Flaxseed and Cancer Survivorship
Flaxseed is rich in fiber, magnesium, thiamin and fiber. It is especially of interest as a source of lignans (natural plant compounds found in several plant foods, but concentrated in flaxseed) and a form of omega-3 fatty acids. Flaxseed gets a lot of attention because of stories that say it may increase risk for some cancers and lower risk for other cancers.
Overall research shows there is no sound evidence that flaxseed harms survivors. And for cancer protection, the latest research from AICR found that foods containing dietary fiber, like flaxseed, lower risk for colorectal cancer.
What Research Shows for Cancer Survivors
Most research has focused on flaxseed's effects on breast cancer, but scientists are also studying its impact on prostate and colon cancers.
Breast Cancer Survivors: Lignans form compounds that have a chemical structure similar to estrogen, and in cell studies they seemed to act in ways that mimic estrogen. Earlier, there was concern that flaxseed could increase risk for breast cancer since estrogen-receptor breast cancers grow in response to high levels of the hormone estrogen. However, studies in animals and humans do not support the fears that flaxseed could increase incidence or recurrence of breast cancer. It might even offer protective benefits, but we need more studies to clarify that possibility.
Prostate Cancer: The research is not clear about whether flaxseed affects prostate cancer risk or progression. Studies have given conflicting findings. Flaxseed provides Alpha-linolenic acid (ALA) - a form of omega-3 fat that some studies find may have anti-inflammatory ccompounds. Small amounts are also converted into another omega-3 fat, called EPA (eicosapentaenoic acid) which is a source of protective, anti-inlfammatory compounds. Because inflammation is associated with increased cancer risk, the anti-inflammatory effects of these omega-3 fats may help protect against cancer. Overall, however, studies on prostate cancer risk do not support any of the omega-3 fats in causing or preventing prostate cancer. Two short studies giving flaxseed to men with prostate cancer did show some reduced cancer cell growth compared to a control group, but more research is needed to confirm if there is a benefit for prevention or any stages or types of existing prostate cancer.
Medications and Flaxseed: Because of flaxseed lignans, there was some concern that flaxseed could interfere with cancer medications, such as tamoxifen, that block estrogen. Although human studies are limited, animal studies show that flaxseed does not interfere with the actions of common breast cancer medications.
Yet, flaxseed may decrease absorption of medications, so take it one hour before or two hours after any prescription or non-prescription medicine. Talk to your physician or healthcare provider about consuming flaxseed if taking anticoagulant supplements or medications.