Hi @mehrnaz and welcome to Connect.
Here's some information from Memorial Sloan Kettering Cancer Center about chia seeds, however not specifically related to estrogen positive cancer. https://www.mskcc.org/cancer-care/integrative-medicine/herbs/chia

You might also be interested in this video with Dr. Dawn Mussallem, a Mayo Clinic physician and lead in the integrative medicine and health program within the Breast Center. Dr. Mussallem is a cancer survivor herself and shares information about food and diet that helped her and has helped her patients.
– Cancer-Fighting Foods https://connect.mayoclinic.org/webinar/cancer-fighting-foods/

Have you considered talking to an oncology nutritionist or dietitian about your questions about chia seeds?

The link does not lead to the video. Is there a different link?

The video should show on this page https://connect.mayoclinic.org/webinar/cancer-fighting-foods/ You have to click the play button in the middle of the image. Does that work for you, @marykaym63 ?