Soluble fiber was associated with lower risks of breast cancer, and higher total fiber intake was associated with a lower risk in both premenopausal and postmenopausal women.
Soluble fibre include pectins and beta glucans (found for example in foods like fruit and oats) and insoluble fibre including cellulose (found for example in wholegrains and nuts).
What is important to remember is that fibre-rich foods typically contain both types of fibre.
"Our study contributes to the evidence that lifestyle factors, such as modifiable dietary practices, may affect breast cancer risk," said Maryam Farvid from the Harvard University's T.H. Chan School of Public Health.
Consuming a diet high in fiber was linked with a reduced incidence of breast cancer in an analysis of all relevant prospective studies, said the study published online in peer-reviewed journal CANCER.
Since previous studies have generated inconsistent results regarding the potential relationship between fiber intake and breast cancer, Farvid and her colleagues searched for all relevant prospective studies published through July 2019.
When the investigators pooled data from the 20 observational studies they identified, individuals with the highest consumption of fiber had an eight percent lower risk of breast cancer.
"Our findings provide research evidence supporting the American Cancer Society dietary guidelines, emphasising the importance of a diet rich in fiber, including fruits, vegetables, and whole grains," said Farvid.
Fibre-rich foods include wholegrain bread and oats, barley and rye; fruit such as bananas, apple. berries, pears, melon and oranges; vegetables such as broccoli, carrots and sweetcorn, Peas, beans and pulses, nuts and seeds and potatoes with skin.