Is There Any Relationship Between Insulin and Cancer?

The researchers then looked at the relationship between daily insulin doses and the incidence of cancer. They noted that higher insulin doses were associated with an increase in the number of cancer cases, which was significantly higher among participants who used high insulin doses compared to those who used low doses.

However, the number of participants was too small, and the number of cancer cases was proportionately too low to confirm a relationship between daily insulin doses and the incidence of cancer. For the same reasons, the particular types of cancer concerned could not be identified.

Complex mechanisms

This finding is not, however, unique to people with T1D. Since insulin is a hormone that is naturally secreted by the body (except for people with T1D who need to administer it), it’s interesting to note that other studies have observed the same phenomenon among people without diabetes who had high blood insulin levels for various reasons (e.g., obesity, aging, sedentary lifestyle, insulin resistance). 

According to some studies, high blood insulin levels combined with insulin resistance could promote the development or progression of cancer. Insulin is a hormone that supports the storage of nutrients and the development of cells, some of which can sometimes, unfortunately, evolve into cancer.

The chronic inflammatory process (article in French only) involved in T1D might also play a role by increasing the quantity of insulin needed. So, could this mean that the risk of cancer is associated with the degree of inflammation rather than with the insulin dose itself?

Since there are numerous risk factors (e.g., excess weight, sedentary lifestyle) and since the mechanisms involved in the development of cancer are complex, we can hardly conclude from this new study that high insulin doses increase the risk of cancer.

Can the required insulin dose be reduced?

First of all, it’s important to note that each person is different and has different insulin needs and a different risk of developing certain cancers. And some factors (such as genetic ones) cannot be changed.

If you have T1D and have concerns about your insulin doses, don’t hesitate to talk to the members of your healthcare team, who can help you to assess the situation and identify solutions. 

Here are a few strategies that can help to increase the efficacy of your insulin and decrease your required dose:

• Make the most of technology. Some technologies like hybrid closed loop systems can help you to administer insulin doses that are closer to your actual needs, through the automated adjustment of certain settings and continuous glucose monitoring.
• Try to decrease hypoglycemic episodes. After correcting low blood sugar, you may very well need to take insulin to treat high blood sugar (hyperglycemia). In addition, the carbs you will eat to correct your hypoglycemia can lead to weight gain, which will decrease insulin efficacy. Continuous glucose monitors (e.g., Dexcom, FreeStyle Libre) that allow you to set alarms (before/upon hypoglycemia) are excellent tools to limit hypoglycemic episodes. Some types of insulin can also decrease the risk of hypoglycemia.
• Practise regular physical activity (article in French only).
• Improve the quality of your diet (e.g., limit processed, high-carb and high-fat foods).
• Avoid injecting insulin into lipodystrophies (video in French only).
• Find stress-reducing strategies.
• Talk to your healthcare team. There are certain medications typically used for T2D that can sometimes be combined with insulin.

To summarize, there are many factors that can impact the onset of cancer. Further studies will be needed to ascertain whether there really is a relationship between insulin doses and cancer prevalence, and to better understand the underlying mechanisms. However, this study encourages us to think about strategies for decreasing the quantity of insulin needed by people with T1D who use high doses, while not losing sight of blood sugar control objectives.

References :

• Zhong W, Mao Y. Daily Insulin Dose and Cancer Risk Among Patients With Type 1 Diabetes. JAMA Oncol. Published online July 28, 2022. doi:10.1001/jamaoncol.2022.2960
• Carstensen, B., Read, S.H., Friis, S. et al. Cancer incidence in persons with type 1 diabetes: a five-country study of 9,000 cancers in type 1 diabetic individuals. Diabetologia 59, 980–988 (2016). https://doi.org/10.1007/s00125-016-3884-9
• Major JM, Laughlin GA, Kritz-Silverstein D, Wingard DL, Barrett-Connor E. Insulin-Like Growth Factor-I and Cancer Mortality in Older Men. J Clin Endocrinol Metab. 2010 Jan 15.
• Roddam AW, Allen NE, Appleby P, Key TJ, Ferrucci L, Carter HB, Metter EJ, Chen C, Weiss NS, Fitzpatrick A, Hsing AW, Lacey JV Jr, Helzlsouer K, Rinaldi S, Riboli E, Kaaks R, Janssen JA, Wildhagen MF, Schröder FH, Platz EA, Pollak M, Giovannucci E, Schaefer C, Quesenberry CP Jr, Vogelman JH, Severi G, English DR, Giles GG, Stattin P, Hallmans G, Johansson M, Chan JM, Gann P, Oliver SE, Holly JM, Donovan J, Meyer F, Bairati I, Galan P. Insulin-like growth factors, their binding proteins, and prostate cancer risk:analysis of individual patient data from 12 prospective studies. Ann Intern Med. 2008 Oct 7;149(7):461-71, W83-8.
• Godsland, Ian F. “Insulin resistance and hyperinsulinaemia in the development and progression of cancer.” Clinical science (London, England : 1979) vol. 118,5 315-32. 23 Nov. 2009, doi:10.1042/CS20090399