• Supports the production of glutathione *

    • Supports antioxidant defenses *

    • Supports healthy immune responses *


L-cystine is the chief sulfur-containing compound in protein. It is found in eggs, meat, dairy products, and whole grain foods. L-cystine is the disulfide form of L-cysteine, which means it consists of two molecules of L-cysteine—this is why it is occasionally referred to as dicysteine—bonded together at their sulfur groups. Inside cells, L-cystine is metabolized into L-cysteine, which, along with glutamine and glycine, is used to make an important detoxification and antioxidant molecule called “glutathione”[1]. L-cysteine availability limits the rate of glutathione production (it is thought to be rate-limiting) [1]. Supplying L-cystine allows the body to restore intracellular glutathione levels when demand has been increased or under circumstances when it is lower (such as older age or increased toxin exposure) in tissues throughout the body (including the brain, liver, and muscles). L-cystine promotes glutathione-related antioxidant defenses, which helps protect cells and mitochondria against free radicals, cell membrane damage, damage from metals and toxins, and other oxidative stress-related and aging issues. L-cystine plays important structure and function roles in immune cells, skeletal muscle, and connective tissue. Hair and skin contain approximately 10–14% cystine by mass.


Antioxidant defenses


  • Supports glutathione levels [3–5]

  • Regulates mitochondrial ROS production [6]

  • Support brain glutathione levels [7]

  • Supports neuroprotection (secondary to boosting glutathione and antioxidant defenses) [7–10]

  • Supports gut glutathione levels [11]




  • Supports general immune health [3,12–15]

  • Supports post-exercise immunity [13,14,16]

  • Supports innate immunity [13,14,16]

  • Supports adaptive immunity [3,13,16,17]

  • Supports immune signaling [3–5,17,18]

  • Supports healthy natural killer cell function [14]

  • Supports healthy neutrophil function [13,16]

  • Supports healthy lymphocyte function [13,16,17]

  • Supports healthy antibody responses [3,17]

  • Supports T cell glutathione production [19]

  • Supports gut barrier function [11,20]

  • Supports gut immune signaling [20]


Complementary ingredients


  • L-Theanine in support of general immune health [3,12–17,21]

  • Glycine in support of glutathione synthesis [22,23]


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[2]Institute of Medicine, Food and Nutrition Board, Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids, National Academies Press, 2005.

[3]Y. Takagi, S. Kurihara, N. Higashi, S. Morikawa, T. Kase, A. Maeda, H. Arisaka, S. Shibahara, Y. Akiyama, J. Vet. Med. Sci. advpub (2010) 0911170039–0911170039.

[4]T. Shibakusa, T. Mikami, S. Kurihara, Y. Chiba, T. Tsuchiya, T. Miyachi, A. Oyama, K.A.K. Tanaka, N. Koyama, Clin. Nutr. 31 (2012) 555–561.

[5]T. Miyakuni, K. Fukatsu, M. Ri, S. Murakoshi, Y. Inoue, S. Kurihara, T. Takayama, H. Yasuhara, Ann. Nutr. Metab. 73 (2018) 131–137.

[6]A. Gomez, J. Gomez, M. Lopez Torres, A. Naudi, N. Mota-Martorell, R. Pamplona, G. Barja, J. Bioenerg. Biomembr. 47 (2015) 199–208.

[7]E. Ignowski, A.N. Winter, N. Duval, H. Fleming, T. Wallace, E. Manning, L. Koza, K. Huber, N.J. Serkova, D.A. Linseman, Free Radic. Biol. Med. 124 (2018) 328–341.

[8]A.N. Winter, E.K. Ross, V. Daliparthi, W.A. Sumner, D.M. Kirchhof, E. Manning, H.M. Wilkins, D.A. Linseman, Oxid. Med. Cell. Longev. 2017 (2017) 3103272.

[9]C. Liapi, A. Zarros, S. Theocharis, K. Voumvourakis, F. Anifantaki, E. Gkrouzman, Z. Mellios, N. Skandali, H. Al-Humadi, S. Tsakiris, Biol. Trace Elem. Res. 143 (2011) 1673–1681.

[10]C. Liapi, A. Zarros, S. Theocharis, H. Al-Humadi, F. Anifantaki, E. Gkrouzman, Z. Mellios, N. Skandali, S. Tsakiris, Biometals 22 (2009) 329–335.

[11]M.T.J. van Ampting, A.J. Schonewille, C. Vink, R.J.M. Brummer, R. van der Meer, I.M.J. Bovee-Oudenhoven, BMC Physiol. 9 (2009) 6.

[12]K. Miyagawa, Y. Hayashi, S. Kurihara, A. Maeda, Geriatr. Gerontol. Int. 8 (2008) 243–250.

[13]S. Murakami, S. Kurihara, N. Koikawa, A. Nakamura, K. Aoki, H. Yosigi, K. Sawaki, M. Ohtani, Biosci. Biotechnol. Biochem. 73 (2009) 817–821.

[14]S. Kawada, K. Kobayashi, M. Ohtani, C. Fukusaki, J. Strength Cond. Res. 24 (2010) 846–851.

[15]S. Kurihara, T. Hiraoka, M. Akutsu, E. Sukegawa, M. Bannai, S. Shibahara, J. Amino Acids 2010 (2010) 307475.

[16]S. Murakami, S. Kurihara, C.A. Titchenal, M. Ohtani, J. Int. Soc. Sports Nutr. 7 (2010) 23.

[17]S. Kurihara, S. Shibahara, H. Arisaka, Y. Akiyama, J. Vet. Med. Sci. 69 (2007) 1263–1270.

[18]K.A.K. Tanaka, S. Kurihara, T. Shibakusa, Y. Chiba, T. Mikami, Clin. Nutr. 34 (2015) 1159–1165.

[19]T.B. Levring, M. Kongsbak, A.K.O. Rode, A. Woetmann, N. Ødum, C.M. Bonefeld, C. Geisler, Oncotarget 6 (2015) 21853–21864.

[20]C.J. Kim, J. Kovacs-Nolan, C. Yang, T. Archbold, M.Z. Fan, Y. Mine, Biochim. Biophys. Acta 1790 (2009) 1161–1169.

[21]S. Kurihara, T. Shibakusa, K.A. Tanaka, Springerplus 2 (2013) 635.

[22]R.V. Sekhar, S.G. Patel, A.P. Guthikonda, M. Reid, A. Balasubramanyam, G.E. Taffet, F. Jahoor, Am. J. Clin. Nutr. 94 (2011) 847–853.

[23]D. Nguyen, J.W. Hsu, F. Jahoor, The Journal of Clinical (2014).