There are studies out now that flax seed can promote cancer growth even though it is thought to inhibit it. It might be safer to stick to mainly chia seeds, and cut down on flax.
What is the evidence?
Most of the evidence for an anti-cancer effect of flaxseed and flaxseed oil comes from research using laboratory animals or cells grown in laboratory dishes. In one cell culture study, flaxseed lignans reduced stickiness and movement of breast cancer cells, both properties related to the cancer’s ability to spread or metastasize. Researchers have also found that mice fed flaxseed had reduced formation, growth, or spread of prostate cancer, breast cancer, and melanoma. Flaxseed reduced pre-cancerous colon polyps in one study of rats, but in another study showed no effect on intestinal cancer in mice. In a 2007 report, flaxseed reduced growth of breast cancer cells in mice and enhanced the effectiveness of tamoxifen, a standard drug for hormonal therapy. Since then, other studies have looked at tamoxifen and flaxseed in animals, but human studies are still needed to find out if the effects hold true for humans.
There have been some small studies of the effects of flaxseed in humans. A small study of 15 men found that a low-fat diet supplemented with flaxseed lowered their blood prostate-specific antigen (PSA) levels and slowed the growth of benign prostate cells. Another study of 25 men with prostate cancer found that a low-fat diet along with ground flaxseed reduced serum testosterone, slowed the growth rate of cancer cells, and increased the death rate of cancer cells. A 2008 study looked at men with prostate cancer who were scheduled for surgery. Researchers gave some men flaxseed while others ate their usual diets; some were put on low fat diets. The men who got the flaxseed had slower cancer growth than those who did not, regardless of total fat intake. This was a fairly small study that did not look at survival or relapse rates. A 2011 study that compared flaxseed and low fat diets in men with prostate cancer found that a low fat diet, but not flaxseed, helped lower certain factors in the blood that are linked to prostate cancer growth.
This information has been brought to you by the American Cancer Society