Breast cancer

Our analysis of worldwide research on breast cancer

As part of the Continuous Update Project (CUP) – our ongoing programme to analyse global research on how diet, nutrition, physical activity and weight affect cancer risk and survival – we have analysed worldwide research to produce our report on breast cancer.

Published in May 2017, the report is the most rigorous, systematic, global analysis of the scientific research currently available on diet, weight, physical activity and breast cancer, and which of these factors increase or decrease the risk of developing the disease.

For the report, the global scientific research on diet, nutrition, physical activity and breast cancer was gathered and analysed by a research team at Imperial College London, and then independently assessed by a panel of leading international scientists.

The report reviewed evidence from 119 studies from around the world. The studies examined more than 12 million women and over 260,000 cases of breast cancer.

The report updates the breast cancer section of our 2007 Second Expert Report and the 2010 CUP Breast Cancer Report.

Many epidemiologic studies have classified breast cancer cases by menopausal status at time of diagnosis, and therefore in this report we chose to highlight associations between diet, weight, and physical activity separately in premenopausal and postmenopausal breast cancer, where possible.

Key findings: premenopausal breast cancer

There is strong evidence that:

  • consuming alcoholic drinks increases risk
  • undertaking vigorous physical activity decreases risk
  • being overweight or obese between the ages of about 18 and 30 years decreases risk
  • being overweight or obese in adulthood before the menopause decreases risk
  • developmental factors leading to greater linear growth (marked by adult attained height) increase risk
  • factors that lead to greater birthweight, or its consequences, increase risk
  • breastfeeding decreases risk (breast cancer type unspecified) in the mother

Key findings: postmenopausal breast cancer

There is strong evidence that:

  • consuming alcoholic drinks increases risk
  • being physically active (including vigorous physical activity) decreases risk
  • being overweight or obese between the ages of about 18 and 30 years decreases risk
  • being overweight or obese throughout adulthood increases risk
  • greater weight gain in adulthood increases risk
  • developmental factors leading to greater linear growth (marked by adult attained height) increase risk
  • breastfeeding decreases risk (breast cancer type unspecified) in the mother

Much of the new evidence reviewed in this report related to body fatness (including body fatness in young adulthood), adult weight gain, alcohol and vigorous physical activity. The increase in the amount and quality of the evidence enabled some exposures to be reviewed by hormone receptor status.

Recommendations

To reduce the risk of developing breast cancer, follow our Cancer Prevention Recommendations. Our ten Cancer Prevention Recommendations are for preventing cancer in general and include maintaining a healthy weight, being physically active, eating a healthy diet and limiting alcohol consumption (if consumed at all).

Read our blog on how just one alcoholic drink a day increases breast cancer risk.

A more detailed overview of the findings is provided in the Executive Summary of the report.