Found whilst looking for something else - in this instance iodine in Japanese breast milk - as is often the case.
As often the case with issues where there is no significant financial incentive because you cannot patent something, on this occasion iodine, and it is cheap, more research is required.
The paper is not too 'technical'. I abstract bits below to give a flavor of the review.
Free Full paper
http://jeffreydachmd.com/wp-content/...ntrol-2000.pdf
"In this paper we have focused on deficient iodine and
selenium intake as risk factors for breast cancer;
however, these elements have also been implicated in
the development of other hormone-dependent diseases,
such as ovarian [5, 97], uterine [5, 97, 98] and prostatic
carcinoma [99, 100]. In view of the complementary
nature of these two nutrients, a re-evaluation of optimal
iodine and selenium intake may be required. In-depth
studies, examining a combined role for these elements in
the prevention and treatment of cancer and other
degenerative diseases, would be a step in the right
direction"
"In estradiol-treated rats, iodine deficency has been
shown to lead to pathological changes similar to those
seen in benign breast disease ± cystic changes, per-
iductal fibrosis and lobular hyperplasia [19, 20].
Conversely, dietary iodine reintroduction has been
shown to reverse these pathological changes [20].
Thus, iodine deficiency appears to enhance mammary-
tissue sensitivity to estrogen."
"As with prevention, a role for iodine in the treatment
of breast cancer awaits further study.
Traditional
eastern Asian medicine has long used iodine-rich sea-
weeds as a cancer treatment to ``soften'' tumors and
``reduce'' nodulation [30, 31]. Recent work with animal
systems seems to support an antitumor e€ect for iodine"