L-Citrulline for Fertility and Reproductive Health

L-Citrulline – A Powerful Amino Acid for Fertility

The amino acid called citrulline, or “L-citrulline,” in its supplemental form, is derived from foods such as watermelon, cucumber, and pumpkin. Although it’s been researched since the late 19th century, it wasn’t until 1914 that two Japanese researchers isolated the amino acid. L-citrulline is considered one of the most important amino acids, molecules that form proteins and serve as the body’s energy source. While amino acids generally produce protein, L-citrulline isn't used for this purpose, although it may help boost other chemicals needed to make protein. 

L-citrulline possesses the properties of an antioxidant, a nutrient offering protection against oxidative damage, which accumulates due to higher levels of unstable molecules, called free radicals or reactive oxygen species (ROS). Although beneficial for various processes, like ovulation and insulin utilization, ROS molecules cause damage to DNA and cell membranes. They also cause oxidative stress and inflammation, associated with diabetes, cancer, and other conditions. L-citrulline’s antioxidative properties involve its transformation into another vital amino acid, L-arginine. This occurs within the body’s endothelial cells, which form a single cell layer lining all blood vessels. These amino acids’ effectiveness as antioxidants depends on the stress source.

L-arginine itself converts into a chemical called nitric oxide (NO), in a process called endothelial-nitric oxide synthase (eNOS). NO is responsible for crucial biological functions and also contributes to various risk factors and diseases, like type 2 diabetes. Additionally, NO acts as a vasodilator, widening the blood vessels. Excess free radicals can reduce NO bioavailability, worsening endothelial dysfunction, which is associated with cardiometabolic diseases, involving the heart, blood, and blood vessels.

L-Citrulline Benefits for All

A non-essential amino acid, L-citrulline may improve other amino acids’ effectiveness within the liver. L-citrulline is the common supplemental form, with nothing else attached. Our bodies produce it naturally in the liver and intestines, although taking supplements can increase nutritional levels. L-citrulline is crucial to the urea cycle, helping rid the body of harmful substances, and may support cardiovascular health, immunity, athletic performance, and depression. 

Please note: L-Citrulline supplements may not be appropriate for every person or situation. It’s important to discuss any supplementation with your doctor before starting a new regimen.

 L-Citrulline for Female Reproductive Health

By transforming into L-arginine, which converts into nitric oxide, L-citrulline may improve several female sexual health factors, including libido. Research shows that taking L-arginine and other nutrients together — specifically in a nutritional blend containing L-arginine, multivitamins,  minerals, and the herbs ginseng, ginkgo, and damiana — boosted sexual drive among premenopausal, perimenopausal, and postmenopausal women. 

L-citrulline is also important for pregnancy, improving such birth outcomes as placental vascular (blood vessel) development, fetal growth restriction, preterm birth, and low birth weight. Its transformation into L-arginine may also support the treatment and prevention of preeclampsia, a dangerous condition characterized by high blood pressure and protein in the urine.

 L-Citrulline for Male Fertility

L-citrulline may be one of the most crucial nutrients for male fertility, including sperm and semen health and quality. As it transforms into L-arginine, this stimulates sex glands, with their secretions affecting sperm formation. This helps to improve the quality of semen, including those for such criteria as quantity, motility, and morphology. 

L-citrulline may benefit male fertility in its role in nitric oxide production. NO is thought to function as a sex-enhancing neurotransmitter, helping to remove free radicals and promoting blood flow to the sex organs. One of L-citrulline’s most important benefits is how it improves erectile dysfunction, by playing a vital role in erection formation, keeping the endothelial cells free of harmful plaque. Its transformation into arginine and nitric oxide helps smooth arterial muscle cells relax, enabling blood to flow more freely, with less pressure against arterial walls. By producing arginine, L-citrulline may also help to maintain healthy levels of the male hormone, testosterone, even when lost to testicular damage. 

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Your Questions, Answered: L-Citrulline Fertility FAQ

  • Yes, L-citrulline has been shown to improve such birth outcomes as placental blood vessel development, fetal growth restriction, preterm birth, and low birth weight. It also may reduce high blood pressure during pregnancy, helping to prevent preeclampsia.

  • L-citrulline may impart some benefits for female fertility through its conversion into L-arginine and its role in the L-arginine-nitric oxide (NO) system, which plays a critical role in reproduction, including folliculogenesis (maturation of the ovarian follicles), oocyte maturation, fertilization, embryogenesis, implantation, placentation, pregnancy, and delivery. While supplementation may provide some protective effects against oxidative stress, more research is still needed.

  • Via its conversion into L-arginine, L-citrulline supplements may promote the treatment and prevention of preeclampsia. This dangerous condition, generally occurring after the 20th week of pregnancy, involves high blood pressure, protein in the urine, and organ damage. L-arginine may effectively lower blood pressure in affected women, and reduce risks with a higher likelihood of developing preeclampsia.

  • Yes, and research suggests that this amino acid may be one of the more important nutrients for sperm and semen health and quality. The conversion into L-arginine enables the stimulation of sex glands, and their secretions may promote sperm formation. It’s been shown that supplementation may help to improve the quality of semen, including for such criteria as quantity, total number, mobility, and semen antioxidant capacity, its total amount of activity. 

    Furthermore, a supplemental combination of L-citrulline, L-arginine, French maritime pine bark extract, and an oak wood extract (called roburins), was found to significantly improve sperm volume and concentration, motility, vitality, and morphology.

  • Yes, likely due to its role in nitric oxide formation, L-citrulline is crucial for erectile dysfunction. Essentially, via its role as a sex-enhancing neurotransmitter, NO helps to remove free radicals and promote blood flow to the sex organs. NO can relax arteries and small blood vessels, which can improve sexual response by maintaining the penis’ blood flow.

  • Yes, in its role as an L-arginine precursor, this amino acid has been found to defend men against testosterone loss occurring as the result of testicular damage. Among older men with erectile dysfunction, L-arginine also increased hormonal levels and helped with sexual dysfunction. Remarkably, these supplements may even benefit testosterone levels in men with testes damaged by heat or food poisoning.