Green Tea and Breast Cancer Research

Green tea has been in the news a lot lately, with claims that it has benefits for Sjogren’s syndrome, rheumatoid arthritis, infection, helps prevents the formation of blood clots, helps you lose weight, blocks UV rays in your skin, reduces HIV’s ability to infect cells, prevents tooth decay, lowers LDL (bad) cholesterol levels, and even stops cancer from developing. It sounds a little like a description of snake oil to me, so I decided to check it out.

One new benefit that is being researched is the claim that green tea can help prevent breast cancer and to help in fighting the disease. I started my investigation there.

EGCG Polyphenol

Green tea is rich in flavonoids, alkaloids, polyphenols, tannins, and minerals such as fluoride and aluminum. In terms of cancer treatment and prevention, the polyphenols are the most important constituent. Polyphenols are a group of chemicals found in plants, distinguished by the presence of more than one phenol group per molecule.

Polyphenols are further subdivided into tannins, and phenylpropanoids such as lignins and flavonoids. They are natural plant antioxidants.

Green tea has one polyphenol that is considered the best for good health; epigallocatechin gallate (EGCG). EGCG is a catechin flavinoid, and an antioxidant. It has been shown to inhibit cancer cells in animals from reproduction. It also killed cancer cells in test tubes without harming healthy cells surrounding them.

Apparently there is a difference in green tea and black tea. Both come from the Camellia sinensis plant but black tea is fermented and green tea is not. Oolong tea is made from partially fermented tealeaves. Green tea is popular in the nations of the Far East and is becoming more popular throughout the world.

Animal Research

The first research to find a reduction in the size and malignancy of breast tumors from drinking green tea was conducted by researchers at the Boston University Schools of Medicine and Public Health.

Studies were done on rats, and involved green tea. Part of the study group drank green tea and the other half drank only water. The rats that drank green tea had their tumors grow smaller and new tumors were slower in developing. The rats that drank only water had no significant drop of growth in their tumors and developed new tumors faster.

Published in 2007,a more recent study looked at the effect of green tea catechins (GTC) and black tea theaflavins (BTT) on the occurrence of breast cancer in mice. The green tea extract and black tea extracts both decreased the incidence as well as the size of mammary tumors in the subject mice, with green tea being more effective than black tea.

Human Research

Human studies involving green and black tea show an increase in plasma antioxidant capacity 1 hour after consumption of moderate amounts of tea, on the order of 1-6 cups/day. (Rietveld & Wiseman, 2003). A Chinese study of 18,000 men found tea drinkers to be roughly half as likely to develop esophageal or stomach cancers as men who drank little to no tea (Sun et al., 2002).

But on the other hand, a 1996 study in the Netherlands of 58,000 men and 62,000 women ages 55 to 69 showed no link between tea consumption and cancer protection (Goldbohm, Hertog, Brants, van Poppel, & van den Brandt, 1996).

In 2003, a case-control study of breast cancer among Asian women living in California was done, comparing health, diet and lifestyle habits of 501 women with breast cancer to 594 women without the cancer. They concluded “green tea drinkers showed a significantly reduced risk of breast cancer.” and “there was a significant trend of decreasing risk with increasing amount of green tea intake”. Women who drank more than around 3 oz. of green tea a day had a 47% lower risk of developing breast cancer than those who drank no green tea.

And in 2006, a study of more than 40,000 people in Japan showed that although drinking green tea can significantly cut deaths from cardiovascular disease, there was no beneficial effect of consumption of green tea on cancer mortality.

Drink Lots of It

To be effective in humans, one would probably need to consume three to four cups of green tea each day. You would need to drink your tea without sugar and milk. If you are at risk of developing breast cancer you may consider drinking green tea. That may be too much tea to drink each day but there are people who drink more coffee and soda daily.

Another drawback is the caffeine found in green tea. Green tea contains less caffeine than the same amount of coffee but if you are drinking green tea in large quantities, it does add up fast. Caffeine can cause insomnia and interrupt sleep patterns.

Green tea extracts are available in capsule form in health food stores. Remember, though, it hasnt yet been proven to be effective in slowing cancer growth. If you like to drink tea and dont mind caffeine, then check out the tea aisle in your local grocery store. Youll find a large variety of green tea, both in regular and decaffeinated varieties. One good flavor I tried recently was peach flavored green tea. I enjoyed it so much I forgot it contained caffeine and drank a few cups. I wont be doing that again.


As one meta-analysis states,

    “Epidemiologic data has suggested that green tea may prevent breast cancer. Studies in our laboratory have provided evidence that green tea extract inhibits breast cancer growth by a direct anti-proliferative effect on the tumor cells, as well as by indirect suppressive effects on the tumor associated endothelial cells.”

In other words, as a breast cancer preventative, green tea has been shown to at least have some potential benefits. It has also been shown to inhibit cancer cells in the lab. But to say that it can cure breast cancer is clearly a misrepresentation of the current literature.