Biological and clinical implications of the MTHFR C677T polymorphism

Trends Pharmacol Sci. 2001 Apr;22(4):195-201. doi: 10.1016/s0165-6147(00)01675-8.


The enzyme methylenetetrahydrofolate reductase (MTHFR) directs folate species either to DNA synthesis or to homocysteine (Hcy) remethylation. The common MTHFR C677T polymorphism affects the activity of the enzyme and hence folate distribution. Under conditions of impaired folate status, the homozygous TT genotype has been regarded as harmful because it is associated with a high concentration of plasma total Hcy, increased risk of neural tube defects and colorectal neoplasias, and can also predispose individuals to adverse effects from drugs with antifolate effects. The MTHFR C677T polymorphism shows no consistent correlation with cardiovascular risk and longevity but, in combination with positive folate balance, the TT genotype is associated with decreased risk of colorectal neoplasias. Because of the high prevalence of this polymorphism in most populations, the TT variant might represent an ancestral genetic adaptation to living constraints (tissue injury or unbalanced vitamin intake) that has become a determinant of disease profiles in modern times.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Cardiovascular Diseases / enzymology
  • Cardiovascular Diseases / genetics
  • Folic Acid / metabolism*
  • Genotype
  • Humans
  • Kidney Diseases / enzymology
  • Kidney Diseases / genetics
  • Methylenetetrahydrofolate Reductase (NADPH2)
  • Oxidoreductases Acting on CH-NH Group Donors* / genetics
  • Oxidoreductases Acting on CH-NH Group Donors* / metabolism
  • Oxidoreductases Acting on CH-NH Group Donors* / physiology
  • Polymorphism, Genetic*
  • Risk Factors


  • Folic Acid
  • Oxidoreductases Acting on CH-NH Group Donors
  • Methylenetetrahydrofolate Reductase (NADPH2)