Betaine is involved in protein synthesis which is one of the main cellular functions (1).

Serum levels of choline and betaine showed strong prognostic value for the prediction of colon incidents, suggesting a role of choline and betaine metabolism in the pathogenesis of colon cancer (2).

Cholesterol is essential for neuronal development and brain function. Administration of betaine in ovo modulates hepatic cholesterol metabolism (3).

Other studies

Treatable cause of hereditary spastic paraplegia: eight cases of combined homocysteinaemia with methylmalonic aciduria.  Wei Y, Zhou Y, Yuan J, Ni J, Qian M, Cui L, Peng B.  J Neurol. 2019 Jun 15. doi: 10.1007/s00415-019-09432-8

Influence of fibre and betaine on development of the gastrointestinal tract of broilers between hatch and 14 d of age.  Santos TTD, Dassi SC, Franco CRC, Costa CRVD, Lee SA, Fisher da Silva AV.  Anim Nutr. 2019 Jun;5(2):163-173. doi: 10.1016/j.aninu.2018.06.005.

Alleviation of infectious-bursal-disease-virus-induced bursal injury by betaine is associated with DNA methylation in IL-6 and interferon regulatory factor 7 promoter.  Zhang Y, Yu Y, Ou C, Ma J, Wang Q, Du S, Xu Z, Li R, Guo F.  Poult Sci. 2019 Jun 4. pii: pez280. doi: 10.3382/ps/pez280.

Conjugated linoleic acid and betaine affect lipolysis in pig adipose tissue explants.  Fernández-Fígares I, Lachica M, Martínez-Pérez M, Ramsay TG.  Animal. 2019 May 31:1-7. doi: 10.1017/S1751731119001186.

Effects of dietary supplementation with betaine on muscle growth, muscle amino acid contents and meat quality in Cherry Valley ducks.  Chen R, Wen C, Cheng Y, Chen Y, Zhuang S, Zhou Y.  J Anim Physiol Anim Nutr (Berl). 2019 May 29. doi: 10.1111/jpn.13083

Structural and molecular aspects of betaine-GABA transporter 1 (BGT1) and its relation to brain function.  Kickinger S, Hellsberg E, Frølund B, Schousboe A, Ecker GF, Wellendorph P.  Neuropharmacology. 2019 May 18. pii: S0028-3908(19)30170-4. doi: 10.1016/j.neuropharm.2019.05.021.

Untargeted metabolomics reveals N, N, N-trimethyl-L-alanyl-L-proline betaine (TMAP) as a novel biomarker of kidney function.  Velenosi TJ, Thomson BKA, Tonial NC, RaoPeters AAE, Mio MA, Lajoie GA, Garg AX, House AA, Urquhart BL.  Sci Rep. 2019 May 2;9(1):6831. doi: 10.1038/s41598-019-42992-3.

Effects of Dietary Rumen-Protected Betaine Supplementation on Performance of Postpartum Dairy Cows and Immunity of Newborn Calves.  Wang B, Wang C, Guan R, Shi K, Wei Z, Liu J, Liu H.  Animals (Basel). 2019 Apr 15;9(4). pii: E167. doi: 10.3390/ani9040167

Dietary choline and betaine intakes and risk of total and lethal prostate cancer in the Atherosclerosis Risk in Communities (ARIC) Study.  Han P, Bidulescu A, Barber JR, Zeisel SH, Joshu CE, Prizment AE, Vitolins MZ, Platz EA.  Cancer Causes Control. 2019 Apr;30(4):343-354. doi: 10.1007/s10552-019-01148-4.

Maternal Choline and Betaine Supplementation Modifies the Placental Response to Hyperglycemia in Mice and Human Trophoblasts.  Nanobashvili K, Jack-Roberts C, Bretter R, Jones N, Axen K, Saxena A, Blain K, Jiang X.  Nutrients. 2018 Oct 15;10(10). pii: E1507. doi: 10.3390/nu10101507.

References_____________________________________________

(1) Cap-independent protein synthesis is enhanced by betaine under hypertonic conditions.
Carnicelli D, Arfilli V, Onofrillo C, Alfieri RR, Petronini PG, Montanaro L, Brigotti M.
Biochem Biophys Res Commun. 2017 Feb 12;483(3):936-940. doi: 10.1016/j.bbrc.2017.01.035.

(2) Serum Trimethylamine N-oxide, Carnitine, Choline and Betaine in Relation to Colorectal Cancer Risk in the Alpha Tocopherol and Beta Carotene Study.
Guertin KA, Li XS, Graubard BI, Albanes D, Weinstein SJ, Goedert JJ, Wang Z, Hazen SL, Sinha R.
Cancer Epidemiol Biomarkers Prev. 2017 Jan 11. pii: cebp.0948.2016. doi: 10.1158/1055-9965.EPI-16-0948.

(3) Prenatal betaine exposure modulates hypothalamic expression of cholesterol metabolic genes in cockerels through modifications of DNA methylation.
Idriss AA, Hu Y, Sun Q, Jia L, Jia Y, Omer NA, Abobaker H, Zhao R.
Poult Sci. 2016 Dec 13. pii: pew437.

Betaine (1-carboxy-N, N, N-trimethyl-methanamine) is a quaternary ammonium compound, a partially modified amino acid derived from glycine, a natural substance (it was discovered in Beta vulgaris, the beet, in the 19th century) that is non-toxic and very stable. It is also called trimethylglycine because it has the appearance of three extra methyl groups.

It is found in wheat, spinach, beetroot, aquatic invertebrates and more. Its intake in the human body, where it is distributed in the kidneys, liver and brain, is considered safe if within the daily dietary dose recommended by the treating physician (1). It reduces protein denaturation and maintains enzyme activity. Betaine is an important component of the methionine cycle, essential for DNA gene regulation (2).

Commercially it occurs as a fine, white, crystalline, scaly or prismatic powder with a slightly sweet odour). Hygroscopic. Incompatible with strong oxidising agents.

What it is used for and where

Medical

Betaine improves the metabolism of sulphur amino acids against oxidative stress and thus has a positive effect on diabetes, obesity, cancer and neurodegenerative diseases thanks to its anti-inflammatory effect, which has been demonstrated for decades in the scientific literature (3).

Since high plasma homocysteine (an amino acid) poses a high risk of cardiovascular disease in the human body, a group of researchers at Wageningen University in the Netherlands, following a study on healthy subjects, concluded that a fasting dietary intake rich in betaine reduces plasma concentrations of homocysteine and post-methionine (4).

Cosmetics

Betaine is included in skin care products as a nutrient to prevent shrinkage or tissue decay of cells. It also works as a good cleanser.

Hair conditioning agent. A large number of ingredients with specific purposes can co-exist in a hair shampoo: cleansers, conditioners, thickeners, mattifying agents, sequestering agents, fragrances, preservatives, special additives. However, the indispensable ingredients are the cleansers and conditioners as they are necessary and sufficient for hair cleansing and manageability. The others act as commercial and non-essential auxiliaries such as: appearance, fragrance, colouring, etc. Hair conditioning agents have the task of increasing shine, manageability and volume, and reducing static electricity, especially after treatments such as colouring, ironing, waving, drying and brushing. They are, in practice, dispersing agents that may contain cationic surfactants, thickeners, emollients, polymers. The typology of hair conditioners includes: intensive conditioners, instant conditioners, thickening conditioners, drying conditioners.

Skin conditioning agent -  Humectant. Humectants are hygroscopic substances used to minimise water loss in the skin and to prevent it from drying out by facilitating faster and greater absorption of water into the stratum corneum of the epidermis. The epidermis is the most superficial of the three layers that make up the human skin (epidermis, dermis and hypodermis) and is the layer that maintains hydration in all three layers. In turn, the epidermis is composed of five layers: corneum, the most superficial, lucidum, granulosum, spinosum and basale. Humectants have the ability to retain in the stratum corneum the water they attract from the air and have the function of moisturising the skin. It is better to use them before emollients that are oil-based.

In toothpastes, it is included as a humectant to prevent a dry mouthfeel.

Animal feed

Feed additive. 

Other uses

Snacks, beverages, chocolate creams, cereals, nutrition bars, sports bars, vitamin tablets, filling capsules, etc.

Betaine studies

Typical optimal commercial product characteristics  Trimethylglycine

• Molecular Formula C₅H₁₁NO₂
• Linear Formula (CH₃)₃N⁺CH₂COO^-
• Molecular Weight 117.148 g/mol
• UNII: 3SCV180C9W
• CAS   590-46-5  107-43-7   590-30-7  11042-12-9  24980-93-6  45631-77-4
• EC Number: 203-490-6  209-683-1
• UNII    3SCV180C9W
• FEMA Number: 4223
• PubChem Substance ID 329748928
• MDL number MFCD00012123
• DSSTox Substance ID 
• IUPAC  2-(trimethylazaniumyl)acetate
• InChI=1S/C5H11NO2/c1-6(2,3)4-5(7)8/h4H2,1-3H3
• InChl Key      KWIUHFFTVRNATP-UHFFFAOYSA-N
• SMILES   C[N+](C)(C)CC(=O)[O-]
• ChEBI  17750
• JECFA     4223
• NSC   166511  
• Beilstein Registry Number 3537113

Synonyms: 

• glycine betaine
• oxyneurine
• lycine
• Betafin BCR
• 2-(Trimethylammonio)ethanoic acid, hydroxide, inner salt
• 2-trimethylammonioacetate
• 1-carboxy-n,n,n-trimethyl-methanaminium
• Methanaminium, 1-carboxy-N,N,N-trimethyl-, hydroxide, inner salt
• N,N,N-trimethylammonioacetate
• Loramine AMB-13
• (Carboxymethyl)trimethylammonium hydroxide inner salt
• (Carboxymethyl)trimethylammonium inner salt
• 3SCV180C9W
• 1-Carboxy-N,N,N-trimethylmethanaminium hydroxide, inner salt
• 2-N,N,N-trimethylammonio acetate
• 1-Carboxy-N,N,N-trimethylmethanaminium inner salt
• Novobetaine
• .alpha.-Earleine
• Hepastyl
• 2-(trimethylamino)acetic acid
• Glykokollbetain
• trimethylglycocoll anhydride
• Trimethylglycine
• Abromine
• (Carboxymethyl)trimethylammonium hydroxide, inner salt
• Trimethylglycocoll
• Glycylbetaine
• Glycocoll betaine
• acidin-pepsin
• alpha-Earleine
• Cystadane
• 1-carboxy-N,N,N-trimethyl-Methanaminium hydroxide
• methanaminium, carboxy-N,N,N-trimethyl-, inner salt
• Methanaminium,N,N-trimethyl-, hydroxide, inner salt
• (Carboxymethyl)trimethylammonium inner salt; Oxyneurine
• Methanaminium, 1-carboxy-N,N,N-trimethyl-, inner salt (9CI)
• Ammonium compounds, substituted, (carboxymethyl)trimethyl-, hydroxide, inner salt (7CI)
• Rubrine C
• Jortaine
• Trimethylaminoacetic acid
• Loramine AMB 13
• trimethylammonioacetate
• N,N,N-trimethylglycine
• Trimethylaminoacetate
• Glycine, trimethylbetaine
• Betaine hydrochloride
• 2-(trimethylazaniumyl)acetate
• (Trimethylammonio)acetate
• BETAINE, ANHYDROUS
• Betafin
• 2-(Trimethylammonio)Acetate
• Glykokollbetain [German]
• Acidol
• Methanaminium, 1-carboxy-N,N,N-trimethyl-, inner salt
• Aminocoat
• Greenstim
• FinnStim
• Betafin BP

References_______________________________________________________________________

(1) Craig SA. Betaine in human nutrition. Am J Clin Nutr. 2004 Sep;80(3):539-49. doi: 10.1093/ajcn/80.3.539.

(2)  Hu Y, Sun Q, Liu J, Jia Y, Cai D, Idriss AA, Omer NA, Zhao R. In ovo injection of betaine alleviates corticosterone-induced fatty liver in chickens through epigenetic modifications. Sci Rep. 2017 Jan 6;7:40251. doi: 10.1038/srep40251.

(3) Zhao G, He F, Wu C, Li P, Li N, Deng J, Zhu G, Ren W, Peng Y. Betaine in Inflammation: Mechanistic Aspects and Applications. Front Immunol. 2018 May 24;9:1070. doi: 10.3389/fimmu.2018.01070. 

(4) Olthof MR, van Vliet T, Boelsma E, Verhoef P. Low dose betaine supplementation leads to immediate and long term lowering of plasma homocysteine in healthy men and women. J Nutr. 2003 Dec;133(12):4135-8. doi: 10.1093/jn/133.12.4135.