There’s no shortage of supplements marketed for weight loss, but many are ineffective and some are downright dangerous. It can be hard to separate the sales-speak from the science. That’s where we come in.

L-arginine is a natural compound that’s sometimes sold as a weight loss supplement. We’re diving into the research behind this supp to see if it works (and whether it’s safe).

What is L-arginine?

L-arginine is an amino acid, one of the building blocks of proteins. L-arginine is considered a semi-essential (aka conditionally essential) amino acid. This means your body can make it, but you might need to get more from your diet in some cases.

For example, L-arginine needs are much higher during infancy, pregnancy, critical illness, and serious injuries. Your bod uses L-arginine for lots of important functions, including blood flow regulation, immune function, and the creation of other powerful amino acids, such as glutamate and creatine.

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Research suggests that L-arginine supplements could benefit health in a number of ways. But there isn’t much scientific proof that L-arginine supports weight loss. Here’s what the research says:

  • A few studies have found that taking high doses of L-arginine may help reduce waist circumference, but it doesn’t seem to improve weight loss or body mass index (BMI).
  • Even though findings from older studies suggest that L-arginine may enhance fat loss, more recent studies haven’t confirmed this.
  • A 2017 study in male soccer players found that supplementing with 2 grams of L-arginine per day for 45 days didn’t affect body fat or BMI.

TL;DR: According to current research findings, L-arginine doesn’t seem to promote fat loss or weight loss in general.

Other (better) ways to lose weight

If you’re trying to lose weight, it’s best not to depend on supplements.

Instead, you can try making some dietary changes like increasing your intake of whole-food sources of fiber, protein, and healthy fats and decreasing your intake of highly processed foods and added sugar. You can also try increasing your daily activity level.

Getting help from a qualified healthcare professional, such as a registered dietitian, can also be helpful when you’re trying to reach and maintain a healthy body weight.

Even though L-arginine doesn’t seem to be effective for weight loss, it has been associated with a few other health benefits.

May improve athletic performance

One of the most studied benefits of L-arginine is its ability to enhance athletic performance.

A 2020 review of 15 studies found that L-arginine supplements were effective for improving both aerobic and anaerobic performance tests. The researchers were able to narrow down the best doses for various timelines and goals:

  • Short-term: 0.07 grams per pound of body weight, taken 60 to 90 minutes before a workout
  • Long-term (for aerobic performance): 1.5 to 2 grams per day for 4 to 7 weeks
  • Long-term (for anaerobic performance): 10 to 12 grams per day for 8 weeks

Could help lower blood pressure

L-arginine is necessary for the production of nitric oxide, a signaling molecule that’s involved in blood pressure regulation.

Several research reviews have found that L-arginine supplements and intravenous (IV) L-arginine treatments are effective for reducing blood pressure in people with high blood pressure.

Other potential benefits

Some study findings suggest that L-arginine may help improve blood sugar regulation in people with diabetes and may even delay the development of type 2 diabetes in people at a high risk of developing this medical condition.

L-arginine is also used to treat serious infection and trauma in clinical settings. For example, high dose IV L-arginine is sometimes used to treat patients with burns, serious infections, and injuries.

Additionally, high dose L-arginine supplements may offer benefits for those experiencing erectile dysfunction, immune health, or preeclampsia, a serious condition that can occur during pregnancy.

L-arginine is considered safe, even when it’s taken at high doses for long periods of time.

However, research suggests that taking 9 grams or more of L-arginine per day is more likely to result in gastrointestinal side effects like diarrhea, nausea, bloating, and abdominal pain.

L-arginine could also interact with certain medications, including those used to treat high blood pressure and high blood sugar.

If you’re interested in taking L-arginine, consult a healthcare professional first. They can help you determine whether L-arginine fits your health needs and goals and whether it interacts with any natural supplements you’re taking. Since supplements aren’t regulated in the same way as food and medicine, your doctor can also help you find a trusted product that’s right for you.

Who shouldn’t take L-arginine?

Even though L-arginine is safe for most people, certain populations should avoid these supplements, including those who:

  • have had a heart attack recently
  • have kidney disease
  • have guanidinoacetate methyltransferase deficiency, an inherited disorder that affects arginine metabolism
  • are undergoing surgery within 2 weeks

If you’re hoping to lose body fat, popping an L-arginine supplement isn’t likely to help you reach that goal.

While L-arginine offers other benefits, such as improving athletic performance and decreasing high blood pressure levels, it doesn’t seem to be effective for enhancing weight loss.

If you want to lose weight, you can try evidence-based methods like eating more fiber- and protein-rich foods and being a bit more active each day.