How pregnancy and breastfeeding protect against cancer: Australian researchers in breakthrough

The findings were published in the prestigious journal Nature magazine. Loi described this as “a paradigm shift in the way we understand the immune system and its role in long-term protection from breast cancer.”

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Previous research estimated that a woman’s risk of breast cancer decreases by 7 percent each time she gives birth, and by an additional 4.3 percent for every 12 months of breastfeeding.

Loi emphasized that her research focuses on understanding a biological mechanism and is not intended to make judgments about personal decisions about having children or breastfeeding.

“Even if women breastfeed, it’s not a 100 percent guarantee that you won’t get breast cancer,” she said.

Any period of breastfeeding offers protective benefits, but six months or longer has proven to be the most advantageous, Loi said.

Approximately 58 Australians are diagnosed with breast cancer every day. It is the most common cancer among women, and one in seven people is diagnosed with this disease.

National Breast Cancer Foundation executive director Dr. Cleola Anderiesz said the research represents a major leap forward in our understanding of how reproductive history may affect long-term breast cancer risk.

“If these findings can be translated into preventive strategies or new treatments, they have the potential to significantly reduce the incidence of breast cancer and ultimately save lives,” he said.

The study examined healthy breast tissue from more than 260 women who had undergone a breast reduction or preventive mastectomy and found that those who had had children had significantly more T cells.

The researchers then introduced cancerous cells into the mammary fat pads of the mice and observed that the growth rate was much slower in the mice that had given birth and were breastfeeding. When tumors developed in this group of mice, they were much smaller and contained T cells.

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When the researchers removed these T cells, this protection evaporated and the tumors grew as quickly as in the null mice.

Finally, the team investigated the outcomes of women diagnosed with triple-negative breast cancer, the most aggressive form of the disease.

“We found that women who had breast-fed did better from triple-negative breast cancer than those who had not breast-fed…they had more immune cells in their tumors,” Loi said.

Stephanie, who did not want her last name to be published for privacy reasons, is breastfeeding her 20-month-old daughter Eliza.

She said breastfeeding is a learned skill that allows her to comfort and bond with her two daughters while providing them with many health benefits. He said he was excited about the research findings.

“The health benefits for women are a bonus,” he said.

Stephanie, who lives in Glen Huntly in Melbourne’s south-east, said many women plan to breastfeed but find it difficult once their babies are born and struggle to access the right support.

Before her eldest daughter, April, was born in 2021, she attended a breastfeeding education course with the Australian Breastfeeding Association and found it invaluable.

“There was a woman in the front of the group who was breastfeeding her newborn baby, and we were able to ask her questions,” she said. “Being the first person in my circle of friends to have a baby, I don’t think I’ve ever seen anyone breastfeeding. It was really powerful.”

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Victoria Marshall-Cerins, executive officer of the Australian Breastfeeding Association, hopes the findings will raise awareness of “how extraordinary breastfeeding is in protecting women’s health”.

While 96 per cent of Australian mothers started breastfeeding, only 16 per cent said they were exclusively breastfeeding their babies at six months.

The World Health Organization recommends that a baby be exclusively breastfed for the first six months of life, then continue breastfeeding with appropriate foods for two years or longer.

“Women are not supported to achieve their breastfeeding goals,” Marshall-Cerins said.

“We are denying women access to this incredibly preventive pro-health activity and not supporting babies’ access to optimal nutrition.”

Marshall-Cerins said she believes inconsistent breastfeeding advice and unsupportive community attitudes are driving down breastfeeding rates. She said women return to work more quickly after having a baby and need supportive employers who allow them to combine breastfeeding and working.

He said that a very small portion of women and babies cannot breastfeed due to physiological and neurological disabilities.

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