Limit Consumption Green Tea During Pregnancy
According to a study published in the March 2005 issue of Cancer Research, ECGC, a catechin present in green tea in amounts about 5 times higher than in black tea, inhibits the enzyme dihydrofolate reductase (DHFR), which cancer cells need to be able to grow, and which is a well recognized target of anti-cancer drugs.
Scientists decided to look at ECGC after they realized the green tea catechin looks a lot like the cancer drug methotrexate, which prevents cancer cells from making DNA by inhibiting the DHFR enzyme. They discovered that ECGC kills cancer cells in the same way as the drug.
Although ECGC binds strongly to DHFR, which is essential in both healthy and cancerous cells, it does not bind as tightly as methotrexate, so its side effects on healthy cells are less severe than those of the drug.
ECGC's binding to DHFR may also explain why women who drink large amounts of green tea around the time they conceive and early in their pregnancy may have an increased risk of having a child with spina bifida or other neural tube disorders.
Women are advised to take supplements of folic acid when trying to conceive and during the first trimester (the first 3 months) of pregnancy because it is during this time period that the baby's neural tube is developing. Folic acid helps ensure normal development and protects against spina bifida by enabling the production of the enzyme DHFR. While a cup or two of green tea is unlikely to pose a problem, drinking large amounts of green tea could decrease the activity of DHFR, increasing risk of neural tube defects.