Genetic effects of Green Tea on Fibroid Growth
Fibroids and Hormones : Risk Factors
Factors which are currently thought to promote growth of fibroids are periods of excess estrogen, periods of unopposed estrogen(when there is insufficient progesterone to balance out estrogens), and xenoestrogens (environmental chemicals such as those found in some plastics or pesticides which mimic the effects of estrogen in the body). Risk factors for fibroids are many, and factors such as having an early age of onset of the menses or lack of ovulation give unopposed estrogen more time to stimulate fibroid growth. Risk of fibroids is reduced by having children (also known as the effects of parity- risk is reduced most for women who have several children) which is now thought to be related to ischemic effects on the uterus after birth (reduced blood flow to the uterine tissues and involution of the uterus) which appear to reduce formation and growth of fibroids. Fibroids are more common in women over 40, and this may be related to changes in hormonal mediators during perimenopause, or alternately from 20-30 consecutive years of exposure to estrogen.
Although it has been traditionally thought that estrogen is the only promoter of fibroid growth, research now points to progesterone as a stimulator of fibroid growth. Fibroids contain both progesterone and estrogen receptors which are up and down regulated during the menstrual cycle. A key to stimulation of fibroid growth may be in conversion enzymes. Studies point to increased expression of an enzyme known as aromatase in women who have fibroids. Aromatase is an enzyme which converts androgens to estrogen (androgens are male hormones, and the precursors to estrogen). This information indicates that treatments which work at the level of this enzymatic activity (such as aromatase inhibitors – to be discussed on a future blog post) can bring more balance to the effects of of estrogen on tissues, especially if started at an early stage of the condition.
Fibroids: The Liver and Diet
Another factor which can cause growth of fibroids relates to the clearance of hormones and conversion of estrogen to weaker forms by the liver. If liver function is poor, more estradiol will circulate and increase growth of the fibroids. Dietary factors which are also linked to risk of fibroids include low fibre diets (fibre improves elimination of hormones). Higher fat and lower fibre diets have also been linked to higher levels of estradiol according to a meta analysis of date from the Journal of the National Cancer institute, and obesity is also correlated with a higher risk for fibroids (androgens are converted to estrogens in adipose tissue). Green tea also has thermogenic (fat burning) effects according to multiple studies (effects beyond that of the caffeine it contains), so it may be helpful for women with fibroids from this standpoint as well.
A study from Japan indicated that green tea and other caffeinated beverages reduced serum estrogen by increasing sex hormone binding globulin, which is also of benefit in reducing the rate of estrogen stimulated fibroid growth. Although other caffeinated beverages such as coffee also appeared to increase sex hormone binding globulin, only green tea was correlated to a day 11 lower serum estradiol.
Although more research is needed in this area before firm conclusions can be drawn on this topic, it seems that EGCG has multiple benefits for women who are at risk for fibroid development. Though unlikely to shrink larger developed fibroids to a great extent, it may have a role to play in earlier stages and in prevention of these benign yet troublesome growths.
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