Folic acid is important for human health due to its role in methylation biochemical process. Methylation indicated that the -CHS was carried on the cytosine by DNA methyltransferase and turned into 5-mC, which happened the 5’CpG island frequently.

L-5-methylenetetrahydrofolate(L-5-MTHF) is the metabolic product of folic acid in human body. And it is also the folic acid form which has strongest bio-activity and function. Only after transfer into L-5-MTHF, folic acid can take part in methylation and DNA synthesis. (Melikian, 1971)

L-5-MTHF participate in many essential biochemical reaction such as the synthesis of purine and thymine. It can be used directly without complex enzymatic process. 

The exuberant metabolism is caused by rapid cell reproduction in pregnant period and lactation. The supplement of folic acid is able to significantly prevent the neural tube defects in infants.(Cathrine, 2011)

In addition, L-5-MTHF has effect on treatment of arteriosclerosis and erythrocyte anemia.

1. On the function of DNA synthesis and DNA repair.

On the function of DNA synthesis and DNA repair. L-5-MTHF and its status are related to children with leukemia, colon cancer and breast cancer. It is called cervical atypical hyperplesin before precancerous lesions. From a smoker study, high dose folic acid and vitamin B12 can reverse the changes of pre lung cancer.(Ito, 2005)

There is a great importance of L-5-MTHF to gene expression of L-5-MTHF. Methyl group(provided indirectly by L-5-MTHF) should’t activate the certain gene in a certain period. It is the key to health. Some genes in human body are cancer promoters. Proper methylation needs L-5-MTHF which can silence these genes. When there is lack of L-5-MTHF, these cancer genes become dynamic, which has negative effects.

2. Detoxify harmful compound

 L-5-MTHF can also detoxify harmful compound such as environmental toxins(Hg, Pb, As), drugs and human hormones. (Widjaja, 2014) Like blood cholesterol, serum levels of homocysteine are directly associated with cardiovascular disease. In recent study o people who had their atherosclerotic(clogged) coronary arteries treated by balloon angioplasty, homocysteine levels were measured. Half of the study participants were supplemented with folic acid and vitamins B6 and B12. At the end of the study, homocysteine levels and coronary artery clogging were again evaluated. The groups that received folic acid, B6 and B12 had lower homocysteine levels and less blood vessel clogging. High homocysteine levels do more than damage arteries.

Conditions associated with elevated homocysteine levels include coronary artery disease, heart attack, stroke, deep vein thrombosis, peripheral vascular disease, miscarriage, birth defects, depression, sensorineural hearing loss, osteoporosis, cancer, arthritis, dementia and complications of diabetes.

Reference

Cathrine Hoyo, Murtha A P, Schildkraut J M, et al. > > > Methylation variation at differentially methylated regions and maternal folic acid use before and during pregnancy[J]. Epigenetics Official Journal of the Dna Methylation Society, 2011, 6(7):928-36.

Ito Y, Wakai K, Suzuki K, et al. Lung cancer mortality and serum levels of carotenoids, retinol, tocopherols, and folic acid in men and women: a case-control study nested in the JACC Study.[J]. Journal of Epidemiology, 2005, 15(2):140-149.

Melikian V, Paton A, Leeming R J, et al. SITE OF REDUCTION AND METHYLATION OF FOLIC ACID IN MAN[J]. Lancet, 1971, 2(7731):955-7.

Widjaja F. Biomarkers in Autism[J]. Frontiers in Psychiatry, 2014, 5:100.