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What is it? Overview Usage Side Effects and Warnings

Lignans Side Effects and Warnings

Written by FoundHealth.

Safety Issues

Women who are pregnant or breastfeeding should avoid high intake of flaxseed or purified lignans. One study found that pregnant rats who ate large amounts of flaxseed (5% or 10% of their diet), or a purified lignan present in flaxseed, gave birth to offspring with altered reproductive organs and functions, and that lignans were also transferred to the baby rats during nursing. 1 In humans, eating 25 g of flaxseed per day amounts to about 5% of the diet. 2 High intake of lignans may not be safe for women with a history of estrogen-sensitive cancer, such as breast cancer or uterine cancer. A few test tube studies suggest that certain cancer cells can be stimulated by lignans such as those present in flaxseed. 3 Other studies found that lignans inhibit cancer cell growth. 4 As with estrogen, lignans' positive or negative effects on cancer cells may depend on dose, type of cancer cell, and levels of hormones in the body. If you have a history of cancer, particularly breast cancer, talk with your doctor before consuming large amounts of flaxseeds.

Other potential concerns are discussed in the safety section of the Flaxseed article.


  1. Tou JC, Chen J, Thompson LU. Flaxseed and its lignan precursor, secoisolariciresinol diglycoside, affect pregnancy outcome and reproductive development in rats. J Nutr. 128(11):1861-8.
  2. Thompson LU. Experimental studies on lignans and cancer. Baillieres Clin Endocrinol Metab. 12(4):691-705.
  3. Adlercreutz H, Mazur W. Phyto-oestrogens and Western diseases. Ann Med. 29(2):95-120.
  4. Adlercreutz H, Mazur W. Phyto-oestrogens and Western diseases. Ann Med. 29(2):95-120.


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