Short-Term L-Citrulline Supplementation Does Not Affect Inspiratory Muscle Oxygenation and Respiratory Performance in Older Adults.

2023-04-18
Nutrients 15(8)
- Anastasios A Theodorou
- Panagiotis N Chatzinikolaou
- Nikos V Margaritelis
- Filippos Christodoulou
- Themistoklis Tsatalas
- Vassilis Paschalis

PubMed: 37111169
DOI: 10.3390/nu15081951

Study Design

Type: Randomized Controlled Trial (RCT)
Population: Fourteen healthy older males
Methods: 6 g of L-citrulline or a placebo for seven days in a double-blind crossover design
Blinding: Double-blind
Duration: seven days
Funding: Unclear

Rigorous Journal

In sports nutrition, nitric oxide (NO^•) precursors such as L-citrulline are widely used to enhance NO^• bioavailability, which is considered an ergogenic aid. Our study aimed to examine the effect of short-term L-citrulline supplementation on respiratory muscles' performance, fatigue, and oxygenation in older adults. Fourteen healthy older males took 6 g of L-citrulline or a placebo for seven days in a double-blind crossover design. Pulmonary function via spirometry (i.e., forced expired volume in 1 s (FEV₁), forced vital capacity (FVC), and their ratio)), fractional exhaled nitric oxide (NO^•), maximal inspiratory pressure (MIP), rate of perceived exertion, and sternocleidomastoid muscle oxygenation (i.e., oxyhemoglobin (Δ[O₂Hb]) and de-oxyhemoglobin (Δ[HHb]), total hemoglobin concentration (Δ[tHb]), and tissue saturation index (TSI%)) were evaluated at baseline, after seven days of L-citrulline supplementation, and after incremental resistive breathing to task failure of the respiratory muscles. The exhaled NO^• value was only significantly increased after the supplementation (26% p < 0.001) in the L-citrulline condition. Pulmonary function, MIP, rate of perceived exertion, and sternocleidomastoid muscle oxygenation were not affected by the L-citrulline supplementation. In the present study, although short-term L-citrulline supplementation increased exhaled NO^•, no ergogenic aids were found on the examined parameters at rest and after resistive breathing to task failure in older adults.

Research Insights

L-Citrulline→Improved FEV1/FVC Ratio
Pulmonary function, MIP, rate of perceived exertion, and sternocleidomastoid muscle oxygenation were not affected by the L-citrulline supplementation.
Effect
Neutral
Effect size
Small
Dose
6 g/day
L-Citrulline→Improved Forced Expiratory Volume in One Second
Pulmonary function, MIP, rate of perceived exertion, and sternocleidomastoid muscle oxygenation were not affected by the L-citrulline supplementation.
Effect
Neutral
Effect size
Small
Dose
6 g/day
L-Citrulline→Improved Forced Vital Capacity
Pulmonary function, MIP, rate of perceived exertion, and sternocleidomastoid muscle oxygenation were not affected by the L-citrulline supplementation.
Effect
Neutral
Effect size
Small
Dose
6 g/day
L-Citrulline→Improved Maximal Inspiratory Pressure
Pulmonary function, MIP, rate of perceived exertion, and sternocleidomastoid muscle oxygenation were not affected by the L-citrulline supplementation.
Effect
Neutral
Effect size
Small
Dose
6 g/day
L-Citrulline→Improved Tissue Saturation Index
Pulmonary function, MIP, rate of perceived exertion, and sternocleidomastoid muscle oxygenation were not affected by the L-citrulline supplementation.
Effect
Neutral
Effect size
Small
Dose
6 g/day
L-Citrulline→Increased Exhaled Nitric Oxide Level
The exhaled NO• value was only significantly increased after the supplementation (26% p < 0.001) in the L-citrulline condition.
Effect
Beneficial
Effect size
Moderate
Dose
6 g/day
L-Citrulline→Increased Hemoglobin Levels
Pulmonary function, MIP, rate of perceived exertion, and sternocleidomastoid muscle oxygenation were not affected by the L-citrulline supplementation.
Effect
Neutral
Effect size
Small
Dose
6 g/day
L-Citrulline→Increased Oxyhemoglobin Level
Pulmonary function, MIP, rate of perceived exertion, and sternocleidomastoid muscle oxygenation were not affected by the L-citrulline supplementation.
Effect
Neutral
Effect size
Small
Dose
6 g/day
L-Citrulline→Reduced Perceived Exertion
Pulmonary function, MIP, rate of perceived exertion, and sternocleidomastoid muscle oxygenation were not affected by the L-citrulline supplementation.
Effect
Neutral
Effect size
Small
Dose
6 g/day