Evidence supporting the use of: L-cysteine
For the health condition: Free Radical Damage

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Synopsis

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

L-cysteine is a sulfur-containing amino acid that plays a significant role in the body’s antioxidant defense system. Its use to support or treat free radical damage is primarily justified by scientific evidence. L-cysteine serves as a precursor for the synthesis of glutathione, one of the most potent intracellular antioxidants. Glutathione directly neutralizes reactive oxygen species (ROS) and other free radicals, thereby protecting cells from oxidative stress and damage.

Several studies have demonstrated that supplementation with L-cysteine or its more stable form, N-acetylcysteine (NAC), can increase glutathione levels in tissues. Enhanced glutathione availability helps combat oxidative stress in conditions such as liver disease, chronic obstructive pulmonary disease (COPD), and certain neurodegenerative disorders. For example, NAC is commonly used therapeutically to replenish glutathione in acetaminophen overdose, a scenario characterized by massive oxidative stress.

However, while animal and laboratory studies consistently show antioxidant benefits, the evidence in humans for general prevention or treatment of free radical damage is more mixed. Clinical trials often use NAC rather than pure L-cysteine, and results vary depending on the disease context and dosing. As a result, the overall evidence rating for L-cysteine’s use in mitigating free radical damage is moderate (3/5). More large-scale, high-quality clinical trials are needed to clarify its efficacy in the general population.

More about L-cysteine
More about Free Radical Damage

Other ingredients used for Free Radical Damage

1,2-di-galloyl-4,6hexahydroxydiphenoyl-D-glucose
3,3'-dihydroxy-B-carotene-4,4'-dione
3-Isomangostin
5,7-Dimethoxyflavone
7,4-Dimethoxyflavone
7-hydroxymatairesinol (HMR)
Acacetin
Acai berry
Acer truncatum
Acetyl L-carnitine
Algae
Algal protein
Allophycocyanin
Alpha-carotene
alpha-glycosyl isoquercitrin
alpha-lipoic acid
amentoflavone
amethoflavone
amino acids
ankaflavin
anthocyanidins
anthocyanins
anthocyanosides
antirrhinin
apigenin
apocarotenal
apocynin
apricot
arctiin
argan nut oil
Arjunolic acid
Aronia melanocarpa
ascorbigen
ascorbyl palmitate
astaxanthin
astragaloside
astragalus
Auricularia
Autumn Olive
avocado
baccosides
bacoside
baicalin
Basidiomycota
basil
bee pollen
benfotiamine
berry
beta-carotene
beta-hydroxybutyrate
beta-tocopherol
beta-zeacarotene
betanin
BHA (butylated hydroxyanisole)
BHT (butylated hydroxytoluene)
bilberry
bioflavonoids
black currant
black garlic
black tea
blackberry
blueberry
bok choy
boysenberry
Brassica
Brazil nut
broccoli
Brussel sprouts
C-phycocyanin
caffeic Acid
caffeine
Camellia sinensis
camu camu
canthaxanthin
capsanthin
capsorubin
carnosic acid
Carnosine
carnosol
carotene (unspecified)
cashew
catalase
catechins
caterpillar mushroom
cauliflower
chebulic acid
chebulinic acid
chocolate
chokeberry
chrysin
cichoric acid
cistanche
cocoa
coconut milk
coenzyme Q10 (CoQ10)
coffee fruit
crocetin
Crypthecodinium
cryptoxanthin
cupric ascorbate
dehydroascorbic acid
delphinidin
delta-tocopherol
desoxyrhaponticin
dibenzo-alpha pyrones
dihydrolipoic acid
diosmetin
dismutase
dragon fruit
Dumontiaceae
Dunaliella
Dunaliella salina
Ecklonia
ellagic acid
emblicanin
epicatechin
epigallocatechin gallate (EGCG)
ergothioneine
eriodictyol
erythorbic acid
ethylgallate
fatty acids
ferulic acid
fish protein
flavanones
flavans
flavin mononucleotide
flavoglycosides
flavones
flavonols
flavonones
fruit blend (proprietary)
fucoidan
fulvic acid
furanosterols
Gac
gamma-carotene
gamma-glutamylcysteine
ganoderma
Garcinone C
Garcinone E
ginseng
Ginsenosides
Glucan peptides
Glutathione
goji berry
grape
green tea
greens blend (proprietary)
guarana
Haematococcus pluvialis
hesperetin
hesperidin
HMR lignan
honeybush
hydroxycinnamic acid
hydroxyphenylethanols
hydroxytyrosol
Idebenone
isoascorbate
isovitexin
Jaboticaba
Kaempferol
kucha tea
L-carnosine
L-cysteine
L-glutathione
L-glycine
Lentinula edodes mycelia
Leucodelphinidin
lingzhi
lipids
lutein
Lycium
macadamia
malvidin
mangiferin
mangostanol
mangostene xanthone
Matcha
Mate
Melatonin
Methoxylated flavones
Methylselenocysteine
Mineral ascorbate
mixed carotenoids
Myricitrin
N-acetyl-cysteine (NAC)
N-Caffeoyldopamine
Neoandrographolides
Neoxanthin
nicotinamide riboside
Oligomeric proanthocyanidins
omega-3 fatty acids
oyster mushroom
papaya
Pecan
Pentacyclic triterpenoids
Pentose phosphate
phenolic compounds
Phosphate ascorbate
phospholipids
Phthalides
Phycocyanin
Phytoene
Phytofluene
Phytoplankton
pine bark
Plankton
Pleurotus eryngii
polymethoxylated flavones
polyphenols
polyporous mushroom
proanthocyanidins
procyanidin
procyanidol
propyl gallate
punicalagins
punicosides
Pycnogenol
pyrroloquinoline disodium salt
pyrroloquinoline quinone
quercetin
raspberry
reishi mushroom
resveratrol
rhammetin
Ribose-l-cysteine
robusta coffee
Rooibos
rosmarinic acid
royal jelly
Salidroside
Schisandrins
Scopoletin
selenium
Sesamolin
Shilajit
Silychristin
spirulina
Squalene
strawberry
Tangeretin
Taxifolin
Theaflavin
Tiliroside
Tremella
Trigalloyl glucose
turmeric
Tyrosol
ubiquinol
Uncaria
Vanillin
vegetable blend (proprietary)
Vestitol
vitamin C
vitamin E
Walnut
wheat germ
Whey protein
White Tea
Withanolides
Xanthone
Xanthophyll
Xylaria nigripes
Yumberry
Zinc

Products containing L-cysteine

Metagenics BioPure Protein® Powder
Metagenics Bone Builder Active
Metagenics Clear Change 10-Day Detox Program with UltraClear Plus Berry
Metagenics Clear Change 10-Day Detox Program with UltraClear Plus pH
Metagenics Clear Change 10-Day Detox Program with UltraClear Plus pH Pineapple Banana
Metagenics Clear Change 10-Day Detox Program with UltraClear Plus Pineapple Banana
Metagenics Clear Change 10-Day Detox Program with UltraClear Plus Vanilla
Metagenics Clear Change 28-Day Detox Program with UltraClear Plus Berry
Metagenics Clear Change 28-Day Detox Program with UltraClear Plus pH Pineapple Banana
Metagenics Clear Change 28-Day Detox Program with UltraClear Plus pH Vanilla
Metagenics Clear Change 28-Day Detox Program with UltraClear Plus Pineapple Banana
Metagenics Clear Change 28-Day Detox Program with UltraClear Plus Vanilla
Metagenics Collagenics®
Metagenics Echinacea Synergy
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
Metagenics UltraGI Replenish Vanilla
Metagenics UltraInflamX Plus 360°® Chocolate/Orange
Metagenics UltraInflamX Plus 360° Mango
Metagenics UltraInflamX Plus 360° Mango
Metagenics UltraInflamX Plus 360° Orange
Metagenics UltraInflamX Plus 360° Original Spice
Metagenics UltraInflamX Plus 360° Pineapple/Banana
Metagenics UltraInflamX Plus 360° Pineapple/Banana
Metagenics UltraMeal Advanced Protein® Dutch Chocolate
Metagenics UltraMeal Advanced Protein French Vanilla
Metagenics UltraMeal Advanced Protein Plain
Metagenics UltraMeal Cardio 360°® Pea/Rice Chocolate
Metagenics UltraMeal Cardio 360° Pea/Rice Vanilla