Methionine

Methionine

What is it?

• Methionine is a key amino acid needed for proper growth and maturation. It helps with metabolism and stress resistance by acting as a precursor for the pathways.

How does it work in the body?

• Methionine cycle: Methionine and ATP produce S-adenosyl methionine (SAM). SAM acts as a methyl donor to molecules allowing for the production of S-adenosylhomocysteine (SAH). It is important that there are low levels of SAH in the cells and, therefore, S-adenosylhomocysteine hydrolase (SAHH/AHCY) breaks it apart. The breakdown of SAH forms adenosine and L-homocysteine. Homocysteine can then be remethylated to form methionine. Adequate functioning of the methionine cycle allows for proper growth and development.

• Transsulfuration pathway: Cysteine can be produced in the liver through the transsulfuration pathway by using the by-product of the methionine cycle, homocysteine. Cysteine is used for the production of certain proteins. An important by-product of this pathway is H.S which has many important functions. H.S can act as an antioxidant agent and helps to control inflammation, insulin release, neural communication, and muscle relaxation.

• Salvage cycle: Polyamines are produced from the regeneration of methionine from SAM. As one ages, polyamine levels are lower [53].

Dosage:

• Methionine can be used for adults to increase acid in urine [54]:

  Capsules: -200 mg 3-4x/day.

  Tablets: 500 mg 3-4x/day.

What is it used for?

• Methionine can be used for the development and maintenance of lean body mass [55].

Safety concerns, side effects, and precautions:

• Methionine is a precursor for homocysteine; therefore, excessive supplemen-tation can lead to hyperhomocysteinemia which can put one at an increased risk for cardiovascular disease [55].

Medication interactions:

• Methionine can decrease the effectiveness of levodopa; therefore, high doses of methionine should be avoided when taking the medication. If taken together, closely monitor for worsening clinical presentation and adjust dose as necessary [56].

Evidence for or against its different uses:

• Human studies are limited on the effects of methionine supplementation. Most studies involving various animals are inconclusive on the effects of methionine supplementation. One study conducted on poultry concluded that the supplementation of methionine improved growth.