The difference between green and black teas is in the processing. Green tea is made by steaming and drying the tea leaves which allows for compounds known as "polyphenols" to be preserved. The polyphenols, most especially the catechins, are powerful antioxidants, and may be the compounds that give green tea its purported health benefits. In contrast, black tea is fermented during processing, reducing the ability of polyphenols to act as antioxidants. Green tea is available with caffeine or may be decaffeinated.
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.
Many pregnant women carefully avoid caffeine, alcohol, nicotine, and unnecessary medications but think nothing of drinking cup after cup of herbal tea. If this sounds like you, take heed: Herbal teas can be harmful, especially if you drink too much of them. Most of the ingredients in herbal teas are safe, but many are not. Herbs are drugs and thus can be as potent as some medications. What's more, only a few of the herbs used for teas have been studied in pregnant women.
These two substances can turn up in unexpected places, like a liqueur-filled truffle or coffee ice cream. And be aware that chocolate is also high in caffeine, so watch that sweet tooth. Caffeine and alcohol actually prevent absorption of folic acid and iron – two essential nutrients during pregnancy – and pull calcium out of your bones, not to mention that they also directly affect the fetus and can have long-term developmental effects.
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.
Caffeine crosses the placenta to your baby. Although you may be able to handle the amounts of caffeine you feed your body, your baby cannot. Your baby's metabolism is still maturing and cannot fully metabolize the caffeine. Any amount of caffeine can also cause changes in your baby's sleep pattern or normal movement pattern in the later stages of pregnancy. Remember, caffeine is a stimulant and can keep both you and your baby awake.
There are a number of teas labeled as “Pregnancy Teas”, or herbs such as red raspberry leaf that are in teas, that are considered to be good for pregnancy. Many midwives and professionals who work with herbs believe that the regular consumption of these teas may help prevent pregnancy complications such as preeclampsia, preterm labor, prolonged labors, and postpartum hemorrhage.
If you are pregnant or thinking of becoming pregnant, make a list of foods you normally eat and get them cleared with your doctor. Be especially prudent about any vitamins, herbs, or supplements you are taking and bring them in the office at your earliest opportunity.
