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Prostate cancer and flaxseed

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Katrina Claghorn, MS, RD
Last Modified: February 17, 2002

Dear OncoLink "Ask The Experts,"

Is there harm to adding flaxseed, linseed oil or any other phytoestrogen to the diet for the man with prostate cancer in watchful waiting?  

Katrina Claghorn, MS, RD, registered dietitian at the Abramson Cancer Center of the University of Pennsylvania, responds:

Adding flaxseed to your diet may be beneficial. A study found that when flaxseed was added to a low fat diet (20% of total calories from fat) there was a decrease in mean total testosterone and free androgen index, as well as serum cholesterol. Flaxseed oil however is not recommended since it may promote tumor growth. Also lignans, which are the compounds with the estrogen-like activity, are not in the oil.

Flaxseed and soy are the foods most commonly associated with phytoestrogens. However, they are present in other foods including legumes (lentils, kidney beans, black beans, chick peas), grains, vegetables, seeds and fruits. So shifting to a plant-based diet, which emphasizes these foods, would be healthy decision for a person who has prostate cancer.