Betaine is a derivative of the nutrient choline; in other words, choline is a “precursor” to betaine and must be present for betaine to be synthesized in the human body. Betaine is created by choline in combination with three methyl radicals and glycine, an aminoacid. Therefore, Betaine is known as trimethylglycine (TMG) and the human body is able to synthesized it. It’s involved in liver function, cellular reproduction, and helping make carnitine. It also helps the body metabolize an amino acid called homocysteine.
Just like some B vitamins, including folate andvitamin B12, betaine is considered to be a “methyl donor.” This means it aids in liver function, detoxification and cellular functioning within the body. It’s most crucial role is to help the body process fats.

Probably the most extensively researched benefit of betaine is its use to convert homocysteine in the blood to methionine. Homocysteine is an amino acid that is produced by the body naturally. Amino acids are the building blocks of all the proteins in the body. Although amino acids are critical compounds needed for many body functions, studies show that high levels of the amino acid homocysteine can be harmful to blood vessels, potentially leading to the development of plaque buildup and the condition called atherosclerosis (clogged arteries).(1) (2)

Betaine Deficiency
A betaine deficiency is not thought to be common in western nations, mostly because betaine is present in high amounts in wheat products, which are a staple in most people’s diets. Although it’s not directly due to low betaine intake, diets low in betaine may contribute to high homocysteine in the blood. High homocysteine levels in the blood may be elevated for many reasons, mainly epigeneticsdue to environmental factors, diet and life style.

The biggest threat to consuming low betaine levels is experiencing symptoms related to high homocysteine in the blood. This is seen most often in either older populations above 50, those who have suffered from alcoholism, or in children who have genetic conditions that lead to high homocysteine. Although this condition is rare, severely elevated levels of homocysteine can cause developmental delay, osteoporosis (thin bones), visual abnormalities, formation of blood clots, and narrowing and hardening of blood vessels. (3)

References:

1. Alfthan G, Tapani K, Nissinen K, et al. (2004) The effect of low doses of betaine on plasma homocysteine in healthy volunteers. Br J Nutr.92:665-669.
2. Atkinson W, Elmslie J, Lever M, Chambers ST, George PM (2008). Dietary and supplementary betaine: acute effects on plasma betaine and homocysteine concentrations under standard and postmethionine load conditions in healthy male subjects. Am J ClinNutr87(3):577-585.
3. Angulo P, Lindor KD. Treatment of nonalcoholic fatty liver: present and emerging therapies. Semin Liver Dis. 2001;21(1):81-88.
4. Barak AJ, Beckenhauer HC, Badkhsh S, Tuma DJ. The effect of betaine in reversing alcoholic steatosis. Alcohol ClinExp Res. 1997;21(6):1100-1102.
5. Barak AJ, Beckenhauer HC, Tuma DJ. (1995) Betaine, ethanol, and the liver: a review. Alcohol. 1996; 13(4): 395-398.
6. Boushey CJ, et al. A quantitative assessment of plasma homocysteine as a risk factor for vascular disease. Probable benefits of increasing folic acid intakes. JAMA. Oct 4,; 274(13): 1049-1057.
7. Eikelboom JW, Lonn E, Genest J, Hankey G, Yusuf S. Homocyst(e)ine and cardiovascular disease: a critical review of the epidemiologic evidence. Ann Intern Med. 1999;131:363-375.
8. Hanje AJ, Fortune B, Song M, Hill D, McClain C. The use of selected nutrition supplements and complementary and alternative medicine in liver disease. NutrClinPract. 2006 Jun;21(3):255-272. Review.