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WCRF/AICR
Global Network

AICR HealthTalk

Karen Collins, MS, RDN, CDN, FAND
American Institute for Cancer Research

Q: I’ve heard that flaxseed can help lower blood cholesterol, but I’m worried that it could pose breast cancer risk. What does current research say about this?

FlaxseedA: The latest research shows that consuming flaxseed does not increase risk for breast cancer. At one time, there was concern that flaxseed’s lignans, classified as phytoestrogens could raise the risk of breast cancers that are fueled by high levels of estrogen. Now studies show that although lignans’ chemical structure is like estrogen, they don’t act like estrogen in the body. In fact, research indicates flaxseed may be protective, especially in post-menopausal women. It seems to decrease cell growth, increase self-destruction of abnormal cells and shift estrogen metabolism to less cancer-promoting forms.

As for heart health benefits, some studies do show that including four level tablespoons of ground flaxseed daily may lower LDL (bad) cholesterol and blood pressure, although we need more research to understand who benefits and how much is needed.

Flaxseed does provide other valuable nutrients: it is concentrated in dietary fiber and contains the plant form of omega-3 fat known as ALA (alpha-linolenic acid). An additional benefit –bacteria in our gut convert flaxseed’s lignans into compounds with antioxidant effects.

Do check with your doctor before beginning daily flaxseed if you take fish oil or EPA + DHA supplements or anticoagulant medicine. Also, if you are undergoing cancer treatment, discuss potential use with your care providers. If you take any prescription or non-prescription medicine, be sure to take flaxseed one hour before or two hours after to avoid blocking absorption of the medicine.  Finally, if you’re considering daily flaxseed, note that four tablespoons of ground flaxseed contain about 150 calories.  Substitute it for some other food to avoid undesired weight gain, which would raise risk of both heart disease and cancer.

For more on flaxseed, see our Foods that Fight Cancer.


The American Institute for Cancer Research (AICR) is the cancer charity that fosters research on the relationship of nutrition, physical activity and weight management to cancer risk, interprets the scientific literature and educates the public about the results. It has contributed over $105 million for innovative research conducted at universities, hospitals and research centers across the country. AICR has published two landmark reports that interpret the accumulated research in the field, and is committed to a process of continuous review. AICR also provides a wide range of educational programs to help millions of Americans learn to make dietary changes for lower cancer risk. AICR is a member of the World Cancer Research Fund International (WCRF).

Published on 07/13/2015

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