Why the link with meat and milk?
When looking at the relationship between diet and breast cancer in 40 different countries, researchers found a link between meat, milk and cheese and breast (and ovarian) cancer. Meat was most closely associated, followed by cow’s milk and cheese. In contrast, cereals and pulses were shown to protect against breast cancer.
These researchers concluded that meat, and in particular, dairy foods could increase the development of hormone-dependent cancers such as breast cancer.
The reason scientists are concerned about dairy products is because the levels of hormones in milk have increased hugely over the last 100 years as modern dairy farming methods have intensified. The milk produced now is quite different to that produced many years ago; with modern dairy cows frequently impregnated while still producing milk. In fact, two-thirds of milk in the UK is taken from pregnant cows with the remainder coming from cows that have recently given birth. This means that the hormones, such as oestrogen, are very high in milk.
Is your milk bioactive?
Milk contains many biologically active molecules, including enzymes, hormones and growth factors. A typical glass of cow’s milk contains 35 hormones and 11 growth factors! In fact cow’s milk and dairy products are loaded with gonadal, adrenal, pituitary, hypothalamic and other hormones.
The detrimental health effects of consuming cow’s milk and dairy products are more widely discussed in Health! Viva's referenced report White Lies. It describes how saturated animal fat, animal protein, cholesterol, hormones and growth factors in dairy products are linked to a wide range of illnesses and diseases including some of the UK’s biggest killers such as heart disease, diabetes, prostate cancer as well as osteoporosis, eczema, asthma, Crohn’s disease, colic, constipation and even teenage acne. White Lies is available free online at www.vivahealth.org.uk or for £5.00 from Viva! Health.
For more information on British dairy farming methods see Viva!’s fully-referenced report The Dark Side of Dairy, at www.viva.org.uk or telephone 0117 944 1000 (Mon-Fri 9am-6pm).
As well as the animal fat, chemical contaminants and/or hormones found in meat, fish and dairy foods, certain growth factors in milk may also increase the risk of breast cancer. One growth factor under scrutiny is insulin-like growth factor 1 (IGF-1).
It is produced in the liver and body tissues of mammals and promotes cell growth and division, which is crucial for normal growth and development. But to do this it must be at the right levels. High IGF-1 levels can cause cells to grow uncontrollably. IGF-1 in cows and people is identical; therefore IGF-1 in cow’s milk could dangerously raise our levels of IGF-1, triggering our cells to become cancerous.
Over the last decade, IGF-1 has been linked to an increased risk of many cancers, including childhood cancers, lung, pancreatic, prostate, gastrointestinal, melanoma and breast cancer. When IGF-1 is added to human breast cancer cells in the laboratory it causes them to grow. IGF-1 may also transform normal breast tissue into cancerous cells. It has been suggested that high IGF-1 levels in the blood could be used by doctors to predict certain cancers in the same way that high cholesterol levels are currently used as a predictor of heart disease.
So what causes high IGF-1 levels in the blood? Because two-thirds of milk in the UK is taken from pregnant cows it not only has a hormone content that is markedly elevated, the amount of IGF-1 is also higher. IGF-1 is quite stable to both heat and acidic conditions and can survive the harsh conditions of both pasteurisation and stomach acid. So it is not destroyed during pasteurisation and may cross the intestinal wall and enter the blood. Regular milk ingestion after weaning may produce enough IGF-1 in breast tissue to encourage cell division and increase the risk of cancer.
Research from Harvard Medical School investigated the relationship between IGF-1 and breast cancer by looking at blood samples from a large group of women, 397 of whom were later diagnosed with breast cancer. They compared levels in these women with levels in women who did not develop the disease. Results showed that premenopausal (but not postmenopausal) women with high levels of IGF-1 were more likely to develop breast cancer than those with normal or low levels. This could be because IGF-1 levels fall as we get older, so postmenopausal women have lower levels to start with. Alternatively it could be that premenopausal women are more at risk because oestrogen enhances IGF-1 action and oestrogen levels are much higher before the menopause.
Diet and IGF-1
Numerous studies show that IGF-1 levels are higher in people who consume cow’s milk:
- Researchers from Harvard Medical School examined IGF-1 levels in over 1,000 healthy women and found that as animal protein (mainly from cow’s milk) intake increased, so did IGF-1
- Researchers from the Fred Hutchinson Cancer Research Centre in Washington also found that milk consumption was linked to IGF-1 levels
- A study from Creighton University in Omaha, NE, observed a 10 per cent rise in IGF-1 levels in people who increased their intake of non-fat milk from less than one-and-a-half servings to three servings per day
- Danish researchers measured the effect of cow’s milk on IGF-1 levels in 54 two-and-a-half year old boys. An increase from 200 to 600ml of cow’s milk a day caused a massive 30 per cent increase in IGF-1
- Researchers at Bristol University investigating diet and IGF-1 in 344 men found higher intakes of milk, dairy products and calcium were associated with higher levels of IGF-1. Lower levels of IGF-1 were associated with high vegetable consumption, particularly that of tomatoes
- A study from the Cancer Epidemiology Unit at the Radcliffe Infirmary in Oxford found vegans (who consume no animal products, including dairy) had a nine per cent lower IGF-1 level than meat-eaters and vegetarians
The research shows conclusively that diet has an important role in determining IGF-1 levels.
In her best-selling book Your Life in Your Hands, Professor Jane Plant CBE, Anglo American Professor of Applied Geochemistry at Imperial College, London, describes her very personal and moving story of how she overcame breast cancer by eliminating cow’s milk and all dairy products from her diet. Jane was diagnosed with breast cancer in 1987, had five recurrences of the disease and by 1993 it had spread to her lymphatic system. She could feel the tumour growing on her neck and was told that she had just three months to live, six if she was lucky.
Ever the scientist, Jane was determined to find a solution to this ‘problem’. She began looking at breast cancer rates around the world and saw that in rural China they are a great deal lower. However, among wealthy Chinese women with a more Western lifestyle (for example in Malaysia and Singapore), the rate of breast cancer is similar to that in the West. Furthermore, evidence shows that when Chinese women move to the West, their rates increase to match those of their host country. This suggests that diet and lifestyle (rather than genetics) must be a major cause, keeping the risk low in rural China and high in the UK.
Jane focused on the role of diet in breast cancer and to her surprise found that people in China consume more calories a day than people in the US but only 14 per cent come from fat compared to a massive 36 per cent in the West. This, coupled to the fact that Chinese people tend to be more physically active than people in the West, is why obesity affects far more people in the West than in China.
However, Jane recalls her diet had not been particularly high in fat and describes it as low-fat and high-fibre. Then she had a revelation: the Chinese don’t eat dairy produce. She had been eating low-fat yoghurt and skimmed organic milk up until this time and immediately stopped it. Within days the lump on her neck began to shrink and the tumour decreased and eventually disappeared, leading her to the conviction that the consumption of dairy products is a major cause of breast cancer. Although she received chemotherapy during this time, it did not appear to be working and so convinced was her cancer specialist that it was the change in diet that saved her life; he now recommends a dairy-free diet to all his breast cancer patients.
Jane eventually defeated cancer by eliminating all dairy products from her diet, replacing them with healthy alternatives and making some lifestyle changes. She now advises that if you do only one thing to cut your risk of breast cancer, make the change from dairy to soya.
Many women have used Jane’s advice about dairy to overcome breast cancer. What is most shocking is that until they read her book, most of them had no idea how diet could affect the course of this disease. Most doctors do not give any dietary advice to their cancer patients. One woman says “Thank you dear Jane for making this precious information available to us”. Another says “I am convinced that the book has saved my life”. Read these and other success stories at Cancer Support International’s website www.cancersupportinternational.com
No smoke without fire
How you cook certain foods can influence their role in breast cancer. A recent study published in the journal Epidemiology linked barbequed and smoked meats to breast cancer. It showed that postmenopausal women who eat a lot of grilled, barbequed and smoked meats have a whopping 47 per cent increased risk of breast cancer. It also showed that big meat-eaters who skimp on fruit and vegetables have a massive 74 per cent increase in risk. Why this effect was not seen in premenopausal women is unclear. That said, it would seem prudent for women of all ages to avoid barbequed and smoked meats, and to increase fruit and vegetable intake.