Two wooden scoops hold flaxseed.
Eating crushed flaxseed—as opposed to the whole seed—can improve absorption of lignans, which contain phytoestrogens. (For Spectrum Health Beat)

Patients with some types of cancer may want to consider incorporating more soy and flaxseed into their diet.

Why? Because these are two important sources of plant-based estrogen known as phytoestrogen.

While some patients may find themselves overwhelmed at the sheer volume of research available on the topic of phytoestrogens, it’s important to keep in mind it’s not as complex as it seems.

As with most things relating to your health, your dietitian or your health care provider are often your best sources for information.

Dietitians are often asked if flaxseed and soy are safe for people to consume when they have hormone-related cancers such as estrogen-positive breast cancer, uterine (endometrial) cancer or ovarian cancer.

The current consensus among health professionals: soy and flaxseed are indeed safe for patients battling these types of cancer, according to the Oncology Nutrition Dietetics Practice Group.

According to the American Institute of Cancer Research, ground flaxseed may decrease cell growth, increase the destruction of abnormal cells and change estrogen metabolism so that it’s less cancer-promoting.

If you’re curious about the term phytoestrogens, meanwhile, there is a short and easy answer: It’s a type of estrogen derived from plants.

One type of phytoestrogen, isoflavones, are a soy nutrient with a chemical structure similar to the estrogen found in a woman’s body.

Female estrogens, however, are not the same as phytoestrogens.

Crush it

Like flaxseed? Crush it, grind it or mill it to get the best benefits.

According to the Oncology Nutrition Dietetics Practice Group, consumption of crushed or milled flaxseed can increase the absorption of lignans anywhere from 28 to 43 percent. Absorption of the alpha-linolenic acid—a type of omega-3 fatty acid—is reduced when eating the whole flaxseed.

One note of caution: When consuming the whole flaxseed or flax oil, you may experience significant gastrointestinal side effects, including bloating or discomfort. You may want to stick to the ground, crushed or milled variety.

If you’re a woman who enjoys soy, you should set your sights on whole foods such as tofu, soy milk, edamame or soy nuts. You should also follow a more plant-based diet that features fewer processed foods, although the occasional soy protein bar or snack food is OK.

Dietitians and researchers have long known that a plant-based diet abundant in whole foods—anything unprocessed—is the best tool for cancer prevention. These include non-starchy vegetables such as spinach and kale, and then fruit, whole grains and beans.

Flaxseed, meanwhile, is the richest dietary source of lignans and a great source of fiber. It’s safe for people with a history of hormone-related cancers such as estrogen-positive breast cancer, uterine (endometrial) cancer or ovarian cancer.

The lignans in flaxseed can change estrogen metabolism, which can have beneficial effects. In women who have gone through menopause, for example, these lignans can lead to the body making less active forms of estrogen, which is believed to potentially reduce the risk of breast cancer.

The bottom line: Soy and flaxseed are important sources of phytoestrogens that you won’t find anywhere else in such abundant quantities.

You can make them part of your healthy diet, even if you’re battling hormone-related cancers.

Consult your health care provider before starting daily flaxseed if you’re taking fish oil or EPA and DHA supplements or anticoagulant medicine. If you’re currently being treated for cancer, discuss potential use of flaxseed and soy with your registered dietitian.