Some studies have linked high intakes of dairy to increased risk of cancer. But others have found no connection, and even a reduced risk. The question is, which one's are unbiased studies and which one's are sponsored by the dairy industry? Scientists from the Kaiser Permanente research centre in California looked at the records of 1,500 women diagnosed with breast cancer between 1997 and 2000 and found that those with the disease who eat a single portion daily of a product containing full-fat milk could be 50 percent more likely to die.
US scientists suspect this is because milk and other dairy foods contain the hormone oestrogen, which encourages tumour growth.
There is already some evidence that diet plays a role in improving the chances of surviving cancer and preventing it returning. But this is the first study to show such a strong link between dairy products and breast cancer.
Pasteurized milk is perhaps one of the most nutritionally deficient beverages misappropriately labeled as a "perfect food." Raw milk enthusiasts have known for a very long time that unpasteurized milk is the ONLY milk worthy of consumption. Pasteurization destroys enzymes, diminishes vitamin content, denatures fragile milk proteins, destroys vitamins C, B12 and B6, kills beneficial bacteria, promotes pathogens and is associated with allergies, increased tooth decay, colic in infants, growth problems in children, osteoporosis, arthritis, heart disease and cancer.
Estrogen Hormones In Dairy To Blame
US scientists suspect this is because milk and other dairy foods contain the hormone estrogen, which encourages tumour growth.
Natural estrogens are up to 100,000 times more potent than their environmental counterparts, such as the estrogen-like compounds in pesticides.
Among the routes of human exposure to estrogens, we are mostly concerned about cow's milk, which contains considerable amounts of female sex hormones," said Ganmaa Davaasambuu, Ph.D. Dairy, she added, accounts for 60 percent to 80 percent of estrogens consumed.
Part of the problem seems to be milk from modern dairy farms, where cows are milked about 300 days a year. For much of that time, the cows are pregnant. The later in pregnancy a cow is, the more hormones appear in her milk.
Milk from a cow in the late stage of pregnancy contains up to 33 times as much of a signature estrogen compound (estrone sulfate) than milk from a non-pregnant cow.
In a study of modern milk in Japan, Ganmaa found that it contained 10 times more progesterone, another hormone, than raw milk from Mongolia.
One study compared diet and cancer rates in 42 counties. It showed that milk and cheese consumption are strongly correlated to the incidence of testicular cancer among men ages 20 to 39. Rates were highest in places like Switzerland and Denmark, where cheese is a national food, and lowest in Algeria and other countries where dairy is not so widely consumed.
Cancer rates linked to dairy can change quickly, said Ganmaa. In the past 50 years in Japan, she said, rising rates of dairy consumption are linked with rising death rates from prostate cancer - from near zero per 100,000 five decades ago to 7 per 100,000 today.
Butter, meat, eggs, milk, and cheese are implicated in higher rates of hormone-dependent cancers in general, she said. Breast cancer has been linked particularly to consumption of milk and cheese.
Around one in eight women will develop breast cancer at some point in their lives and there are around 50,000 new cases a year.
Although survival chances are far better than other forms of the illness it still leads to 11,800 deaths annually.
They had all completed questionnaires on how often they consumed dairy products, the sizes of portions and what specifically they ate.
They point out that most milk consumed in Britain, U.S. and Canada comes from pregnant cows and is rich in the hormone oestrogen.
This is known to trigger tumour growth and there are particularly high levels in full-fat dairy foods.
In fact women who ate one portion of full-fat dairy a day were 64 percent more likely to die from any cause - not just breast cancer.
Dr Bette Caan, who led the research said: 'High-fat dairy is generally not recommended as part of a healthy diet.
Many women who have just been diagnosed with breast cancer ask their doctor whether they should change their diet.
Susan Kutner, chair Kaiser Permanente Northern California Regional Breast Care Task Force, said: 'Women have been clamouring for this type of information.
'They're asking us, 'Tell me what I should eat?'
Sally Greenbrook, Senior Policy Officer at Breakthrough Breast Cancer, said: 'This study specifically looks at women who have already been diagnosed with breast cancer and how dairy products may affect them.
'Any women who have had breast cancer and are concerned about their diet should discuss this with their doctors.
'For a number of health reasons it's advisable that all women should follow a healthy balanced diet. It helps you to maintain a healthy weight which, together with good practices such as lower alcohol intake and regular physical activity, can help to reduce your breast cancer risk and improve overall well-being.
'There are many risk factors for breast cancer, not just diet.'