Meat and dairy products may increase risk of prostate cancer

MEAT and dairy products may increase the risk of prostate cancer by raising levels of a cell-growth hormone.

Scientists have found a significant association between blood levels of Insulin-like Growth Factor-1 (IGF-1) and the likelihood of men being diagnosed with the disease.

For those in the top fifth of the normal range the risk went up 40%, compared with those at the bottom end of the scale.

Previous studies have shown that IGF-1 levels are higher in individuals who consume a lot of meat, milk, butter and cheese.

Strict vegetarians have less of the hormone.

A link between IGF-1 and prostate cancer has been suspected before, but evidence has been lacking.

By combining results from 12 separate blood sample studies, the researchers were able to identify the trend more clearly.

The scientists pooled data from a total of 3,700 men with prostate cancer and 5,200 without the disease.

Blood samples were taken on average when cancer patients were 62 years of age, five years before diagnosis.

Study leader Dr Andrew Roddam, a cancer research UK epidemiologist at Oxford University, said: “What we found was a modest association at best, but it was statistically significant. A lot of the individual studies found the same trend but were too underpowered for their results to be reliable.”

IGF-1 is a protein hormone that spurs on cell division and is important for the growth and development of young children and adolescents. In adults it regulates cell growth and death, and normal levels are necessary for good health.

However, the growth factor has certain effects that are thought to encourage cancer. Notably it inhibits programmed cell death, or apoptosis, which is one the main ways the body rids itself of potentially dangerous damaged cells. Without this, cells with damaged DNA may trigger cancer.

The degree to which a meat or dairy diet increases IGF-1 level is unclear.

“It could be about 10% to 15% higher in people who have a high consumption of dairy products or meat,” Dr Roddam said.

Dr Roddam stressed that all the study participants fell within the normal range for blood concentrations of the hormone. But the high end group had about twice as much IGF-1 in their blood as those at the low end.

The findings are published in the journal Annals of Internal Medicine.

Data from the National Cancer Registry of Ireland revealed 2,406 new cases of prostate cancer were diagnosed here in 2005

Dr Roddam said: “There is a need to identify risk factors for prostate cancer, especially those which can be targeted by therapy and/or lifestyle changes. Now we know this factor is associated with the disease we can start to examine how diet and lifestyle factors can affect its levels and whether changes could reduce a man’s risk.

“But it’s important to point out that there is no evidence to suggest that measurement of IGF-1 levels could be used to develop new prostate screening methods. Other studies have shown that existing methods of detecting prostate cancer are not improved by also measuring IGF levels.”

Scientists are already investigating ways to block IGF-1’s ability to stimulate tumour growth, he said.

There is conflicting evidence from other studies that the hormone may be associated with breast and bowel cancer.