Researchers from the Albert Einstein College of Medicine in New York City have said that data has shown that women with higher than normal insulin levels have a higher risk of developing breast cancer than those with lower insulin levels.

The research was led by Dr. Marc J. Gunter at Albert Einstein College of Medicine in the Bronx, New York, to study an association between blood parameters and breast cancer. The researchers studied postmenopausal women participating in the Women's Health Initiative Observational research and compared their insulin levels of 835 women who developed breast cancer and 816 women who did not.

The study found that those whose fasting counts were the highest had a 46% increased risk of breast cancer as compared to women with lowest fasting insulin levels. In the case of women who were not on hormone replacement therapy (HRT) the risk was even greater and among them the women with the higher insulin levels had a 2.4 times greater chance of developing breast cancer than the lower insulin level participants. Fasting levels of estrogen were also linked with 59 % higher risk among women with the highest versus the lowest estrogen levels.

According to the American Cancer Society higher levels of insulin have been shown to stimulate the growth of breast cells and obesity has been linked to an increased risk of breast cancer.

"These data suggest that hyperinsulinemia [excess insulin in the blood] is an independent risk factor for breast cancer and may have a substantial role in explaining the obesity-breast cancer relationship," the researchers wrote.

The study was reported in the Journal of the National Cancer Institute.