By Jimmy Downs

Friday Oct 2012 (foodconsumer.org) -- Having type 2 diabetes mellitus can be a risk factor for breast cancer, according to a new meta-analysis published in Endocrine-related Cancer.

P.J. Hardefeldt of The University of Sydney, Penrith, Australia and colleagues set out to meta-analysed data from a few dozens of epidemiological studies to see how diabetes mellitus would be associated with the risk of breast cancer in both men and women.

People with type 2 diabetes mellitus have high insulin levels (hyperinsulinaemia), which is known to have a proliferative effect to promote cancer growth.  This connection prompted researchers to conduct this meta-analysis.  

(When insulin is produced, insulin like growth factor 1 is also produced and the latter is known to promote the growth of cells including cancer cells).

The researchers searched the major databases including MEDLINE, EMBASE, PubMed, Current Contents Connect and Google Scholar and other references and found 41 relevant studies including 38 investigating breast cancer in women and 5 investigating breast cancer in men.

Overall,  women who had diabetes mellitus were 24 percent more likely to develop breast cancer whereas men who had diabetes mellitus were 40 percent more likely to develop breast cancer, compared to those who did not have diabetes.

Type 2 diabetes mellitus was associated with 22 percent increased risk for breast cancer and gestational diabetes was not.  This can be because gestational diabetes is in many cases only associated with pregnancy only meaning that patients would not have to expose themselves to high levels of insulin for a long period.

Additionally, type 1 diabetes mellitus was not associated with risk of breast cancer either, which should not be surprising because type 1 diabetes patients often have low levels of insulin.

The researchers conclude "diabetes increases the risk of breast cancer in both women and men. This association is confirmed in women with type 2 diabetes and supports the hypothesis that diabetes is an independent risk factor for breast cancer."

An estimated 26 million Americans live with diabetes mellitus and about 230,000 women are expected to be diagnosed with breast cancer in 2012 in the U.S. and the cancer will kill about 37,000 women in the same year and the same country, according to the National Cancer Institute.

Breast cancer in many cases can be prevented.  According to an authoritative organization, two major risk factors that are known for sure to cause breast cancer and that women need by all means to avoid are hormone therapy and medical radiation.

On the other hand, taking some dietary supplements may help reduce the risk of breast cancer.  One remarkable dietary supplement can be vitamin D, which according to researchers at University of Southern California helps prevent vitamin D deficiency, which is related to 75 percent cases of breast cancer, according to studies.  For that reason and others, some researchers argued that taking vitamin D supplements or by whatever means to avoid vitamin D deficiency, breast cancer risk can be reduced by 75 percent.