Evidence supporting the use of: L-cysteine
For the health condition: Colds (general)

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Synopsis

Source of validity: Scientific
Rating (out of 5): 3

L-cysteine, particularly in the form of its derivative N-acetylcysteine (NAC), has some scientific evidence supporting its use in the context of respiratory infections, including the common cold. L-cysteine is a precursor to glutathione, a potent antioxidant that helps protect cells from oxidative stress induced by infections. Several studies have explored the use of NAC for respiratory tract infections; for example, a notable randomized controlled trial found that NAC reduced the frequency and severity of influenza-like episodes in elderly subjects. NAC's mucolytic (mucus-thinning) properties are beneficial in loosening mucus, which can help alleviate cough and congestion associated with colds. Although most research focuses on NAC rather than L-cysteine itself, the underlying mechanism—supporting glutathione production and reducing oxidative stress—applies to both compounds. While L-cysteine is not a traditional remedy for colds, and is not as commonly discussed as vitamin C or zinc for immune support, its scientific basis stems from its biochemical role and the positive outcomes seen in studies of its derivative. The evidence is moderate (rated 3/5) because, while there are promising results, most clinical trials have focused on NAC, and results for the common cold specifically (as opposed to more severe respiratory infections) are less robust. Nonetheless, L-cysteine supplementation may offer some benefit in supporting the body's antioxidant defenses during a cold.

More about L-cysteine
More about Colds (general)

Other ingredients used for Colds (general)

3-(4-hydroxy-3-methoxyphenyl)prop-2-enoic acid
Abies spectabilis
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Acacia
Aconite
Aerva lanata
Agastache
Ajuga
Alcohol
Algae
Allicin
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Allium tuberosum
Allspice
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Allyl sulfide
Aloe vera
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alpinia galangal
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Amor seco
anamu
Andrographis
andrographolide
Angelica
anthocyanins
apple
apple cider vinegar
arabinogalactan
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Asam gelugor
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ash
aster root
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astragalus
atractylodes
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bael
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black galingale
black garlic
black nightshade
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black salt
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black tea
blackberry
blackboard tree
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Blepharis
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Boerhavia diffusa
Bombax
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Borassus aethiopum
borassus palm
borneol
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bupleurum falcatum
bur-reed
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bасора
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capillary artemisia
capsaicin
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Carthamus
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caterpillar mushroom
cayenne pepper
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fulvic acid
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iridoid glycosides
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Spikenard
spirulina
spruce
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vitamin B
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xanthium (cockleburs)
Yeast
Yellow-Fruit Nightshade
Yerba buena
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Yuzu
zanthoxylum
Zinc
Zingerone
Zingiberene
Zucchini

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Metagenics Clear Change 10-Day Detox Program with UltraClear Plus Berry
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Metagenics Collagenics®
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Metagenics GI Sustain™ Powder
Integrative Therapeutics Glutathione Cell Defense
Vitabase Hair, Skin & Nails Formula
Metagenics ImmuCore
Metagenics Immune Defense Pack
Designs For Health PaleoCleanse Plus™
Designs For Health PaleoCleanse Plus™
Designs For Health PaleoCleanse Plus™ Detox Program
Designs For Health PaleoCleanse Plus™Chocolate Detox Kit
Metagenics Perfect Protein® Pea & Rice Chocolate Powder
Metagenics Perfect Protein Pea & Rice Vanilla Powder
Metagenics Perfect Protein Whey Chocolate
Metagenics Perfect Protein Whey Vanilla
Designs For Health Plant Protein Cleanse
Designs For Health Plant Protein Cleanse Plus™ 570g
Vitabase Super Antioxidant Formula
Metagenics Ultra Glucose Control® Chocolate
Metagenics Ultra Glucose Control Chocolate
Metagenics Ultra Glucose Control Vanilla
Metagenics Ultra Glucose Control Vanilla
Metagenics Ultra Potent-C 1000
Metagenics Ultra Potent-C 500
Metagenics Ultra Potent-C Chewable
Metagenics Ultra Potent-C Powder
Metagenics UltraClear Detox Powder
Metagenics UltraClear Plus® Detox Powder
Metagenics UltraClear Plus Detox Powder Berry
Metagenics UltraClear Plus Detox Powder Pineapple/Banana
Metagenics UltraClear Plus pH Detox Powder Pineapple/Banana
Metagenics UltraClear Plus pH Detox Powder Vanilla
Metagenics UltraGI Replenish® Chocolate
Metagenics UltraGI Replenish Chocolate
Metagenics UltraGI Replenish Vanilla
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Metagenics UltraInflamX Plus 360°® Chocolate/Orange
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Metagenics UltraInflamX Plus 360° Orange
Metagenics UltraInflamX Plus 360° Original Spice
Metagenics UltraInflamX Plus 360° Pineapple/Banana
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Metagenics UltraMeal Advanced Protein® Dutch Chocolate
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Metagenics UltraMeal Advanced Protein Plain
Metagenics UltraMeal Cardio 360°® Pea/Rice Chocolate
Metagenics UltraMeal Cardio 360° Pea/Rice Vanilla