The government advises exclusive breastfeeding for first six months
Breastfeeding for a year over the course of a woman's life helps cut the risk of breast cancer, research says.
The World Cancer Research Fund analysed 7,000 previous studies and found it reduced the risk by 4.8%.
Women have a one in nine chance of getting breast cancer in their lifetime, meaning that the overall reduction in risk is just above 0.5%.
Researchers said it was important that women realised the positive effect of breastfeeding.
Breastfeeding has been linked to lower obesity levels in children and is known to confer immunity to the newborn against a clutch of infections, including respiratory diseases.
However, a recent survey found that only one in four women in the UK knew breastfeeding cut the chance of them developing breast cancer.
Over three quarters of mothers initiate breastfeeding, but of this, only 22% are still breastfeeding at six months.
Breastfeeding has been found to lower the levels of some cancer-related hormones in the mother's body, reducing the risk of the disease.
At the end of breastfeeding, the body has also been found to rid itself of any cells in the breast that may have DNA damage. This reduces the risk of breast cancer developing in the future.
Lead researcher Dr Rachel Thompson said: "We want to get across the message that breastfeeding is something positive that women can do to reduce their risk of breast cancer.
"Because the evidence that breastfeeding reduces breast cancer risk is convincing, we recommend women should breastfeed exclusively for six months and then continue with complementary feeding after that."
Dr Lesley Walker, Cancer Research UK’s director of information, said: "Aside from family history, age, a previous breast cancer and certain benign breast conditions, we know that the major things that affect a woman’s risk of breast cancer include how early and how many children she has, how early she starts her periods and how late the menopause begins, and whether or not she chooses to breastfeed."