Hormone imbalance from evening primrose oil?

The estrogen connection

This is an update to my post on evening primrose oil. A comment left by Ann about her aunt gave me some concern and I decided to run more research into the topic. Apparently, her aunt was diagnosed with breast cancer and according to her doctor, the food she ate – namely, evening primrose oil and bean curd (douhua) – may have contributed to that.

I couldn’t find any information regarding the disadvantages of taking evening primrose oil at first and many people I spoke to also told me that it is suppose to benefit women. It was not until I talked to a colleague about Ann’s aunt that she linked the connection between soy and estrogen and that led me to discover that evening primrose oil also has estrogenic properties – although some sources dispute that.

Usage of evening primrose oil may cause problems for some
According to various sources I’ve read, including this, while evening primrose oil alleviates PMS, long term use may actually aggrevate the problems and it seems, most people don’t realize this.  I certainly didn’t!

However, the problems may not be across the board as estrogens are present in almost every type of food that we eat.   It might have to do with a person’s state of health too and since the liver is the organ that removes estrogens, someone with a weak liver may fail to remove estrogens efficiently and hence, lead to their accumulation. When excessive estrogens become trapped in the uterus, ovary, or breast due to stagnation, they overstimulate cell division and lead to abnormal growth such as fibroids, cysts or cancer in these organs. (source)

Soy produces weak estrogens
Soy, on the other hand, have shown many benefits in providing relief for menopause symptoms.  So soy foods, like tofu, contain phytoestrogens, specifically the isoflavones, genistein and diadzein are always said to be beneficial. In a woman’s body, these compounds can dock at estrogen receptors and act like very, very weak estrogens. During perimenopause, when a woman’s estrogen fluctuates, rising to very high levels and then dropping below normal, soy’s phytoestrogens can help her maintain balance, blocking out estrogen when levels rise excessively high, plus filling in for estrogen when levels are low. (source: WHFoods)

soy supplement
Soy supplements not recommended for all
So it looks like  soy isoflavones can provide benefit in reducing the risk of cancer.  In fact, for women who are taking HRT, which comes with an increased risk of certain cancers such as breast cancer, soy isoflavones could possibly provide an additional protective effect.  However, registered dietician Leslie Beck, who is also author of the book Managing Menopause, was quoted in a CBC News article to caution any woman with a family history of breast cancer against taking soy supplement.  “Soy in food a couple of times a week, no problem…In post-menopausal women we’re not sure if soy might act as an estrogen promoter. It acts differently in pre-menopausal women than in post-menopausal.”

A case of estrogen dominance
I’m not trying to be a scare monger here but since I’ve written about the benefits of evening primrose oil, I feel that I have a responsibility to clarify now that I’ve found some new info.  In addition, I was mildly concerned about my menstrual flow for this month and I wonder if taking the evening primrose oil had tipped my cycle the other way round.   It could have contributed to a case of estrogen dominance, causing even more hormonal imbalance for me.

Take everything in moderation
So, I’ll like to state that it’s best to take this in moderation and if you have a family history of breast cancer, you want to be even more cautious.   Of course, the link between estrogen and breast cancer isn’t as straightforward as it involves DNA mutation in cells and hence, isn’t across the board for all.   If you’re interested to find out more, National Cancer Institute has some slides explaining the link.


  1. Marti B. says:

    Omg!! Ive been taking EPO for about 2months every other day!
    It has made me sad all the time, suddenly ultra sensitive, moody, & a profuse sweater!!!
    Not to mention I’m on my SECOND PERIOD for this month! I thought this would aide me in the fertility department. But I’m not willing to continue taking them to see!

  2. Iona says:

    I took a low level 1 a day evening primrose oil supplement I bought in the supermarket and after 2 / 3 months my breasts had enlarged which was great for me but my menstral bleeding was all over the place. So even though having larger breasts was a definite bonus I had to stop taking it to get my cycle regular again.

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