Healthy Pregnancy Concerns Over Green Tea
Pregnant women would be wise to limit the amount of green tea
they drink during pregnancy, and should be careful about taking
any green tea supplements. Green tea is rich in antioxidants,
and has a host of health benefits relating to dental health,
blood sugar levels, cholesterol, and weight loss. But
researchers have found, whilst examining the active constituent
of green tea, the epigallocatechins, or EGCG for short, that it
may affect the way the body uses folate. Folate is important for
pregnant women as it prevents neural tube birth defects in
babies.
The problem of green tea during pregnancy is that the EGCG
molecules are structurally similar to a compound called
methotrexate. Methotrexate is able to kill cancer cells by
chemically bonding with an enzyme in the body called enzyme
dihydrofolate reductase (DHFR). Healthy people have this enzyme
also - it is part of what is called the folate pathway, which is
the pathway, or steps, the body takes to transform nutrients
like folate into something that can be used to support its
normal functions.
But this chemical similarity means that the EGCG in green tea
also binds with the enzyme DHFR, and when it does this, it
inactivates this enzyme. When this enzyme is inactivated, the
ability of the body to use folate is going to be affected. How
much green tea is able to be consumed, or precisely how much
folate absorption is affected, is unclear. Though the research
article did say that drinking 2 cups of green tea a day can stop
cancer cells (which is what methotrexate is targeting) from
growing.
The good news on caffeine drank during pregnancy, from coffee
and tea, is that a moderate amount is fine. Two studies, one by
Danish scientists who interviewed more than 88,000 pregnant
women, and the other by the Yale University School of Medicine,
had similar findings on caffeine during pregnancy.
The concerns over caffeine were that it would lead to low birth
weight or miscarriage. And this is still true of a very high
daily intake of coffee. The Yale team found that drinking about
600mg of caffeine a day, which is about 6 cups of coffee, would
reduce birth weight to levels that were clinically significant.
The rate at which birth weight was reduced was established at
being 28 grams per 100 mg, or 1 cup, of coffee per day. But they
emphasized that this would not be significant for moderate
caffeine consumption.
The Danish study found that drinking 8 cups or more of coffee
per day (this would be about 16 cups or more of tea), would
increase the chances of miscarriage, or stillbirth, by 60%
compared to women who did not drink caffeine. They also found
that moderate coffee or tea drinking did not pose significant
risks. For those drinking half a cup to 3 cups of coffee a day,
the risk of fetal death was 3% higher compared to non-caffeine
drinkers. And for those drinking 4 to 7 cups of coffee a day,
the risk increases to 33%. One cup of coffee equals about 2 cups
of tea when comparing caffeine levels. The recommended amount of
coffee drunk is up to 3 cups daily, or 6 cups of tea, by the UK
food agency.
References:
http://www.nutraingredients-usa.com/news/ng.asp?id=58807
http://www.nutraingredients-usa.com/news/ng.asp?id=24747
http://www.foodnavigator.com/news/ng.asp?id=63174