What is Insulin and why we should keep its levels as low as possible
The human body contains many hormones. When it comes to hormones we often think of testosterone in men that helps build muscle, oestrogen for the development and regulation of the female reproductive system. Insulin however has received mixed press. In the medical and scientific community, it is well known as it is associated with Type 1 and 2 diabetes. It turns out that insulin is the most important hormone and your life depends on it. As we age there is an increase susceptibility to chronic diseases such as cardiovascular diseases. A large cause of that is due to high levels of insulin, a term more commonly referred to as insulin resistance.
How does it work?:
Insulin is produced in the pancreas. More specific it is synthesized in the beta cells of the pancreas. After a meal rich in carbohydrates or even protein, the large starch chain begins to be broken down and the levels of glucose begin to rise. Since high levels of glucose in the blood is toxic, insulin is secreted. Some of the glucose is used immediately and the rest will either be converted into glycogen for short term storage or insulin can dispose it into adipose tissue (or fat) for long term storage.
Insulin and Metabolic Syndrome:
The hallmark of the Western diet is the frequent consumption of refined grains/starches and sugar. This style of eating causes glucose levels in the blood to skyrocket leading to a large increase in insulin. Continuously high glucose levels or glucose spikes following a meal puts a lot of pressure on the pancreas. In the long term this can lead to the development of insulin resistance. Being insulin resistant puts you at risk of developing a wide range of health conditions including heart diseases.
High levels of insulin, a term referred to as Hyperinsulinemia is an Independent Risk Factor for Ischemic Heart Disease (Després et al., 1996). In this study men with the lowest levels of fasting insulin, were protected from heart diseases. Logistic regression showed that insulin concentration remained associated with heart diseases, even when other factors were taken into account ((Després et al., 1996).
Insulin is an anabolic hormone which causes tissue growth. In fact high levels of insulin or insulin resistance along with high visceral fat leads to a six fold increase in developing colon cancer (Yamamoto et al., 2010).
Insulin and ageing
Studies in mice have shown that when the levels of insulin are reduced the mice have on average a 25% increase in their lifespan (Templeman et al., 2017). An interesting study by Paolisso showed that centenarians have similar insulin levels to healthy adults (Paolisso et al., 1996). The biological mechanism by which Insulin accelerates ageing is by activating the mammalian target of Rapamycin (mTOR) (Yoon, 2017).
How to reduce insulin? The low insulin lifestyle
The easiest why is to embrace a diet that is on the low side of carbohydrates with periodic periods of fasting. That does not mean following a keto diet. In fact, whole grains such as sweet potatoes, quinoa and buckwheat should be eaten regularly. Embracing intermittent fasting can help to deplete glycogen stores and thus lower insulin. Physical activity in the form of high intensity training and strength training should also be carried out regularly. All these factors will help improve insulin sensitivity.
Written by: Federico Bernuzzi: BSc in Biochemistry, MSc in Epidemiology and Biostatistics 2nd year PhD in Molecular Nutrtion
References:
Després, J.-P., Lamarche, B., Mauriège, P., Cantin, B., Dagenais, G. R., Moorjani, S., & Lupien, P.-J. (1996). Hyperinsulinemia as an Independent Risk Factor for Ischemic Heart Disease. New England Journal of Medicine, 334(15), 952–958. https://doi.org/10.1056/NEJM199604113341504
Paolisso, G., Gambardella, A., Ammendola, S., D’Amore, A., Balbi, V., Varricchio, M., & D’Onofrio, F. (1996). Glucose tolerance and insulin action in healty centenarians. American Journal of Physiology-Endocrinology and Metabolism, 270(5), E890–E894. https://doi.org/10.1152/ajpendo.1996.270.5.E890
Templeman, N. M., Flibotte, S., Chik, J. H. L., Sinha, S., Lim, G. E., Foster, L. J., … Johnson, J. D. (2017). Reduced Circulating Insulin Enhances Insulin Sensitivity in Old Mice and Extends Lifespan. Cell Reports, 20(2), 451–463. https://doi.org/https://doi.org/10.1016/j.celrep.2017.06.048
Yamamoto, S., Nakagawa, T., Matsushita, Y., Kusano, S., Hayashi, T., Irokawa, M., … Mizoue, T. (2010). Visceral Fat Area and Markers of Insulin Resistance in Relation to Colorectal Neoplasia. Diabetes Care, 33(1), 184–189. https://doi.org/10.2337/dc09-1197
Yoon, M.-S. (2017). The Role of Mammalian Target of Rapamycin (mTOR) in Insulin Signaling. Nutrients, 9(11), 1176. https://doi.org/10.3390/nu9111176
