Breast Cancer Causes and Prevention Strategies

8 Jan

Breast Cancer Causes and Prevention Strategies

The website of the New Zealand National Screening Unit includes the following information about risk factors for breast cancer:

“What causes breast cancer?

“Exactly why breast cancer develops in a particular woman is not clear. Breast cancer seems to be linked to hormones, especially the female hormone oestrogen. However, it is unlikely there is one single cause. A combination of factors, some known but others unknown, may trigger or promote the cancer.

“Risk factors and protective factors

“At present there are no certain ways of preventing breast cancer although there are some clues – known as risk factors and protective factors – about who is more likely or less likely to develop the disease. Many of these risk factors are linked to female hormones, especially oestrogen, for example, age at puberty, age at first pregnancy and age at menopause. Many risk and protective factors are uncertain or controversial.

“The risk factors for DCIS appear to be similar to those for invasive breast cancer.

“Most studies of risk factors have been done in women of European background, and risk factors may differ for women of different ethnicities.

“The risk factors listed below are common among women, but there is little they can do about most of them. Some relate to our lives many years before. A few risk factors provide the opportunity to reduce risk by making changes in our lives, but even making those changes cannot give a guarantee.

“Women who have the key risk factors should discuss this with their doctor who can advise them and, if necessary, develop a plan for regular checks that may include mammograms.

“Factors that increase the risk of breast cancer

Key risk factors

Growing older
Previous breast cancer
Previous breast biopsy showing a condition that increases risk
Strong family history
Inherited genetic factors
Exposure to repeated or high-dose radiation.

“Less important risk factors

Weight gain after 18
Current drinking of alcohol
Never had children
First child after 35
Hormone replacement therapy
Oral contraceptives
Depo-Provera contraceptive injection
Ovarian cancer
Being a twin.

No clear evidence*

High-fat, red meat diet
Environmental chemicals, such as pesticides
Heavy smoking and passive smoking
Use of statins – medicines to control cholesterol.
(*No clear evidence means that the results of studies have been mixed, or there is not enough evidence to say that it is proven.)

No evidence

Electric blankets
Hair colouring
Abortion or miscarriage
Tea or coffee
Underwire bras
Bruise or injury to the breast
Personality type
Cellphones, digital clocks, microwaves.

Factors that are protective

Protective factors

Menstruation starts at late age
Menopause occurs at a young age
First child at a young age
Having children, the more children the greater the protection

No clear evidence*

Low fat, high-fibre diet
Phyto-oestrogens – plant oestrogens
Green tea
Regular use of non-steroidal anti-inflammatory drugs.”

I think that the National Screening Unit is to be commended for giving women information about the “Key Risk Factors” and “Less Important Risk Factors”.  It is also good that the organisation has as acknowledged under the “No clear evidence” category those factors which may contribute to breast cancer risk, but which the organisation considers the evidence from studies is mixed, or not strong enough to consider that a risk is proven.

However I am concerned that under the category “No evidence” that the NSU has listed a number of risk factors that have been shown associated with increased breast cancer risk in a number of studies.

Electric blankets and breast cancer risk

The National Screening Unit states that there is “No evidence” that using electric blankets increases breast cancer risk.  This is untrue.  Electric blankets (and other sources of electromagnetic radiation) can increase breast cancer risk.  New Zealand scientist Dr Neil Cherry  (sadly deceased) reported in detail on the of electromagnetic fields and cancer in a paper titled “Electromagnetic Radiation Causes Cancer: The Implications for Breast Cancer” at the World Conference on Breast Cancer in Canada in 1999.  The PDF may be downloaded at this link:

The following two links are to studies that show an association between electric blanket use and increased breast cancer risk.  (There are also studies that do not show a link.)

If you have an electric blanket, it should only be used to heat the bed prior to getting into bed. It should then be switched off and unplugged at the wall.  Waterbeds with heating elements may also produce electromagnetic fields that increase breast cancer risk.  Their use is probably best avoided.

Hair dye and breast cancer risk

While the NSU has classified hair dye as being in the “No evidence” category as far as breast cancer risk is concerned there are in fact a number of studies that show increased risk of breast cancer and hair dye, both for women who are occupationally exposed to dyes as well as women who dye their hair.  Using hair dye is also associated with higher risk of some other types of cancer including non-Hodgkins lymphoma. (Confounding the picture is that fact that there are also studies that do not show an association between hair dye and breast cancer.)  What is undeniable is the fact that many hair dyes contain chemicals that are proven carcinogens.

If you dye your hair you can check whether it contains carcinogenic ingredients by checking the ingredient list against the list on this site.

You can check on whether your hair dye or other personal care or cosmetic products you may use contains hazardous ingredients by typing  the ingredients into the search engine at .  This database includes information about carcinogenicity as well as other hazards such as neurotoxicity.

A good introduction to carcinogens and cancer prevention can be obtained by visiting the website of the Cancer Prevention Coalition.  At the following link on their site you can download a free short (66 page) e-book produced for the the organisation’s Stop Cancer Before It Starts Campaign which deals with the politics of cancer prevention.  (The e-book is at the bottom of the page and can be obtained by clicking on the link “Stop Cancer”.)

For most women, hair dye is an entirely avoidable risk factor for breast and other cancers. (Henna which is a botanical product and hydrogen peroxide are safer alternatives to standard hair dyes.  It is important to check labels even on health food store products as some brands may  contain undesirable ingredients.  There can be reactions between different hair products.  If you are switching from chemical dyes to henna or hydrogen peroxide, consult someone knowledgeable so that you avoid inadvertently damaging your hair.)

Abortion and breast cancer risk

The NSU states that there is “No evidence” that abortion or miscarriage increases breast cancer risk.  This is incorrect.  There have been numerous studies that show increased risk of breast cancer in women with a history of induced abortion.  Miscarriage, especially before a first  full term pregnancy has been also associated with some increase in breast cancer risk.  There have also been studies that have not shown an increased risk of breast cancer for women who have had induced abortions or miscarriages.  The risk is controversial but appears to be real nonetheless. There certainly is not “No evidence”.

The following links include information on this issue: (link)

The following link is for a charity that has been set up to publicise the link between breast cancer and abortion.

More information can be found by googling abortion + breast cancer.

Obviously if you have had an induced abortion (for whatever reason) or have had a miscarriage, these are risks that cannot now be changed. However, the current denial about the link between abortion and breast cancer is not helpful.  It is important for women to know about this risk as part of making an informed decision if they are considering abortion for an unwanted pregnancy (as well as other risks associated with induced abortion such as the possibility of infection, haemorrhage and the potential for subsequent pregnancies to be put at risk through increased risk of miscarriage, premature birth etc.) For women who have already had an induced abortion or miscarriage, knowing that they may be at increased risk of breast cancer is important in making decisions about breast cancer screening.


Stress has been documented to increase the risk of ill health.  The NSU states that there is “no evidence” that stress contributes to breast cancer risk.  This is unfortunately untrue. A number of studies have shown a correlation between stress and increased risk of developing breast cancer, although it is  true that there are also studies that do not show a link.  Major life events, including those that take place in childhood such as death of parent or experiencing parental divorce appear to increase breast cancer risk.  Severe stress in adult life (such as death of a spouse) may also increase cancer risk.  Unfortunately stress is often unavoidable.  Stress can be managed, however, and acknowledging the potential for stress to cause bad health allows us to take stock of our situation, make changes to reduce stress and reduce the risk of  developing  stress-related disease.,f1000m,isrctn,f1000m,isrctn,f1000m,isrctn

Further sources of information about breast cancer causes and prevention strategies

This link provides a good overview of breast cancer risk factors and how these may be reduced.

This link is the beginning of a report on breast cancer that provides information about the politics of cancer, carcinogens, breast cancer prevention as well as some alternative treatments.

Disclaimer:  Information on this site is provided for informational purposes and is not meant to substitute for the advice provided by your own physician or other health professional.  Readers are urged to think carefully about the risks and benefits of different breast screening options and to seek additional information if necessary.  Inclusion of links to other websites on this site does not imply endorsement of that organisation by nor does it imply endorsement of by any other organisation or company.