Betaine

Endpoint summary

Link to relevant study record(s)

Reference

Endpoint:

basic toxicokinetics in vivo

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Objective of study:

metabolism

Principles of method if other than guideline:

Review article of a well-established metabolism route for betaine, oxidation product of choline within the human body.

GLP compliance:

no

Species:

human

Sex:

male/female

Route of administration:

oral: feed

Vehicle:

not specified

Type:

metabolism

Results:

Completely metabolized by liver and kidney cells by methylation to dimethylglycine and ultimately to serine.

Metabolites identified:

yes

Details on metabolites:

Dimethylglycine

Conclusions:

Betaine is completely metabolized by liver and kidney cells, a very small amount is passed in urine.

Executive summary:

Completely metabolized by liver and kidney cells by methylation to dimethylglycine and ultimately to serine; a very small amount is passed in urine.

Description of key information

Betaine can be found in the human body as a naturally occurring substance, it is formed within the body from the oxidation of choline. Betaine (also known as trimethylglycine) is further metabolized first to dimethylglycine and ultimately to glycine and sarcosine. Betaine acts as an osmolyte and protectant against adverse phenomena within the body, and is involved in one-carbon metabolism and methylation processes. Betaine's main action is to donate a methyl group to homocysteine, which then is subsequently metabolized to methionine.

Key value for chemical safety assessment

Bioaccumulation potential:

no bioaccumulation potential

Additional information

Betaine can be found in the human body as a naturally occurring substance, it is formed within the body from the oxidation of choline. Betaine acts as an osmolyte and protectant against adverse phenomena within the body, and is involved in one-carbon metabolism and methylation processes. Betaine's main action is to donate a methyl group to homocysteine, which then is subsequently metabolized to methionine. Betaine (also known as trimethylglycine) itself is metabolized first to dimethylglycine and ultimately to glycine and sarcosine.

Humans can consume betaine from normal food stuffs such as vegetables, seafood and wheat, since betaine occurs in nature mainly as protectant of stress, especially osmotic stress. Betaine is metabolized mainly by the liver but also by kidney cells. Betaine has been found safe in various nutritional and pharmacokinetic human studies, as well as in a wide range of toxicity testing in animals following OECD guidelines in GLP conditions. Betaine is used in feed for animals and is approved as a supplement or nutrient for human consumption in several geographic regions.

The emphasis of human studies has mostly been to investigate how betaine improves health, especially in the case of a metabolic disorder called homocystinuria, where betaine is approved by the US-FDA for the treatment of this disorder. When detected from serum, betaine is metabolized within 24 hours by the body (highest dose 6g, with the single dose of 50mg/kg elimination half-life was approximately 14 hours, continuous approximately 5 days). When studying the activity of the betaine metabolizing enzyme, betaine homocysteine methyltransferase (BMHT), in animals, adaptation for higher doses of betaine has been detected in rats. Excess betaine is excreted via urine. Dermal absorption of betaine is extremely low as tested in the in vitro-setting. Attachment: betaine metabolism - schematic diagram.