Drinking milk increases men's risk of prostate cancer, according to new research. A large scale study found those who downed around three-quarters of a pint a day were 25 per cent more likely to develop the disease.
This was compared to peers consuming less than a quarter of a pint a week. The white stuff contains stimulants that fuel cell division. Scientists advised milk lovers to switch to vegan varieties such as soy, oat and cashew.
Interestingly, there was no such link with yoghurt and cheese. Potentially harmful hormones and proteins are lost during fermentation. Lead author Professor Gary Fraser, of Loma Linda University, California, said the phenomenon applied to reduced and non fat milks, as well as full fat.
He said: "Our findings add important weight to other evidence associating dairy products, rather than non-dairy calcium, as a modifiable risk factor for prostate cancer."
They were based on more than 28,000 men in the US tracked for an average of nearly eight years, all of whom were initially cancer free. Food frequency questionnaires showed they had had a wide range of dairy and calcium exposure.
By the end of the study period, state cancer registries reported 1,254 new prostate cancer cases among the participants during follow-up. Non-dairy calcium from nuts, seeds, green vegetables, legumes, fruits and fortified cereals was separated from dairy foods intake.
Prof Fraser said: "Because our study cohort showed a great disparity and divergence of dairy intake and calcium levels, we could ask the question with unusual strength." Interestingly, results did not show a uniform rise in risk in men with incrementally more dairy intake.
In other words, increasing dairy intake by 50-gram increments did not yield the same risk increases as the portions grew larger and larger. Prof Fraser said: "Most of the continuing increase in risk is done with by the time you get to 150 grams, about two-thirds of a cup of milk per day.
"It is almost as if some biological or biochemical pathway is saturated at about two-thirds of a cup of milk per day."
Prior studies may have missed the non-uniform rise in risk between dairy consumption and prostate cancer if most of those participants already drank more than one cup of milk per day. This study allowed researchers to compare an extensive range of dairy consumption, including very low levels.
Data provided little evidence of an association between calcium intake and prostate cancer. Prof Fraser said: "One interpretation is that dairy foods, or some closely associated unknown risk factor, are causally related to the risk of prostate cancer."
The sex hormone content of dairy milk could be the key. Up to 75 percent of lactating dairy cows are pregnant, and prostate cancer is responsive to hormones. Further, prior reports have associated intake of dairy and other animal proteins with higher blood levels of a hormone, insulin-like growth factor-1 (IGF-1), which is thought to promote certain cancers, including prostate.
The same team recently identified a link between drinking milk and breast cancer in women. Prof Fraser said: "The parallels between our breast cancer in women paper a year ago and this paper relating to men, are striking. It seems possible that the same biological mechanisms are at work."
As further studies investigate how dairy consumption could increase prostate cancer risk, he advises prudent men with a family history of prostate cancer or other risk factors would “be cautious” about consuming even moderate levels of dairy milk as part of their diet until this is clarified.
Prof Fraser added: "If you think you’re at higher-than-average risk, consider the alternatives of soy, oat, cashew, and other non-dairy milks."
More than 11,800 men a year - or one every 45 minutes - are killed by the disease in Britain, compared with about 11,400 women dying of breast cancer. It means prostate cancer is behind only lung and bowel in terms of how many people it kills in Britain. In the US, the disease kills 26,000 men each year.
The study was published is in the American Journal of Clinical Nutrition.
