Australasian Science: Australia's authority on science since 1938

Is Milk Causing Breast Cancer?


Geoscientist Jane Plant attributes her remission from cancer to cutting diary from her diet. Is there any scientific basis to this?

By Matthew Flavel

Is there any basis to claims that a dairy-free diet can prevent breast cancer?

Milk and breasts are unlikely enemies. However, geoscientist Jane Plant has a different view. Plant contracted breast cancer in 1987 and for 6 years she experienced the remission and relapse cycle of the cancer an agonising five times before making a drastic change: she cut dairy products from her diet entirely.

This serious decision was based on a link she drew between the low-incidence of breast cancer in China and their populations’ incidental low consumption of dairy. Within 6 weeks of this new diet – and her continued chemotherapy treatment – the lump was gone.

The cancer remained absent for 18 years, but it reappeared at a stressful time for Plant during which her old dietary habits re-emerged. A switch back to her trusted dairy-free diet, plus the commencement of treatment with a prescribed oestrogen suppressor, saw the cancer disappear again.

Jane Plant has considerable credibility as a scientist. She is currently a Professor of Geochemistry at Imperial College, London. She has published widely, including the somewhat relevant discovery that nutrient deficiencies in livestock can be caused by the geochemistry of the land on which they live. In the past she also held the position of Chief Scientist of the British Geological Survey.

Plant has recruited cancer researcher Mustafa Djamgoz to co-write their recently released book Beat Cancer, which outlines their opinion on how cancer develops, how to live with it and how to stop it. Following worldwide news reports of her claims and celebrity backers as high-powered as Oprah Winfrey, the book has arisen to number 1 in Amazon’s oncology section.

Plant summarised her hypothesis in an interview with The Telegraph in June: “Cows’ milk is good for calves – but not for us”. But does the evidence support the theory?

Fortunately the role of dairy products in breast cancer has been extremely well researched. Unsurprisingly, it is not as simple as Plant proposes.

The first place to look for evidence on this topic is the Nurse’s Health Study run in association with Harvard University. This study followed 122,000 female nurses’ lives between 1980 and 1996 in the form of a biennial survey across a broad range of women’s health issues. Due to its scale and breadth, it is one of the most significant pieces of research into women’s health in history.

One of the topics covered by this research was the potential link between dairy products and breast cancer. While the study reported no association in post-menopausal women, in pre-menopausal women with a high intake of low-fat dairy there was a decreased risk of breast cancer.

Milk is a good source of calcium and vitamin D, both of which have a protective role against breast cancer. The Nurse’s Health Study showed that these components of milk reduced the risk of breast cancer regardless of fat intake, body mass index and alcohol consumption. These are all risk factors for breast cancer that milk offers protection from.

In 2010 the World Cancer Research Fund assessed the full spectrum of research published on the topic. The panel judged that evidence supporting an increased risk of cancer from dairy products was limited at best, while a decreased risk is probable.

However, Plant calls other components of milk into question as potentially causes of cancer. One of the main components she targets is growth factors present in milk. One such growth factor is insulin-like growth factor 1 (IGF-1). There is a growing body of evidence that this hormone may have a role in cancer development. Cows treated with growth hormones such as bovine somatotrophin produce a higher level of IGF-1 in their milk.

While this fact may be relevant in many parts of the world, the use of these growth hormones on dairy cows in Australia is prohibited. Therefore our milk has much lower levels of IGF-1 than countries that still treat their cows with growth hormones.

Regardless of this, a healthy adult gets almost no IGF-1 from their diet as it cannot easily be absorbed from the intestine. Rather, it is made inside the body to facilitate growth.

Plant also highlights the role of vascular endothelial growth factor (VEGF), which is found at elevated levels in both dairy cows with mastitis and breast cancer patients. This protein is actually produced by the body to do important tasks such as heal wounds and create blood cells. It can also be produced by cancers to continue growing. Therefore its elevated presence in both breast cancer patients and mastitis cows will not be from a dietary source. To quote Plant’s book: “As yet, there are no studies of a relationship between diet and circulating levels of VEGF”. This protein’s production is a consequence, not cause, of disease.

Plant has also argued that meat and dairy produce a more acidic environment inside the body that is ideal for cancer growth. Here she is advocating what is known as the alkaline diet, which has been widely criticised for lacking a strong research backing for its claims of increasing health by increasing the body’s pH. This concept does not take into account the body’s incredible ability to maintain its own steady pH. In addition, the body contains a range of different environments from acidic to alkaline. Digestion would be a very different experience if stomach acid became stomach alkaline.

It is true that cancer cells grow better in an acidic environment, but there is no evidence that this is caused by diet. Rather, there is significant evidence that cancer cells produce an acidic environment rather than simply move into one.

The fact that Plant has found a way to manage and continue to beat her cancer is one to be celebrated. It seems, however, that the dairy-free diet she advocates is not a solution that can be widely applied. As a single case study, her story is also conflicted by her research that has brought her into contact with a range of harmful chemical substances at concentrations that the average person is unlikely to ever meet.

Nevertheless, Plant’s new book offers positive practical steps to beat cancer, including tips on exercise, stress and the range of possible treatments. It is, however, wise to be wary of her claims that dairy should be the newest member at the top of the poisonous foods list. Likewise, excessive dairy consumption is not the answer either. Instead, a balanced and varied diet is essential.

The Cancer Council of Australia’s official position statement reiterates: “There appears to be no significant association between the consumption of dairy products and the risk of breast or ovarian cancer.” The same document promotes the positive role dairy plays as a good source of calcium, protein, vitamins and minerals.

Matthew Flavel is a PhD candidate in Human Nutrition at La Trobe University.