NITRIC OXIDE SUPPLEMENTS? DO THEY WORK?

SUMMARY OF NITRIC OXIDE SUPPLEMENTS

• Nitric oxide supplements should not be taken with caffeine

• L-Arginine products should not be used. Limited studies show arginine can increase blood flow.

• L-Cirulline and Beetroot were the two products that have been found to improve performance, although not all studies found positive effects.

“Mind-blowing pumps!” “Skin-tearing pumps!” These are the benefits of nitric oxide supplements typically found on the front of most nitric oxide supplements. Pre-workout supplements that contain nitric oxide boosters usually contain a combination of arginine and l-citrulline branched-chain amino acids, beta-alanine, and creatine to support increasing oxygen and nutrients to the muscle.

Nitric oxide (NO) is a gaseous molecule that regulates blood flow, muscle contractility, and mitochondrial function. (Campos et al., 2018) NO opens up blood vessels to enhance muscles with oxygen and nutrients.

PRE-WORKOUT INGREDIENTS TO INCREASE NITRIC OXIDE AND MUSCLE GROWTH

The two precursors for NO production include the amino acid L-arginine and nitrates foods in foods, with L-citrulline serving as a precursor to L-arginine.

NO does more than just enhance blood flow; researchers have found that increased NO contributes to increases in protein synthesis, muscle growth, and training adaptations. (Schoenfeld & Contreras, 2014). For example, one study found a relationship between post-exercise muscle pumps and muscle growth. (Hirono et al., 2022)

WHAT INGREDIENTS GIVE YOU A PUMP?

Most bodybuilders will combine a nitric oxide supplement with a high-repetition muscle pump workout. A new review in the journal Nutrients released a comprehensive review of the ingredients in popular pump formula pre-workouts and their effects on performance. (Gonzalez et al., 2023) Here is the summary of evidence provided by the authors:

L-Arginine:

L-arginine is commonly found in foods such as meat, seafood, nuts, seeds, watermelon, and soy. (Bescós et al., 2012) Arginine was a popular product in the early 2000s to increase GH, but few studies validate it. Massive dosages of L-arginine are needed as there are few benefits to acutely increasing anabolic hormones for muscle growth.

Even though many erectile dysfunction ED supplements advocate arginine for better sex, supplementing with 6–10 grams of arginine does not affect NO production, blood flow to muscle tissue, muscle protein synthesis, or strength performance. (Fahs et al., 2009; Tang et al., 2011)

Most studies have found that L-arginine does not increase performance, and the authors recommended not using arginine.

Citrulline and Citrulline Malate:

L-citrulline serves as a pre-cursor for L-arginine. L-citrulline is an indirect NO precursor; studies have found that L-citrulline supplementation increases L-arginine levels more than L-arginine supplementation. (Schwedhelm et al., 2008) L-citrulline is preferable to L-arginine as large dosages of L-arginine have poor bioavailability.

The research on L-citrulline and L-citrulline malate are inconclusive for performance enhancement. Some studies show performance increases, and others show no effect. Of the 16 studies analyzed, only 5 showed performance improvements.

Most of the studies have not shown L-citrulline to enhance muscle blood flow. Studies have found that citrulline does not increase muscle growth. (Gonzalez et al., 2018; Hwang et al., 2018)

A minimum dose of 3 grams of L-citrulline is needed for performance enhancement, but studies have used up to 15 grams. One study found that 8 grams of citrulline malate improved repetitions to failure. (Gough et al., 2021)

Nitrate Supplements (i.e., beetroot juice):

Nitrates are converted to nitric oxide.  Foods rich in dietary nitrates are leafy green vegetables, spinach, arugula, and beets. Most people don’t know this, but you can store nitrates in the muscle like glycogen. (Nyakayiru et al., 2020)

Beetroot juice has been found to reduce high blood pressure, improve anti-oxidant activity, and reduce the negative vascular effects of sitting for extended periods.(Gamonales et al., 2022; Morishima et al., 2022)

The most common supplement to increase nitrates is beetroot juice which usually occurs 2-3 hours after consumption. Beetroot juice is well-documented to increase vasodilation and blood flow.

The research on beetroot juice supplementation is mixed, but most studies show a favorable response to endurance and resistance exercise programs. Of the 18 studies examined, only three found no effect.

The authors recommended 400 mg or 6.4 mmol of beetroot juice for resistance exercise improvements.