Ask the Nutritionist
Q: I have ovarian cancer that is more that 75% estrogen sensitive. Do sweet potatoes, yams and flax seed mimic estrogen, and should I avoid these foods?
Sandy P., Southington, CT
A: There are two types of yams, and each has very different properties. The first type, also called a "true yam," is the root vegetable you can buy at the supermarket. It's a member of the sweet potato family. These types of yams are not associated with estrogen activity.
We suggest keeping these vegetables as a part of your diet. Sweet potatoes are high in vitamin A, which sustains healthy vision, bone growth, and immune systems. They also contain vitamin C, which supports wound healing, hair growth, and tissue repair.
The second type of yam is called "wild yam" or China root, black yam, Mexican yam, white yam, wild yam root, and yuma. This is a supplement that does not contain any natural sex hormones. While there have been rumors that wild yam acts as a precursor to sex hormones like estrogen or progesterone, that transformation has never been clinically proven.
While wild yam does not naturally contain sex or reproductive hormones, the FDA does not regulate chemically made supplements. As a result, it is possible that wild yam products (including creams) may be tainted with added artificial progesterone, and should be avoided.
The reputation of flaxseed as a cancer promoter or preventer is still being debated. It is an excellent source of omega-3 fatty acids, but the seed (not the oil) is an antioxidant with possible estrogen receptor activity. There is not enough evidence to recommend whether people should stop eating flaxseeds or eat more of them.
Because the research on flaxseed's effect on estrogen is inconclusive, The National Institutes of Health advises someone with a hormone- sensitive condition such as yours to avoid flaxseed. They report that, "due to the possible estrogen-like effects of flaxseed (not flaxseed oil), it should be used cautiously in women with hormone-sensitive conditions, such as endometriosis, polycystic ovary syndrome, uterine fibroids, or cancer of the breast, uterus, or ovary."
Additionally, flaxseeds may increase the effects of tamoxifen, a cancer-fighting drug.
You can consume pure flaxseed oil if you choose. The oil, which is stripped of the woody shell that contains the fiber as well as possible anti-cancer and antioxidant compounds, is still a good source of alpha linoleic acid (ALA), which may have cholesterol-lowering properties.