Verifiable Science
Glutathione is one of the main endogenous
antioxidants. Found in virtually every cell of the
body, glutathione defends against free radicals, in
part by recycling other antioxidants. It also
supports detoxification and other critical aspects of
cell function.[1]
Increased glutathione levels have
been linked to supporting a reduction in oxidative
stress and DNA damage. Cysteine and glycine are
necessary precursors for glutathione (GSH)
synthesis, but the required amounts may not be met
by dietary intake alone, particularly as we age.[2]
Co-
supplementation of these nutrients has been shown
to promote intracellular glutathione levels. In a
small study involving older individuals, two weeks of
supplementation with a combination of N-acety-l-
cysteine (NAC) and glycine raised red blood cell
(RBC) glutathione levels more effectively than either
amino acid alone. In one study, supplementation
with the combination of NAC and glycine resulted in
32% higher RBC glycine, 46% higher RBC cysteine
and a 53% increase in RBC GSH concentration.
There was also a significant improvement in the
ratio of reduced (active) GSH to oxidized glutathione
(GSSG).[3]
Increased GSH was associated with
improvement in antioxidant status as measured by
F2-isoprostanes, as well as mitochondrial fatty acid
oxidation. In another study comparing young and
older subjects, elderly subjects had 55% lower RBC
glycine, 24% lower RBC cysteine, and 46% lower
RBC glutathione at baseline, as well as lower
reduced (active) GSH to GSSG ratios.[4,5]
Supplementation with NAC and glycine in elderly
subjects resulted in RBC levels of glycine, cysteine,
and glutathione, as well as GSH:GSSG ratio,
comparable to young unsupplemented subjects.[6]
NAC and glycine have been shown to maintain
healthy cytokine release during times of metabolic
stress.7 Research suggests that glycine may
moderate TNF and promote IL-10 to support
cytokine balance, and that glycine intake is
positively associated with cardiometabolic health.[7,8]
Studies indicate that supplementation with NAC
also supports mood and social functioning. It is
believed that cysteine influences the reward-
reinforcement pathway by modulating the
glutamate system.[9]
NAC additionally promotes
immune defenses and supports the health of
epithelial cells and cilia in the respiratory tract. The
affinity of NAC for lung tissue, together with its
natural sulfur content, allows it to disrupt disulfide
bonds within mucus, thinning and easing its
expulsion. In a randomized, double-blind trial
involving mostly older individuals, 600 mg of NAC
twice daily showed significant support for
respiratory and immune function.[10,11,12,13]‡
References
- Richie JP Jr, et al. Eur J Nutr. 2015 Mar;54(2):251-63.
- Zhang Q, et al. Medicine (Baltimore). 2018 Nov;97(45).
- Sekhar RV, et al. Am J Clin Nutr. 2011 Sep;94(3):847-53.
- Roes EM, et al. Clin Chem Lab Med. 2002 May;40(5):496-8.
- Guthikonda, et al. American Geriatrics Society Annual Scientific Meeting. 2006.
- Nguyen D, et al. J Clin Endocrinol Metab. 2014 Jan;99(1):169-77.
- Cruz M, et al. J Endocrinol Invest. 2008 Aug;31(8):694-9.
- Ding, et al. Circ Cardiovasc Genet. 2016 Dec;9(6):541-547.
- Berk M, et al. Biol Psychiatry. 2008 Sep 15;64(6):468-75.
- Grant JE, et al. Arch Gen Psychiatry. 2009 Jul;66(7):756-63.
- Ozdemir ZC, et al. Hemoglobin. 2014;38(5):359-64.
- Tse HN, et al. Chest. 2013 Jul;144(1):106-18.
- De Flora S, et al. Eur Respir J. 1997 Jul;10(7):1535-41.