- Insulin is a hormone secreted by the pancreas that allows glucose to move out of the bloodstream and into cells for energy.
- Insulin is an anabolic hormone that stimulates growth pathways, such as glycogenesis and lipogenesis.
- A diet high in processed carbohydrates and sugars causes abnormally increased insulin production. Over time, this can cause the cells to reject insulin and lead to insulin resistance.
- To regulate insulin production and sensitivity it is beneficial to minimize added sugars, focus on food quality, monitor overall protein intake, and to minimize grazing behaviors.
The hormone insulin has turned into quite the buzzword lately. Ask anyone slightly interested in health about insulin and they will likely report that it is driving all of their health problems. There is no doubt that insulin is a critically important hormone involved in metabolism, weight maintenance, and glucose control, along with many other functions. Today we will take a deep dive into insulin’s normal functions, factors that can interfere with normal insulin action, and strategies for optimizing insulin levels and insulin sensitivity.
One of insulin's primary functions is to regulate glucose levels, keeping them in a tight, physiologically normal range. When glucose starts to rise for any reason, insulin gets released from the beta cells of the pancreas and functions as a “key” for moving glucose out of the bloodstream and into our cells to be utilized for energy.
To put it simply, when our glucose levels rise, so do our insulin levels. The primary stimulant for glucose to increase is eating, particularly foods rich in carbohydrates (although despite popular belief, protein also stimulates insulin release). After a meal containing carbohydrates and/or protein, your body will break down the nutrients from that meal into glucose for your cells to use as energy. These glucose molecules are essentially useless when they are in the blood. It is insulin’s job to signal that the glucose should leave the bloodstream and enter a cell.
When there is an abundance of energy and the cells do not need additional fuel (such as after eating a large meal or when energy expenditure is low), insulin will divert the glucose energy towards longer-term reserves that the cells can tap into on a future date. This first back-up storage form is glycogen, which is located in the liver and the muscles. Glycogen can be thought of as a wallet, easy to pull out some spare cash but with finite storage space. A longer-term back-up energy storage site is our fat reserves, which can be thought of as a bank account. It is harder to access, but has unlimited room for storage. If our glycogen levels are saturated, insulin will direct the resources to create fat in order to save that extra energy for a “rainy day.” Insulin will essentially try to place the glucose and energy wherever it needs to go in order to get it out of the bloodstream.
Insulin is categorized as an anabolic hormone, meaning when insulin is released it will stimulate various growth pathways. As we have learned, this can include growth in glycogen storage and/or fat cells. This also includes aiding in muscle growth, cell repair, and other building functions. When levels of circulating insulin are low, catabolic reactions are stimulated and growth pathways are inhibited, causing a switch to functions such as fat breakdown and energy preservation. So while it is absolutely crucial to assure we do not always have high levels of insulin circulating, insulin also serves many useful daily functions.
With such as tightly regulated system, how can things go awry? If our body is constantly sending signals for insulin to be released (such as from a diet high in processed carbohydrates and sugars, or a pattern of constant eating) circulating insulin levels start to enter supraphysiological levels. This can lead to hyperinsulinemia, simply meaning abnormally high levels of insulin in the blood. When our cells are constantly being exposed to high levels of insulin, they start to “ignore” the effects of insulin even though there is plenty of it available, leading to what is called insulin resistance. The glucose is then rejected from the cells, remaining in the bloodstream and leading to elevated blood glucose levels. Because the glucose never leaves the blood, the pancreas never flips the “off switch” and continues to produce more and more insulin.
Excess insulin in the blood leads to elevated and prolonged glucose levels. The body responds by slowing fat breakdown and diverting more energy into fat cell production. Elevated blood insulin levels also signals the sensation of hunger, resulting in increased carbohydrate and sugar cravings. It is a vicious cycle that can be hard to break.
High levels of insulin and insulin resistance tends to be one of the first abnormalities that can then lead to a dysfunctional metabolic system and chronic disease, such as diabetes and cardiovascular disease. With such serious consequences, how can we fix the problem?
- Minimize processed carbohydrates and sugar. The most obvious way to mitigate the potential downslide of insulin resistance is to keep your intake of refined carbohydrates, such as flour based items, packaged snack foods, and added sugars, to a minimum. If your food comes with a nutrition label, double check the ingredients list to assure sugar has not been snuck in. As much as possible, focus on only eating whole foods with minimal processing. These foods take longer for our bodies to process, leading to a smaller glucose spike and therefore a smaller insulin response.
- Avoid grazing. Another driver of elevated insulin levels is snacking between meals. Each small snack leads to a peak in insulin production. If you are always grazing between mealtimes, your body will constantly be producing insulin. Practice small fasts between meals and give your body a chance to reduce the peak in insulin production before your next meal.
- Look at the whole picture. There is not a single cause of insulin resistance, but rather a compounding of several factors that constantly increase insulin levels. Additional factors that can compound onto each other are chronic inflammation, disrupted circadian rhythms, chronic stress with elevated cortisol, and lack of physical activity/movement which affects mitochondrial biogenesis, skeletal muscle glucose uptake and insulin sensitivity. Don’t neglect sleep, stress management, and regular exercise in your lifestyle.
- Keep protein intake in check. Although carbohydrates are the largest driver for insulin release, protein also stimulates insulin. Studies have shown that some protein items increase insulin to equal levels as white bread. It is important to have adequate dietary protein each day, but too much can have a negative impact on circulating insulin levels.
In summary, insulin is a hormone that requires balanced eating and appropriate lifestyle choices to manage. It plays an essential function and we could not live without it (e.g. type 1 diabetics need to inject insulin to survive since they do not produce insulin naturally). Nevertheless, we want to be careful to avoid an overproduction of insulin. A diet high in refined carbohydrates, added sugars, excessive protein, grazing pattern of eating, and/or inactivity can cause a dysregulated insulin response, contributing to insulin resistance and weight gain. While many other scenarios stimulate insulin release, the primary stimulant is elevated glucose levels. So, anything that can lower glucose will also help keep our insulin levels in check. Optimizing our dietary patterns and incorporating healthy lifestyle changes can make a profound impact on insulin regulation and sensitivity. We will discuss these factors more in later education segments.