The Relationship Between Insulin and Cancer

Cancer is a complex and multifaceted disease, influenced by a wide array of genetic, environmental, and lifestyle factors. Among these, insulin, a hormone primarily known for regulating blood sugar levels, has emerged as a key player in cancer research. The relationship between insulin and cancer is multifactorial, involving metabolic pathways, cellular growth, and inflammation. 

Insulin is a hormone that is released by the pancreas when blood sugar levels are elevated. It pushes the glucose in the muscle and liver (much more so in the muscles). When you have a diet high in processed sugars, it takes more and more insulin to be secreted by the pancreas for your cells to respond. This is the essence of diabetes; insulin resistance. Insulin also is a builder, similar to an anabolic steroid. 

When insulin levels stay elevated as seen in insulin resistance, it can promote the growth of cancer cells. It can cause cancer cells to proliferate, and inhibit apoptosis (programmed cell death). This is due to insulin’s role in cell growth and division, as it can activate signaling pathways that are also involved in cancer progression.

Insulin also interacts closely with the insulin-like growth factor (IGF) system, which includes IGF-1 and IGF-2. These growth factors have similar effects to insulin and are involved in cellular growth and development. Elevated levels of IGF-1 are associated with an increased risk of several types of cancer, including breast, prostate, and colorectal cancer. Like insulin, IGF-1 promotes cell proliferation and inhibits apoptosis, contributing to tumor growth and cancer progression.

Elevated insulin can also cause chronic low-grade inflammation. Inflammation is a known risk factor for cancer, as it can create a microenvironment that promotes tumor development and progression. This, in turn, can lead to DNA damage and mutations, further increasing cancer risk. There is also a bit of a vicious circle effect that occurs. High insulin causes weight gain. Adipose tissue secretes pro-inflammatory cytokines making matters worse.

Conversely, there has been some research that suggests that medication for diabetes, such as metformin, can slow tumor growth. There are several proposed mechanisms. Metformin enhances insulin sensitivity and lowers blood glucose levels. It activates AMPK (AMP-activated protein kinase) which blocks the mTOR pathway. This pathway promotes cell growth and proliferation so when it’s blocked, it can suppress tumor growth. Metformin can also lower IGF-1. It may also promote apoptosis in cancer cells, blocking their proliferation. So it basically does the opposite of everything mentioned earlier in the article. This is not to say go get a prescription for metformin; rather that it’s just evidence that insulin resistance can be a key player in cancer development. 

So what to do? You know the answer. It’s all the diet and lifestyle choices. Sleep well, reduce stress, eat a whole foods diet, avoid high fructose corn syrup and processed foods, and exercise. These are all the things you need to do to stay insulin sensitive. 

References:

Algire C, Zakikhani M, Blouin MJ, Shuai JH, Pollak M. Metformin attenuates the stimulatory effect of a high-energy diet on in vivo LLC1 carcinoma growth. Endocr Relat Cancer. 2008 Sep;15(3):833-9. doi: 10.1677/ERC-08-0038. Epub 2008 May 9. PMID: 18469156.

Jiang, N. F. T., Liu, L. S., Zhang, S. H., et al. (2011). Type 2 diabetes and cancer risk: A systematic review and meta-analysis. Diabetes Research and Clinical Practice, 93(2), 118-126. https://doi.org/10.1016/j.diabres.2011.05.001