By The SABI
Breastfeeding changes everything. Your routines, your sleep, your energy, and deep inside your body, it changes your hormones too. Between our team and families, we’ve collectively breastfed for over four years, and we’ve felt those shifts: the sudden surges of oxytocin that calm you, the deep tiredness that comes with constant prolactin release, the subtle steadiness that sets in as months go by.
But what many mothers don’t realise is that these hormonal changes may also protect against breast cancer in the long run. Large-scale analyses show that women lower their breast cancer risk by about 4.3% for every 12 months of breastfeeding (Lancet). The mechanism is not only physical (like the shedding of breast cells), it’s also deeply hormonal.
Here’s what science tells us about the hormonal pathways behind breastfeeding’s protective effect.
Prolactin: The Milk-Making Hormone
Prolactin is best known for its role in stimulating milk production, but it also orchestrates changes in breast tissue. During sustained breastfeeding, prolactin levels remain elevated, maintaining lactation and suppressing ovulation. This means fewer menstrual cycles, less exposure to oestrogen and progesterone, and lower cumulative hormonal stimulation of breast cells (NIH).
This “quieting” of the menstrual cycle is one of the clearest links between prolactin and reduced breast cancer risk: fewer cycles, less hormonal wear-and-tear.
Oxytocin: More Than the “Love Hormone”
Every let-down reflex - when milk releases - is triggered by oxytocin. Beyond bonding and calm, oxytocin also stimulates breast duct contraction, helping clear cells and milk. Animal and human studies suggest oxytocin may have direct anti-tumour effects, including promoting apoptosis (programmed cell death) in abnormal cells (PubMed).
Regular surges of oxytocin during breastfeeding may therefore not only nurture emotional connection but also help keep breast tissue healthy on a cellular level.
Oestrogen Suppression: Less Fuel for Tumour Growth
High lifetime exposure to oestrogen is one of the strongest risk factors for breast cancer. During breastfeeding, oestrogen levels drop significantly due to lactational amenorrhoea (no ovulation).
By reducing ovulatory cycles, breastfeeding reduces the cumulative oestrogen dose breast tissue receives. Epidemiological studies confirm that women who breastfeed longer have lower risk of oestrogen receptor–positive breast cancers, the most common subtype (World Cancer Research Fund).
Progesterone and Breast Cell Differentiation
Pregnancy and breastfeeding push breast cells to fully differentiate, moving them from a proliferative state (higher cancer risk) to a mature, milk-producing state (more resistant to malignant change). Progesterone, in balance with prolactin, drives this maturation.
Research shows that fully differentiated cells are less likely to undergo cancerous transformation, offering long-term protection (Nature Reviews Cancer).
Insulin and IGF-1 Pathways
Breastfeeding also alters insulin and insulin-like growth factor-1 (IGF-1) signalling. Lower circulating IGF-1 is associated with reduced cancer risk, since IGF-1 promotes cell growth and survival. Studies suggest breastfeeding helps downregulate IGF-1 activity, creating a less pro-cancer environment (Journal of Clinical Oncology).
Cortisol and Stress Hormones
Finally, breastfeeding’s hormonal environment is calming. The combined effects of prolactin and oxytocin lower stress reactivity and reduce cortisol spikes (Frontiers in Neuroendocrinology). Chronic high cortisol has been linked to tumour-promoting inflammation; breastfeeding may therefore indirectly lower cancer-promoting stress physiology.
Understanding the hormonal pathways is fascinating, but sustaining breastfeeding in the real world can still be difficult. Many mothers stop earlier than intended because of stress or milk supply worries (WHO).
Supportive nutrition helps here. Our Breastfeeding Herbata was designed with herbs like fennel, nettle, moringa, and tulsi to help mothers feel nourished and calm. While not a cancer-prevention product, it can play a role in supporting supply and easing the hormonal transitions that come with nursing.
Breastfeeding protects against breast cancer not only through physical processes but through hormonal pathways: higher prolactin and oxytocin, lower oestrogen and IGF-1, and more stable cortisol patterns. These shifts reduce hormonal stimulation of breast tissue, encourage healthy cell turnover, and create a more resilient environment in the breast.
The evidence is strongest for oestrogen receptor–positive cancers but also extends to triple-negative breast cancers, with additional benefits observed in high-risk women such as BRCA1 carriers.
Breastfeeding is not always possible, and it should never be a source of guilt. But when supported, it offers one of the rare opportunities where what nourishes your baby may also help protect you, hormonally and long into the future.
HORMONAL & PROUD
Created as a brand to help women navigate the toughest moments in pregnancy, childbirth, postpartum — and practically every stage of life –– The SABI is changing the narrative around our hormones from one of taboo, embarrassment, and loneliness to awareness and even, pride. As more than a wellness brand, The SABI offers a carefully-crafted line of products to carry you through your hormonal journey, including rituals, supportive tools, and ancient herbal remedies that have been tested time and time again by women and now come backed by medicine. The SABI is a blend of science and nature conceived by women who have experienced the joys and deep struggles of bringing a child into the world, the pains of a heavy, difficult period, miscarriage, and difficulty conceiving.
We invite you to get to know your body and its cycles better –– to really understand what is going on inside. Learn to use your hormones to your advantage no matter your stage of life, and know that you can support and balance your hormone levels. We are here to help with the information, understanding and natural tools to support your body and the emotional process along with it.
DISCLAIMER
The SABI blog and articles are not meant to instruct or advise on medical or health conditions, but to inform. The information and opinions presented here do not substitute professional medical advice or consultations with healthcare professionals for your unique situation.
References
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Collaborative Group on Hormonal Factors in Breast Cancer. Breast cancer and breastfeeding: collaborative reanalysis. Lancet. 2002.
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World Cancer Research Fund: Breastfeeding and cancer risk.
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Neville MC, et al. Endocrine control of lactation. NIH Bookshelf.
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Cassoni P, et al. Oxytocin and its receptors in cancer: a critical review. Endocr Relat Cancer. 2014.
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Schedin P. Pregnancy-associated breast cancer and involution. Nat Rev Cancer. 2014.
