I asked my oncologist about taking collagen and other supplements whilst taking Tamoxifen. High doses of Vitamin C got a definite NO GO. Ordinary doses of standard Vitamin C tablets are OK. Do not take anything containing estrogen. Doc wasn't sure about soy foods or Evening Primrose Oil. Basically, avoid anything containing estrogen. Collagen got a raised eyebrow and an OK but watch out if you have fish allergies. I'm going to see a dietitian. Phytoestrogens are in heaps of healthy foods. Presumably they are OK. I will try collagen for skin, hair and nails if need be. Sally Obermeder supplements are too expensive, though. I'm thinking omega 3 oil capsules would be beneficial, and help sore joints. I bet all of this has already been tried and tested by others on this forum.