Epigallocatechin gallate (EGCG) inhibits the dihydrofolate reductase (DHFR) enzyme.
- The antifolate activity of tea catechins.
Binding of natural and synthetic polyphenols to human dihydrofolate reductase.
EGCG also inhibits the absorption of dietary folate.
- Effect of epigallocatechin gallate on drug transport mediated by the proton-coupled folate transporter.
DHFR lies at the beginning of the biochemical pathway for processing dietary folate into the form known as 5-methyltetrahydrofolate (more commonly known as methylfolate). Methylfolate is used to regenerate spent B12 by transfer of a methyl group regenerating active methylcobalamin.
Chronic consumption of green tea, or EGCG supplements, may drive folate levels down into the deficiency range. This in turn can prevent the remethylation of cobalamin and lead to a vitamin B12 deficiency. A deficiency in vitamin B12 can cause neurological damage known as subacute combined degeneration. This disease is characterized by demyelination of the spinal chord. It is a particularly disabling condition.
- Please see the videos at...
and also the images at
http://radiopaedia.org/articles/subacut ... the-cord-1
Susceptibility to subacute combined degeneration induced by folate deficiency from EGCG consumption is increased in individuals who have single nucleotide polymorphism (SNP) defects in the methylenetetrahydrofolate reductase (MTHFR) enzyme. The heterozygous 677C>T SNP reduces the MTHFR function by about 40% and the homozygous 677C>T SNP decreases the function of the MTHFR enzyme by about 70%.
The prevalence of the homozygous 677C>T SNP is increased in populations of Italian and Hispanic descent.
- Geographical and ethnic variation of the 677C>T allele of 5,10 methylenetetrahydrofolate reductase (MTHFR): findings from over 7000 newborns from 16 areas world wide.
http://www.ncbi.nlm.nih.gov/pmc/article ... p00619.pdf
There's probably no coincidence in the observation that the Italians are not known for drinking green tea.
In the end, green tea has many healthy benefits. HOWEVER, if you're a carrier of the MTHFR SNPs, then you may be putting your health at great risk. If you're going to drink green tea at therapeutic levels, e.g., 3-4 cups/day, or take EGCG supplements, then it might be best to have regular, e.g., biannual, testing of B12, folate and homocysteine (the latter of which is a cardiotoxic amino acid that builds up when either B12, B6 or folate is low and is associated with increased risk of heart attack, stroke, hypertension and irregular heartbeat).