Does Breastfeeding Reduce Breast Cancer Risk? A Deep Dive Into the Research

By The SABI

Breastfeeding is often described as natural, instinctive, even effortless, yet in reality, for many women, it is anything but. It demands energy, patience, and resilience. It reshapes your daily rhythms, your body, and often your identity. Between our team and families, we’ve collectively breastfed for over four years, and we know firsthand the mix of intimacy and exhaustion, joy and doubt that comes with it.

Amid all the practical concerns about latching, supply, and sleep deprivation, there’s another question that often surfaces in conversations with mothers: does breastfeeding protect me in the long run? More specifically, many women want to know whether breastfeeding can reduce their risk of developing breast cancer, a disease that affects 1 in 8 women over their lifetime (American Cancer Society).

It’s a profound question, not just because of the statistics, but because breast cancer touches almost every family. And the answer, supported by decades of epidemiological research, is yes. Breastfeeding is not only nourishment for your baby; it also offers a measure of protection for mothers themselves. The association is dose-responsive, meaning that the longer a woman breastfeeds over her lifetime, the more her risk of breast cancer appears to decline.

This isn’t abstract. It matters in concrete, human ways: sustaining breastfeeding may mean more peace of mind, more years with your children, more resilience in your own health story. At the same time, the protective effect is modest for any one individual, which is why it should be seen as one piece of a broader prevention puzzle, alongside nutrition, movement, screening, and support.

In this deep dive, we’ll look at what the science actually says.

The Evidence: A Dose-Response Relationship

A landmark pooled analysis of data from nearly 50,000 women with breast cancer found that the relative risk decreases by about 4.3% for every 12 months of breastfeeding, on top of a 7% reduction for each birth (Lancet).

The World Cancer Research Fund and American Institute for Cancer Research have also classified breastfeeding as a convincing protective factor against breast cancer, recommending it as part of population-level cancer prevention strategies.

Duration and Exclusivity Matter

The protective effect is closely tied to duration. The more months a woman breastfeeds across her life, the stronger the association with reduced breast cancer risk. Studies also suggest that exclusive breastfeeding, meaning no formula or complementary foods may provide additional protection compared with partial breastfeeding.

This aligns with biology: exclusive breastfeeding maintains lactational amenorrhoea (no ovulation), lowering cumulative exposure to oestrogen, which is a driver of breast cancer risk.

Subtypes: Why It Matters for Triple-Negative Breast Cancer

The association isn’t uniform across all breast cancer subtypes. Research indicates that breastfeeding is linked to a reduced risk of both oestrogen receptor–positive cancers and triple-negative breast cancer.

This matters because TNBC is aggressive, harder to treat, and disproportionately affects younger women and Black women. Importantly, studies suggest that parity without breastfeeding may increase TNBC risk, while breastfeeding helps to offset this excess risk (Breast Cancer Research).

High-Risk Women: BRCA1 Carriers

For women with inherited risk, breastfeeding still appears to make a difference. A multicentre study showed that BRCA1 carriers who breastfed for at least 12 months had a 32% lower risk of breast cancer, compared with those who did not.

The effect was not as clear for BRCA2 carriers, highlighting the need for tailored prevention strategies. Still, for BRCA1 carriers, breastfeeding remains one of the few modifiable risk factors.

Biological Mechanisms

Several overlapping mechanisms may explain the protective effect of breastfeeding:

Reduced lifetime oestrogen exposure: Lactational amenorrhoea suppresses ovulation, lowering cumulative exposure to circulating oestrogens (NCI).
Breast tissue remodelling: During lactation and involution, differentiated mammary cells are shed, potentially eliminating cells with DNA damage.
Epigenetic and immune changes: Breastfeeding induces shifts in immune regulation and gene expression in breast tissue, which may reduce long-term susceptibility to malignancy.

These mechanisms are not mutually exclusive, together, they help explain why breastfeeding consistently shows a protective signal across diverse populations.

Real Life: Supporting Women to Breastfeed Longer

The evidence is clear, but the practical reality is often harder. Many women stop breastfeeding earlier than they want to, usually because of concerns about milk supply, stress, or lack of support. Globally, more than 60% of mothers stop earlier than planned (WHO).

Practical support matters: skin-to-skin contact, frequent feeding or pumping, and nourishing foods all help sustain supply. Gentle, lactation-friendly infusions can also play a supportive role. Our Breastfeeding Herbata blends fennel, nettle, moringa, oat straw, and calming herbs like tulsi and vervain, chosen not as cancer-prevention tools, but to help mothers feel nourished, calm, and supported during breastfeeding.

The scientific consensus is that breastfeeding reduces a mother’s risk of breast cancer, with the protective effect strengthening the longer she breastfeeds. The association is strongest for oestrogen receptor–positive and triple-negative breast cancers, and evidence suggests significant benefit for BRCA1 carriers as well.

Biologically, this protection likely comes from reduced hormonal exposure, the shedding of potentially precancerous breast cells, and favourable immune and epigenetic shifts.

Breastfeeding is not the only lever for cancer prevention, and it is not always possible for every woman. But where it is possible, and when women are given the right support, it offers benefits that extend far beyond infancy, protecting not just children but mothers themselves.

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

Collaborative Group on Hormonal Factors in Breast Cancer. Breast cancer and breastfeeding: collaborative reanalysis. Lancet. 2002.
World Cancer Research Fund / AICR: Breastfeeding and cancer risk.
American Cancer Society: How common is breast cancer?.
National Cancer Institute: Breastfeeding and breast cancer risk fact sheet.
Islami F, et al. Breastfeeding and breast cancer risk by receptor status. Breast Cancer Res Treat. 2015.
Warner ET, et al. Parity, breastfeeding, and risk of triple-negative breast cancer. Breast Cancer Res. 2016.
Kotsopoulos J, et al. Breastfeeding and breast cancer risk in BRCA1/2 mutation carriers. J Natl Cancer Inst. 2002.
Schedin P. Pregnancy-associated breast cancer and involution. Nat Rev Cancer. 2014.