Too much insulin & breast cancer

Insulin is important for the regulation of blood sugar in our body. People who are obese have a higher incidence of developing type II diabetes. Although these individuals have a higher level of insulin in their blood, the blood sugar is still elevated because the cells in the body are ‘resistant’ to the insulin action. Obese women are known to have a higher incidence of breast cancer. The higher oestrogen level in these women has been shown to play a significant role in causing breast cancers. Does the excess insulin in these obese women play a role too?

Researchers from US assessed the association between circulating insulin level and the risk of breast cancer in non-diabetic women (J Natl Cancer Inst 2009; 101: 48 – 60). Women enrolled in the Women’s Health Initiative Observational Study (WHI-OS) were studied: 835 women with incident breast cancer and 816 women without breast cancer. Women with the highest insulin levels, when compared to those with the lowest levels, were 46% more likely to develop breast cancer. Among women who did not use hormonal therapy (HT), the risk of developing breast cancer in women with the highest vs lowest insulin levels was increased 2.4 times. Obesity (where BMI ≥ 30), among non-HT users, was also associated with the risk of breast cancers. If your BMI is ≥ 30, your risk of developing breast cancer is 2.12 times more than someone whose BMI is 18.5 to < 25.

In laboratory studies, insulin has been shown to be a mitogen. (A mitogen is a factor which can cause cells to divide.) The above study showed that too much insulin exerts a deleterious effect on breast tissue. Obese individuals, both men and women, have higher circulating levels of oestrogen and insulin. In women, elevated levels of oestrogen and insulin are thought to be responsible for the increased breast cancer risk. In men, the elevated oestrogen and insulin levels have not been linked with specific cancers yet. However, it would not be unreasonable to speculate that it is only a matter of time before a causal relationship with some cancer is found.

This is the beginning of a new year and traditionally it is time to make a resolution. Many have made unrealistic goals and thus fail to fulfill their wishes. Losing weight should be done gradually. If you go on a crash course, starve yourself and lose 3 kg over a week, the bulk of the weight loss would be from muscle. When you put on weight later on, the gain is more in the form of fat.

As this is the start of a new year, do start with your resolution but do not be impatient. Losing weight and staying trim requires a long term commitment. Like many good things in life, it takes time.