Nitric Oxide: A Versatile Molecule in the Body

Nitric oxide (NO) is a small gaseous molecule involved in intercellular communication and signals in many physiological processes. A systematic review describes NO's vasodilatory effect with measurements of decreased blood pressure and increased delivery of oxygen and nutrients to organs (PMID 32292042). The same review notes that beet juice, rich in nitrates, has become popular among athletes for this reason.

NO measurements are also used in inflammation research. An analysis compiling studies on the RAW 264.7 cell model stimulated with lipopolysaccharide (LPS) reported that measuring NO alongside inflammatory biomarkers such as TNF-alpha, IL-1beta, and IL-6 can be used to screen for potential anti-inflammatory effects (PMID 35612604). Such in vitro models define a screening step, not a treatment outcome.

In exercise research, food sources that enhance NO bioavailability are a separate topic. A meta-analysis compiling 118 studies reported minor but statistically significant effects on endurance performance in foods rich in nitrates and polyphenols (SMD 0.15 and 0.17, respectively), but no effect was reported for L-citrulline sources (PMID 34965876). The same analysis noted no significant effect in female participants and that nitrate sources did not show benefits in well-trained athletes.

The same systematic review reports that questions about dosage and safety remain open with high nitrate intake (PMID 32292042).

The studies compiled in this section examine NO bioavailability alongside cardiovascular measurements and endurance outcomes; the reported effect sizes vary across studies (PMID 32292042, PMID 28067808, PMID 34965876).

Nitric oxide carries a relaxation signal to vascular smooth muscle; this is a defined physiological node in the regulation of blood flow. A systematic review conveys this effect with measurements of decreased blood pressure and increased delivery of oxygen and nutrients to organs (PMID 32292042). These features explain why the NO pathway is a subject of investigation in cardiovascular research; the compiled sources here are not presented as a prevention or treatment outcome.

NO production occurs primarily through nitric oxide synthase (NOS) enzymes. A systematic review and meta-analysis examining the Glu298Asp polymorphism in the NOS3 gene associated this variant with low circulating nitric oxide levels and the risk of coronary artery disease (PMID 37451608). The same analysis notes that the relationship is particularly reported for individuals of non-European descent for acute coronary syndrome or early coronary artery disease.

A systematic review of 23 studies examining beetroot juice supplementation reported increased efficiency in cardiorespiratory endurance measurements and prolonged time to exhaustion at submaximal intensities (PMID 28067808).

L-arginine is an amino acid precursor to NO. A systematic review of L-arginine supplementation during pregnancy reported reductions in blood pressure measurements and improvements in fetoplacental circulation indicators in participants with hypertensive pregnancy disorders (PMID 37258415).

In asthma research, nitric oxide is monitored as FeNO measured in exhaled air. FeNO is an indirect indicator of type 2 inflammation in the airways. A patient-level meta-analysis compiling 6,513 participants from control groups of 22 randomized studies associated a tenfold increase in FeNO with a 1.44-fold increase in attack risk (PMID 40215991). Another meta-analysis reports FeNO measurements among the outcomes observed post-intervention in participants with asthma (PMID 37073761).

These findings demonstrate that NO is studied both as a signaling molecule and a measurement tool. The same literature also records the potential risks of high nitrate intake (PMID 32292042).

Beetroot juice is known for its high nitrate content, and a portion of these nitrates convert to nitric oxide in the body after consumption. A systematic review reports this process alongside measurements of decreased blood pressure and increased delivery of oxygen and nutrients to organs (PMID 32292042). Studies measuring oxygen delivery to muscles are cited as reasons for its popularity among athletes.

The same review also records the risk aspect: nitrate intake exceeding the acceptable daily intake can trigger the endogenous formation of N-nitroso compounds, which are known carcinogens (PMID 32292042). The review notes that the data pool on adverse effects is limited compared to positive effects.

A systematic review compiling L-arginine supplementation during pregnancy reported reductions in blood pressure measurements and improvements in fetoplacental circulation indicators among participants with hypertensive pregnancy disorders (PMID 37258415).

In the context of asthma, nitric oxide is used as a marker of inflammation. A patient-level meta-analysis compiling control groups from 22 randomized studies associated high FeNO and high blood eosinophil counts with an increased risk of attacks (PMID 40215991). These measurements are referenced in discussions of clinical risk classification; this page does not provide a clinical decision recommendation.

On the exercise front, a meta-analysis compiling food sources rich in nitrates and polyphenols reported statistically significant but minor effects on endurance performance (PMID 34965876). The same analysis notes that effects vary according to the type of food and participant characteristics.

These studies demonstrate the outcomes with which NO production and bioavailability are measured. The common note of the reviews is that more research is needed to fully understand the effects.

Beetroot juice, known for its high nitrate content, is frequently studied in endurance research (PMID 32292042). Systematic reviews evaluate nitrate-rich food sources in conjunction with cardiorespiratory endurance measurements and time to exhaustion at submaximal intensity (PMID 28067808, PMID 34965876); the reported effects are small and vary by food type.

Nitric oxide measurement is also used as a screening step in inflammation research (PMID 35612604). In asthma research, FeNO is a marker examined for its relationship with attack risk (PMID 40215991).

The same literature reports potential risks of high nitrate intake (PMID 32292042). This page does not contain usage recommendations, product guidance, or dosage schemes; individual dietary decisions are made within the framework of medical advice and food regulations.

This section contains brief notes on the scope of studies mentioned in the body; the page's source list is also printed in the bibliography section.

Beetroot juice reviews examine nitrate intake conversion to nitric oxide, blood pressure measurements, and endurance endpoints; the same reviews also record potential risks of high intake (PMID 32292042, PMID 28067808).

In inflammation research, NO is a screening marker measured alongside TNF-alpha, IL-1beta, and IL-6 in the LPS-stimulated RAW 264.7 cell model (PMID 35612604).

On the respiratory side, FeNO is among the endpoints monitored in asthma intervention studies (PMID 37073761), and in a patient-level meta-analysis of 22 randomized trials with control groups, it was associated with attack risk among 6,513 participants (PMID 40215991).

On the genetic side, the Glu298Asp variant in the NOS3 gene has been examined in relation to circulating NO levels and coronary artery disease risk (PMID 37451608).

During pregnancy, L-arginine supplementation has been reviewed alongside blood pressure and fetoplacental circulation indicators (PMID 37258415).