Michelle Holmes Study: Milk, Pregnancy May Affect Cancer Risk (BWH:HMS)

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Milk, Pregnancy May Affect Cancer Risk, Study Says

Tuesday, September 10,12:09 AM ET

 

WASHINGTON (Reuters) - Pregnancy may lower a woman's risk of cancer but drinking

milk could raise it, researchers reported on Tuesday.

 

Both factors, as well as the use of hormone replacement therapy, affect levels

of a hormone that may influence the development of some cancers, a team at

Brigham and Women's Hospital and Harvard Medical School ( news - web sites) in

Boston found.

 

The finding could explain why women who have had children have a lower risk of

cancer -- something doctors have noticed but been unable to explain, Dr.

Michelle Holmes, who led the study, said.

 

Pregnancy, HRT use, and milk drinking all affect levels of insulin-like growth

factor 1 or IGF-1, a hormone linked to an increased risk of cancer, Holmes and

colleagues report in the journal Cancer Epidemiology Biomarkers & Prevention,

which is published by the American Association for Cancer Research.

 

" This is the first study to report that the more pregnancies a women had, the

lower was her blood level of IGF-1, " Holmes said.

 

" Pregnancy is known to protect against several cancers such as breast and colon

cancer. It is possible that the mechanism of this protection could be through

lowering IGF-1 levels. "

 

Women who had four or more pregnancies had IGF-1 levels that were on average 15

percent lower than in women who had never been pregnant, the researchers found.

 

Using data from a large, long-term study of more than 1,000 nurses who record

their diets carefully and who are then watched for changes in health, Holmes'

team also found that those who drank the most milk had higher levels of IGF-1.

 

IGF-1 is important to the growth and function of many organs, but higher levels

have been associated with an increased risk of prostate, colon, lung and breast

cancer ( news - web sites).

 

" We concluded that greater milk consumption was associated with higher levels of

IGF-1, " said Holmes. " This association raises the possibility that diet could

increase cancer risk by increasing levels of IGF-1 in the blood stream. However,

more research must be done to determine whether milk consumption itself is

directly linked to cancer risk. "

 

The role of HRT and cancer is less clear -- it can raise the risk of breast

cancer, for instance. But Holmes's team found that women who were taking

estrogen after menopause had the lowest levels of IGF-1, followed by women using

oral estrogen plus progesterone.

 

This may explain why HRT reduces the risk of colon cancer, Holmes said.

 

Now more research needs to be done to find out why this does not counteract

the effect of HRT on breast cancer, Holmes said.

 

 

 

 

 

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