Green Tea in pregnancy and breastfeeding

What NCCIH says about safety

No safety concerns have been reported for green tea consumed as a beverage by adults. However, green tea does contain caffeine. Side effects of green tea extract supplements include nausea, constipation, abdominal discomfort, and increased blood pressure. Although uncommon, liver injury has been reported in some people who used green tea products, primarily green tea extracts in tablet or capsule form. Individuals with a specific variant of a gene that plays an important role in immune function appear to be especially susceptible. Between 5 and 15 percent of Americans have this variant. Green tea at high doses has been shown to reduce blood levels and, therefore, the effectiveness of the drug nadolol, a beta-blocker used for high blood pressure and heart problems. Green tea extract can reduce blood levels of the cholesterol-lowering drug atorvastatin. A study funded by the National Center for Complementary and Integrative Health showed an interaction between green tea and the drug raloxifene, which is used to treat osteoporosis. Green tea may also interact with other medicines. If you take any type of medicine, talk with your health care provider before using green tea supplements or other herbal products; some herbs and medicines interact in harmful ways. During pregnancy, caffeine intake should not exceed moderate levels. Green tea is a source of caffeine. If you are or might be pregnant, consult your health care provider for advice about caffeine intake. Caffeine can pass to your infant through breast milk; if you consume high levels of caffeine, it can lead to symptoms such as fussiness and poor sleep patterns in your infant. However, breastfeeding infants usually do not have adverse effects when mothers consume low-to-moderate levels of caffeine.

Quoted in full from NCCIH so nothing is lost in summarising. Where they say “little is known”, that means the studies do not exist — not that the herb is known to be safe, and not that it is known to be harmful.

How much is actually known

Although many studies have been done on green tea and its extracts, definite conclusions cannot yet be reached on whether green tea is helpful for most of the purposes for which it is used.

What the research has found

The FDA has approved a specific green tea extract ointment as a prescription drug for treating genital warts. Many studies have looked at the relationship between green tea consumption and the risk of various types of cancer. The overall results of these studies have been inconsistent. In Asian populations but not in Western populations, green tea consumption has been linked to a lower risk of coronary heart disease. The catechins and caffeine in green tea and its extracts may have a modest effect on body weight. However, the effects of green tea products may vary depending on the composition of the product and the individual’s level of physical activity. The effect of green tea on blood cholesterol levels has been tested in studies in which people were randomly assigned to consume either a green tea product or a placebo. Most of the studies evaluated green tea extract supplements rather than green tea as a beverage. Green tea reduced total cholesterol and low-density lipoprotein (LDL) cholesterol to a small extent, but it did not affect high-density lipoprotein (HDL) cholesterol or triglycerides.

Before you take this

Dose and form change the answer completely. A culinary amount of a spice, a cup of tea, and a concentrated supplement extract are three different things, and most research is done on the last of them.

Supplements are also not regulated like medicines, so strength and purity vary between products. Bring the actual bottle to your midwife, doctor or pharmacist — that conversation is worth more than any page, including this one.