardiovascular health benefits believed to be obtained from arginine supplementation by maintaining a healthy weight and following a heart-healthy diet," she says, which includes:

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"Of course, it also helps to be physically active," Salinas says.

And if you have interest in taking L-arginine and L-citrulline for blood pressure or other health concerns, Salinas says you should speak with your doctor first.

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