Flaxseed: A Powerful Cancer-Fighting Food

Flaxseed has an array of uses and health benefits. Flaxseeds 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 used as a natural laxative, a source of dietary fiber, and to help lower cholesterol.

Flaxseed may also be beneficial for your health if you have heart disease, osteoporosis, breast cancer, and endometrial cancer.

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, drink plenty of fluids, and you should 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?

We've been talking about all the benefits of flaxseed, but what exactly is it? Flaxseeds are about the size of sesame seeds. The two components of flaxseeds that have been studied in relation to cancer are lignans (a phytoestrogen) and alphalinolenic acid (ALA).

Additionally, 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.

Dietary Fiber

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

With the relatively recent awareness that gut microflora (bacteria in your stomach and intestines) can affect everything from our moods to how well cancer treatments work, flaxseed scores a win. We've learned that it's possible to change the number and diversity of bacteria in the digestive system through our diets.

A diet high in fiber correlates with healthier gut microfloria. 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 great 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, as 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, use flaxseed products in moderation.

Dietary Tips

Sometimes flaxseed has a distinct taste to it, especially in baked goods, that may be a little bitter. Adding flavors like banana, chocolate chip, cinnamon, and cranberry orange can help with this. You can add flaxseed to muffins, cookies, add ground flaxseed to cereal, yogurt, or a smoothie.


Flaxseed may be a (literally) small dietary ingredient, but it contains many chemicals and properties that can help improve health and even potentially help fight cancer. Its antioxidants and anti-inflammatory actions make it a powerhouse addition to many foods. Before adding it to your diet in any way, though, talk with your healthcare provider. It should not be used as a replacement for any medication or treatment, and may have negative effects for some people.

Frequently Asked Questions

  • What is flaxseed good for?

    Flaxseed can help with gut health and weight loss because of its high fiber content; it also helps to relieve constipation. It may help with relieving inflammation, as well as have beneficial effects on heart health because of its cholesterol-lowering effects.

  • How much flaxseed should you have per day?

    There is no official recommendation for daily intake. However, 1 to 2 tablespoons is a generally accepted healthy daily amount.

  • Who should not eat flaxseed?

    Those on diabetes medications and those who have bleeding disorders should talk with their healthcare provider about whether flaxseed is safe to take. It may interfere with bleeding and blood sugar levels. 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?

    Yes, it is. It contains lignans. Certain components of lignans have antiestrogen properties. They may also reduce cancer cell size and growth. When taken with tamoxifen, one study found it can shrink tumor size more than just tamoxifen alone.

Originally written by
Pam Stephan
Pam Stephan is a breast cancer survivor.
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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.