Breast Cancer Prevention & How to Reduce Your Risk

19 January 2021

Understanding your personal risk of breast cancer and getting regular screening can help improve your chance of better outcomes. There are also ways to manage some breast cancer risk factors through healthy lifestyle decisions and risk-reducing strategies.


Researchers have found that weight gain in middle life increases breast cancer risk. [1].

There is no one single diet, food or supplement that can prevent or lower your risk of breast cancer. However, a healthy diet is still important to prevent against disease.


Exercise can also positively affect other risk factors such as obesity and insulin resistance. It has also been shown that post-diagnosis physical activity in women with breast cancer can improve the survival chance of the patients [2]. Ideally, exercise at least 30 minutes per day, 5 days per week at a moderate to high intensity.

Women can decrease their risk of breast cancer by engaging in regular exercise. Research has shown that in postmenopausal women, exercise and physical activity decreases the risk for breast cancer by changing oestrogen, insulin and insulin-like growth factor 1.

Weight Control

Obesity is associated with a 20% to 40% increased risk of breast cancer in post-menopausal women. In patients diagnosed with breast cancer, obesity is associated with a 33% increased risk of cancer recurrence and of death from any cause [3].

Additionally, gaining weight as an adult is associated with an increased risk of post-menopausal breast cancer. The risk increases by about 6% for each 5 kg increase in a woman’s weight.

However, having a higher BMI before menopause is associated with a decreased risk of premenopausal breast cancer. For each 5-unit increase in BMI, the risk of premenopausal breast cancer is decreased by about 7% [4]. Importantly, obesity throughout life increases the risk of many other diseases such as heart disease and other cancers, leading to a higher rate of premature death.

Family History Awareness

It’s important to be aware of your family history with breast cancer, as a person’s risk of being diagnosed with breast cancer increases if they have a close relative who has had breast cancer.

Approximately 5-10% of breast cancers are due to a strong family history of genetic mutation such as BRCA1 or BRCA2. Some women with strong family histories receive genetic testing to see if they have one of these mutations.


Globally, alcohol is identified as a risk factor for a range of soft tissue cancers, including breast cancer [5]. Alcohol is the most-established dietary risk factor, thought to be due to the increase of endogenous oestrogen levels it causes [6].

Women who drink one standard glass of alcohol (10g) a day have a 7 per cent higher risk of breast cancer than women who never drink alcohol [7].

Evidence suggests there is no safe level of alcohol consumption in regard to an increased breast cancer risk, with a meta-analysis of 222 articles finding even light drinking (up to one drink per day) increases the risk of female breast cancer.


Several studies have shown there is an association between tobacco smoking and the risk of breast cancer. This association is observed particularly in women who smoke for a long time, or who smoke for a long time prior to their first pregnancy [8].

Tobacco smoke contains more than 5000 chemical compounds, including more than 70 that are known to be carcinogenic [9]. Smoking has been found to be a major cause of heart disease, lung cancer and many other cancers, therefore not smoking is the best choice for your health.


Tamoxifen, a medication that is commonly used to treat breast cancer, also helps prevent breast cancer from occurring. It may be considered for women who are at a high risk of breast cancer due to their personal or family history [10].

Things you cannot change

Unfortunately, you have no control over these risk factors. It’s still important to be aware of them, so you can talk to your doctor about the screening you need.

  • Being a woman
  • Getting older
  • Having a family history of cancer
  • Breast density
  • Having previous breast issues

Breast Cancer Screening

The earlier breast cancer is found, the better the chance of survival. Screening mammography can detect breast cancer at its earliest state, before it can be felt.

In New Zealand, women aged between 45 and 69 years are able to receive a free mammogram every two years. Book your mammogram with BreastScreen Aotearoa! Freephone 0800 270 200