Flaxseed: A Powerful Cancer-Fighting Food

Flaxseed has an array of dietary uses and it may have health benefits. These seeds have been found to contain components—including phytoestrogens, alphalinolenic acid, and fiber—that may help improve cancer survival for some people. Studies have shown mixed results and more research is needed, but it's something you may want to learn more about.

This article will explore the benefits of flaxseed and flaxseed oil, especially in regards to the effects on cancer.

Flaxseed in a spoon
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Benefits of Flaxseed

Flaxseed is a source of dietary fiber, and fiber often helps relieve constipation. Flaxseed may also be beneficial for your health if you have heart disease, high blood sugar due to type 2 diabetes, or menopausal symptoms. Flaxseed oil may also help relieve dry eyes.

Freshly ground flaxseed typically provides the most nutritional benefits. Whole seeds can pass through the system relatively undigested, and ground seeds exposed to air for prolonged periods of time are subject to oxidation, potentially negating some of their beneficial properties.

You can sprinkle no more than a total of 2 to 3 tablespoons per day on bread, cereals, soups, and salads. You can also add flaxseed oil to salad dressings or mix it with a smoothie.

Due to its high fiber content, it's important to drink plenty of fluids and to increase your flaxseed intake slowly to avoid bloating.

Flaxseed and Cancer

Several studies have been done to determine how the phytoestrogens, which are plant-based estrogen-like compounds in flaxseeds, could play a role in helping cancer.

In animal studies, it has been shown that consumption of flaxseeds may block estrogen receptors on cells within the breast tissue. This has been proposed as a potential mechanism for stopping tumor growth and preventing cell damage.

What Is Flaxseed?

Flaxseeds are about the size of sesame seeds.

Dietary fiber in flaxseeds and flaxseed oil can be beneficial for digestive functions for some people. This gastrointestinal effect can have positive effects beyond digestion. Two components of flaxseeds that have been studied in relation to cancer are lignans (a phytoestrogen) and alphalinolenic acid (ALA).

Dietary Fiber

Freshly ground flaxseeds are a source of dietary fiber. Fiber from flaxseeds may help lower cholesterol and reduce constipation for some people.

The gut microflora (bacteria in your stomach and intestines) can affect everything from our moods to how well cancer treatments work. We've learned that it's possible to change the number and diversity of bacteria in the digestive system through our diets, and flaxseed may have a role in this process.

A diet high in fiber correlates with healthier gut microflora. Fiber, including the fiber in flaxseeds, acts as a prebiotic, feeding the gut bacteria, maintaining beneficial bacteria, and keeping the bad bacteria in check.

Recent studies have found that how well a person responds to cancer immunotherapy treatment is related to a healthy diversity of the gut microflora.


Flaxseeds and sesame seeds are both sources of lignans, a plant-based estrogen.

Lignans may act as a weak estrogen, binding to estrogen receptors on cells in breast and endometrial tissues. This action may protect cells that are susceptible to cancer-associated damage from estrogen exposure.

Alphalinolenic acid (ALA)

Alphalinolenic acid is an omega-3 fatty acid, that is not made in your body—it must come from food. Omega-3 fatty acids are polyunsaturated fats that help reduce inflammation.

When omega-3s are part of a well-balanced diet—which includes vitamin C, vitamin E, beta-carotene, and selenium—the combination of nutrients may help reduce breast cancer-associated inflammation.


If you're taking flaxseed as a laxative, drink plenty of water to avoid constipation or intestinal blockage because the seeds expand during digestion. Your body needs time to absorb the components of flaxseed, so wait a while before taking any other supplements or medications.

Avoid flaxseed oil if you are allergic to flax or if you are pregnant or nursing. Talk with your healthcare provider if you have diabetes or if you're on blood thinners; flaxseed can lower blood sugar and may increase bleeding. If you've had estrogen-receptor-positive breast cancer, check with your doctor before using flaxseed products.

Dietary Tips

You can add flaxseed to muffins, cookies, add ground flaxseed to cereal, yogurt, or a smoothie.

Sometimes flaxseed has a distinct taste that may be a little bitter, especially in baked goods. Adding flavors like banana, chocolate chip, cinnamon, and cranberry-orange can help with this.


Flaxseed is a small dietary ingredient, but it contains many chemicals and properties that may help improve health. Research studies are examining whether it could potentially help fight cancer. Before adding it to your diet, talk with your healthcare provider. Flaxseed should not be used as a replacement for any medication or treatment, and it may have negative effects for some people.

Frequently Asked Questions

  • What is flaxseed good for?

    Flaxseed may help with gut health and weight loss because of its high fiber content; it also might help relieve constipation for some people. It may have beneficial effects on heart health and blood pressure.

  • How much flaxseed should you have per day?

    There is no official recommendation for daily intake. No more than 1 to 2 tablespoons is a generally accepted healthy daily amount.

  • Who should not eat flaxseed?

    You should not use flaxseed if you are pregnant or nursing. Flaxseed may interfere with bleeding and blood sugar levels so if you have diabetes or a bleeding disorder, be sure to talk with your healthcare provider about whether flaxseed is safe for you to take. Before anyone starts incorporating flaxseed into their diet, checking with your healthcare provider is always a good idea.

  • Is flaxseed good for estrogen-positive breast cancer?

    The possible benefits are being studied because flaxseed contains lignans. Certain components of lignans have antiestrogen properties and may also reduce cancer cell growth. Animal studies have found a combination of tamoxifen and flaxseed can shrink tumor size more than just tamoxifen alone.

6 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. American Institute for Cancer Research. Flaxseed: full of fiber and phytochemicals.

  2. National Center for Complementary and Integrative Health. Flaxseed and flaxseed oil.

  3. Calado A, Neves PM, Santos T, Ravasco P. The effect of flaxseed in breast cancer: a literature review. Front Nutr. 2018;5(4). doi:10.3389/fnut.2018.00004

  4. Liu K, Lu C. Gut microbes modulate host response to immune checkpoint cancer immunotherapy. Translational Cancer Research. 2018;7(Suppl 5):S608-S610. doi:10.21037/tcr.2018.05.37

  5. Freitas RDS, Campos MM. Protective effects of omega-3 fatty acids in cancer-related complications. Nutrients. 2019;11(5):945. doi:10.3390/nu11050945

  6. Rajavi SD, Samy KK. Flax seed and climacteric symptoms - a review. Journal of Evolution of Medical and Dental Sciences.

Originally written by Pam Stephan
Pam Stephan is a breast cancer survivor.
Learn about our editorial process