Tuesday Feb 17, 2015 (foodconsumer.org) -- A new study in Growth Hormone & IGF Research suggests that cancer patients may want to cut their intake of total protein to slow the tumor growth.

The study of 1883 postmenopausal women in UK shows that subjects in the highest quintile of total protein and dairy protein intakes had 7.6% and 5.5% higher serum insulin like growth factor (IGF-I) concentrations, respectively, compared with those in the lowest quintile.

Higher circulating concentrations of IGF-I have already been associated with an increased risk of cancers such as breast cancer, implying that high IGF-I can promote the development of cancer.

The study also found heavy alcohol drinking (>14 drinks per week) was actually linked to 8.8% lower IGF-I, compared with 3 to 7 drinks per week.   Alcoholic beverages have been recognized as a probable human carcinogen because evidence indicates that it promotes the development of cancer.

Also current hormone therapy users were found to have 9.9% lower IGF-I, compared with non-current hormone users.  Hormone therapy is a known risk factor for certain cancers.

If IGF-I is the fuel for the cancer development, these study findings seem to suggest that heavy alcohol drinking and hormone therapy may lower cancer risk, which is contradictory to the current opinion about the promotional effect of alcohol and hormones on the cancer development.

It is clear that high protein intake is not good for health.  Currently, Americans have intake of greater than 15% of total calories from proteins, mainly animal proteins such as dairy protein.   Colin T. Campbell, Ph.D., a Cornell University nutrition professor suggests in his book China Study that the protein intake should be controlled around 11% for adults and also protein from plants should be preferred. (David Liu, PHD)

Kathryn E. Bradbury, , Angela Balkwill, Sarah J. Tipper, Francesca L. Crowe, Gillian K. Reeves, Jane Green, Valerie Beral, Timothy J. Key,  The association of plasma IGF-I with dietary, lifestyle, anthropometric, and early life factors in postmenopausal women, Growth Hormone & IGF Research, Volume 25, Issue 2, April 2015, Pages 90–95.