Factors Which Increase and Decrease
Breast Cancer Risk
http://bcpinstitute.org/booklet4.htm#introduction
Factors Which INCREASE Breast Cancer Risk
| Factor | Mechanism |
| Alcohol | Increases estrogen exposure by impairing liver function |
| Benign proliferative breast disease | Result of increased estrogen exposure |
| BRCA genes | Inherited defects in cancer defense genes |
| Cigarette smoking | Benzopyrenes damage DNA |
Contraceptive steroids (in pills, patches, vaginal rings, IUDs or injectable forms) | Increases estrogen exposure |
| Early menarche | Increases estrogen exposure |
| Female sex | Increased estrogen exposure |
| High socio-economic group | Delayed childbearing |
| Higher education | Delayed childbearing |
Hormone replacement therapy (HRT) | Increases estrogen exposure |
| Increasing age | Premenopausal: Increases estrogen exposure Postmenopausal: Impairs immune function |
| Induced abortion | Leaves increased number of immature breast lobules and increases risk of premature births Increases estrogen exposure |
| Late childbirth (over 30 years old) | Increases exposure of Type 1 & 2 lobulesto estrogen before first birth; long susceptibility window |
| Late menopause | Increases estrogen exposure |
| Nulliparity (never bearing children) | Maturity of breast lobules does not occur |
| Premature birth before 32 weeks | Leaves increased number of immature breast lobules Increases estrogen exposure |
| Postmenopausal obesity | Increases estrogen exposure |
| Radiation | Damages DNA |
| 2nd trimester miscarriage | Leaves increased number of immature breast lobules |
Factors Which Decrease Breast Cancer Risk
| Factor | Mechanism |
| Breast feeding | Decreases estrogen by decreasing number of menstrual cycles and/or ovulation |
| Cruciferous vegetables (e.g., broccoli, Brussels sprouts or DIM supplements) | Indole-3-carbinol decreases estrogen exposure by causing estrogen to be changed to an inactive metabolite of estrogen |
| Early menopause | Decreases estrogen exposure |
| Exercise | Decreases estrogen exposure |
| Having children (especially starting at a young age) | Decreases number of immature breast lobules |
| Late menarche | Decreases estrogen exposure |
| Omega-3 fatty acids (e.g., olive, flax seed, walnut oils) | Unknown |
| Oophorectomy (removal of ovaries before menopause) | Decreases estrogen production |
| Soy isoflavonoids (phytoestrogens) | May block estrogen receptors |
Factors Which Have No Effect on Breast Cancer Risk
| Factor | Reason |
| Saturated fat | Saturated fat intake not related to obesity |
| Spontaneous abortions (miscarriages) in the first trimester | No increased levels of estrogen as found in healthy pregnancies |
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