What is L-Proline?
L-proline is a non-essential amino acid and one of the main components of collagen, the most abundant
structural protein in the human body. Proline is sometimes referred to as an imino acid, as it has a
secondary imine group instead of a primary amine group. It is structurally unique, as it connects to its
protein backbone twice to form a five-member nitrogenous ring. In addition to making collagen, proline helps
to biosynthesize proteins, repair skin tissues, and improve antioxidant status.
The body can synthesize proline from l-glutamate, but certain nutrient deficiencies can interfere with this
process. For example, the body needs ascorbic acid (vitamin C) to
hydroxylate proline residues in collagen. Proline hydroxylation dramatically increases collagen stability
and is critical for maintaining connective tissues. Without sufficient vitamin C, defective collagen forms
and can cause numerous health problems.
Potential L-Proline Benefits
Proline for Youthful, Resilient Skin
Proline, along with glycine, is a primary amino acid required to synthesize collagen. It accounts for 15% of
all the collagen in the body. Combined with glycine and hydroxyproline, it comprises over half of collagen’s
amino acid content. Supporting collagen synthesis promotes wound healing by strengthening the structure of
the skin and improving the skin barrier. Collagen is also responsible for skin firmness, tightness, and
tone. However, collagen production decreases with age and takes a toll on the skin’s appearance. Proline
supplements may help improve the visible signs of aging by boosting collagen formation. One study noted
proline supplements helped smooth and improve the appearance of cellulite in women.
Proline and Gut Health
Digestive health is a strong indicator of immune function. Collagen supports gut health by strengthening GI
tract tissues for better nutrient absorption. Collagen amino acids also boost the body’s immune defenses
against toxins, foreign substances, and pathogens. One study noted that proline reduces oxidative stress by
scavenging reactive oxygen free radicals and increasing the activity of existing antioxidants in plants.
Prolonged oxidative stress damages the immune system and contributes to numerous health problems.
Proline and Joint Health
Collagen synthesis begins to decline around the age of 30, and joint pain often increases as a result.
Collagen is critical for maintaining connective tissues, cartilage, and bone density. It also cushions
joints and repairs cartilage. Taking proline supplements may improve joint pain by promoting collagen
Proline for Exercise Performance
Proline may enhance athletic performance. One study found that a vitamin C-enriched gelatin supplement
increased circulating levels of proline, hydroxyproline, hydroxylysine, and glycine for superior collagen
synthesis. Increased collagen levels help repair muscle tissues and reduce the likelihood of
exercise-related injuries by protecting muscles, joints, and ligaments.
Potential L-Proline Side Effects
Most individuals can take proline supplements without experiencing adverse effects. However, ingesting large
quantities of amino acids causes the body to create protein waste, which it must excrete through the liver
and kidneys. Individuals with liver or kidney conditions should consult with a physician before taking
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