Q: I’ve heard that flaxseed can help lower blood cholesterol, but will it increase my risk of breast cancer?
A: 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 (the "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 AICR's Foods that Fight Cancer.
Written by Karen Collins, MS, RDN, AICR's Nutrtion Advisor.