Can women with breast cancer eat flaxseed and soy?

We had another great question on Facebook the other day. Bonnie asked whether women with breast cancer can eat flaxseed. She was worried about the estrogen in the food.

This is a good question because it seems like concerns about flaxseed and even soy won't go away. It's a very controversial subject wrapped around the isoflavones in both of these foods. Isoflavones are considered phytoestrogens, which are weak plant estrogens. And some researchers believe these plant estrogens can encourage hormone-related cancers, such as breast and prostate cancers.

Breast cancer is clearly estrogen driven. So I understand why there's concern. However, there's also clear evidence that dietary phytoestrogens actually reduce your risk for cancer. A Dutch study evaluated 383 women with breast cancer. Of these, 296 were postmenopausal and 87 were premenopausal. The researchers measured their plasma isoflavones. Then they compared their levels to 383 matched controls. Here's what they found:

Women in the highest third of genistein (a particular isoflavone) had nearly a one-third reduced risk of developing breast cancer. In other words, not only did the isoflavones not cause cancer, they helped fight it. How can this be? Shouldn't the plant estrogens at least encourage the cancer? Maybe not.

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It's possible the isoflavones displace the more active cancer-inducing estrogens, such as those from estrogen-like pesticides, in the vulnerable cell receptors. If the body absorbs the healthy estrogen instead of the harmful estrogen, it's possible the result would be less breast cancer. This could be the reason it reduces your risk.

It makes sense. In case you didn't know this, coffee has isoflavones in it as well. But other research has shown that drinking a lot of coffee (five cups daily) can reduce breast cancer by 20%.

In fact, there's far more evidence to suggest flaxseeds, soy, and coffee are not cancer causing and may have anticancer effects. This is true even for ER+ breast cancer. Like soy, the phytoestrogens in flaxseed seem to be more protective against hormone-related cancers.

With that said, the evidence isn't 100% conclusive. That's why there's so much controversy. So talk to your doctor before making big changes to your diet. Keep the intake of flaxseeds moderate – no more than two or three tablespoons daily (or less). I also don't recommend overindulging in soy and coffee either.

Your insider for better health,

Steve Kroening, ND

Sources:

https://www.oncologynutrition.org/erfc/hot-topics/flaxseeds-and-breast-cancer/