What Is Insulin, and Why Does it Matter?

by | Dec 14, 2021

Insulin is an essential hormone made by the pancreas. While most people only think about insulin when they think about diabetes, we all need insulin to survive. Insulin plays a central role in our body’s ability to process, use, and store energy. 

Insulin is a life-saver when you have the right amount at the right time. But too much insulin can pose a serious risk to both short-term and long-term health. Here’s what you should know about optimizing your body’s use of insulin to help you feel your best and keep your metabolism running smoothly.

The History of Insulin

Before we knew what insulin was, researchers in Germany began to view the pancreas as a vital organ. During scientific experiments in the late 1800s, the pancreas was removed from dogs which predictably led to the rapid and fatal onset of diabetes. Eventually, scientists pinpointed a specific type of pancreatic cell, called the islet of Langerhans, as the source of a crucial but mysterious biological substance. They named this substance after the Latin word for island, “insula.”

It wasn’t until 1922 that insulin was officially discovered through research at the University of Toronto. Fredrick Banting (an orthopedic surgeon), John Macleod (a physiology professor), J.B. Collip (a biochemist), and Charles Best (a student research assistant) successfully injected pancreatic extracts into canines, and eventually, humans, to observe the function of insulin first-hand. The team ultimately earned the Nobel Prize for their life-saving work isolating and dispensing insulin as a medical treatment.

People with type 1 diabetes (an autoimmune disorder that destroys the pancreas) need to take insulin medication because their bodies can’t make any insulin. Doctors relied on insulin sourced from pigs and cattle until the production of synthetic human insulin (Humulin) in 1982. Today, insulin comes in various pens and pumps with short or long-acting formulas. 

Gaining a deeper understanding of our body’s natural insulin regulation system offers hope for a world less burdened by obesity, type 2 diabetes, heart disease, certain cancers, infertility, Alzheimer’s and other hormonal or inflammatory health concerns. Here’s what insulin is doing in your body and how you can influence its effects for better health.

Insulin Sensitivity vs. Insulin Resistance

Just because we make insulin doesn’t mean it works well in our bodies. Having a “high sensitivity” to insulin means our cells are responsive to insulin. Insulin primarily helps transport glucose molecules from the bloodstream (blood sugar) and into the cells of muscle, body fat and the liver for processing. People who are sensitive to insulin maintain normal blood sugar levels efficiently. Digestion triggers insulin release, so the energy from food (broken down into glucose, amino acids and free fatty acids) can be burned, converted into storage, as glycogen or adipose tissue, or used to build and maintain muscle mass.

The opposite effect, an impaired insulin response, is called insulin resistance. Insulin resistance is an inflammatory condition that starts as prediabetes and can progress to type 2 diabetes. When cells are resistant to insulin, they have trouble converting food into energy. Insulin is unable to bring glucose and other nutrients into the cells. So instead, sugar and fatty acids build up in the blood. Elevated blood sugar levels can trigger more insulin release, promoting a self-perpetuating cycle of high insulin levels (hyperinsulinemia) and greater insulin resistance. Hyperinsulinemia hinders efforts to lose weight since insulin inhibits lipase, the enzyme responsible for burning body fat. Hints of insulin resistance can show up in various parts of the body.

On the skin, insulin resistance may cause necrobiosis lipoidica (small raised bumps that develop into yellow, red, or brown areas of swollen and hard skin), acanthosis nigricans (a dark, velvety band of skin on the back of the neck, groin, or armpit),  and digital sclerosis (tight, waxy skin on the hands, forearms, or upper arms). People with insulin resistance may also be more prone to blisters, breakouts, and skin infections. Not every skin issue is related to insulin, but your skin may be the first to show signs of a problem. Be sure to meet with a dermatologist to discuss any concerns and determine the root of any unexpected skin changes.

insulin resistance

Other potential signs and symptoms of insulin resistance include increased thirst and urination, blurry vision, and fatigue. Being overweight is also an established risk factor for insulin resistance. Perhaps more relevant than the number on the scale is the distribution of fat on the body. Research increasingly points to the importance of waist circumference for disease risk. Visceral (intra abdominal fat) and subcutaneous fat around the midsection appear to signal metabolic issues, like insulin resistance.

In addition, elevated blood sugars are hard on the body and can damage delicate nerves and organs, especially in the eyes, limbs, cardiovascular system, and kidneys. When left untreated, insulin resistance may produce long-term consequences, such as issues with memory and cognition.

Fortunately, dietary and lifestyle changes can slow down (and in some cases, reverse) the trajectory towards type 2 diabetes and further complications, especially when insulin resistance is identified early.

Eating Right for Insulin Sensitivity

Carbohydrates are often demonized because they cause a short-term rise in blood sugar. However, the intake of simple sugars (like white flour and corn syrup) versus unprocessed whole grains, fruits and vegetables has distinctly different effects on insulin sensitivity and glycemic control. There’s a strong consensus that avoiding refined sugar (especially from sugar-sweetened beverages) and consuming adequate dietary fiber are essential to prevent and treat type 2 diabetes. Furthermore, these nutritional changes support healthy weight loss, which significantly improves insulin sensitivity in overweight people.

Several dietary patterns have been evaluated for their effects on insulin resistance. For example, a 16-week randomized controlled trial of overweight adults with no history of diabetes demonstrated the benefits of a plant-based dietary intervention on insulin sensitivity and beta-cell function in the pancreas. Some of the most notable improvements in the plant-based group included a lower basal insulin level and a higher dose-response of insulin to glucose. Researchers did not impose any calorie restrictions, but the intervention group naturally consumed more carbohydrate and fiber and less total fat and protein than the control group (who made no changes to their usual diet).

Dietary patterns of high red meat and processed meats have been associated with the development of insulin resistance. While strict adherence to a vegan or vegetarian diet may not be necessary, replacing some of the meat in your diet with vegetarian sources like beans, nuts, and soy protein may be protective.

In addition, swapping saturated fats for polyunsaturated fats improved insulin sensitivity and lowered blood sugar levels in several studies. For example, data compiled in a wide scale review concluded that hemoglobin A1c levels improve by 0.1 percent for every 5 percent increase in polyunsaturated and monounsaturated fat calories. If the general population adopted this change, it could translate to a 22 percent lower incidence of type 2 diabetes.

Various micronutrients and trace minerals also influence insulin action, including calcium, iodine, iron and selenium. Deficiencies in zinc, chromium and magnesium have been identified in people with diabetes, but it’s not clear if these deficiencies contribute to or are a consequence of the disease. Studies also show that a vitamin D deficiency may lead to dysfunction of pancreatic cells and insulin-responsive tissues throughout the body. Therefore, taking dietary supplements may be beneficial if you have a known deficiency. But otherwise, choosing a varied, nutrient-rich diet can help ensure that most of your needs are met. It’s best to avoid high doses of supplements unless advised by your doctor since they may do more harm than good.

Other Risk Factors and Interventions

Reduce insuline resistance

Food directly affects insulin. But nutrition isn’t all that matters. Our sleep schedule, exercise habits, and stress management skills play significant roles in insulin response.

Sleep affects several hormones related to appetite, body weight, and insulin sensitivity. Studies indicate that insufficient sleep upregulates the hunger hormone ghrelin and suppresses satiety cues from leptin, leading to increased food intake, weight gain, and metabolic dysfunction. For instance, participants getting 5 hours of sleep for seven nights in a row impaired insulin sensitivity. Similar findings were confirmed in trials with 14 days of 5.5 hours of sleep and four days of 4 hours of sleep per night.

The benefits of exercise on insulin and glucose regulation have been demonstrated in multiple studies. While aerobic training appears to enhance insulin sensitivity and beta-cell function, resistance training helps increase the amount of muscle mass available for glucose uptake. Furthermore, exercise is a positive outlet for stress which is independently associated with inflammation and insulin resistance.

Unfortunately, some people are at a higher risk of insulin resistance, even when living a healthy lifestyle. For example, people of African American, Asian American, Pacific Islander American, Hispanic, Native Hawaiian, Native Alaskan, or American Indian heritage have a greater likelihood of insulin resistance. Being over age 45 or getting diagnosed with a hormonal disease, like polycystic ovary syndrome (PCOS), acromegaly, or Cushing’s syndrome, also increases your risk. In addition, some medications cause insulin resistance as a side effect, including steroids, HIV medications, and antidepressants.

If you’re in a high-risk group, have a history of gestational diabetes or PCOS, or have a strong family history of diabetes, ask your healthcare provider about appropriate screenings and ways to monitor for signs of insulin resistance. Depending on your current health, your doctor may recommend medication to boost insulin sensitivity, like metformin. In addition, meeting with a sleep specialist, dietitian, exercise physiologist, or therapist can give you extra support in the fight against insulin resistance.

 

References

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