(This is one of three Health Insight blogs based on the three parts of Dr Benjamin Bikman’s book: Why we get sick. The three blogs are: INSULIN RESISTANCE AT THE ROOT OF MOST CHRONIC DISEASES, INSULIN RESISTANCE CAUSES, and INSULIN RESISTANCE CURES.)
Insulin resistance is an epidemic most people have never heard of and the overwhelming majority of people with insulin resistance are unaware that they have this condition. It is estimated that more than half of the populations in America, China, and India are known to be insulin resistant, and that 80% of individuals with insulin resistance live in developing countries.
The role of insulin in the body:
Insulin is a hormone made in the pancreas and is well known for regulating our blood glucose levels. (Blood glucose is the more accurate term, rather than the commonly used blood sugar.) Glucose comes from the carbohydrates in the food we eat, as carbohydrates get converted into glucose during the digestive process and then get absorbed into the bloodstream.
When we eat food that increases blood glucose levels, the pancreas releases insulin into the bloodstream, where it acts as the key which opens the doors of cells to escort glucose from the bloodstream into the cells. Glucose acts as fuel to produce energy in cells. In this way insulin lowers and regulates blood glucose levels to keep it in the normal range.
The specific effect of insulin depends on the type of cell, for example, when insulin binds to a liver cell it makes fat (among other things) and when binding to a muscle cell it makes new proteins (among other things).
What is insulin resistance?
Insulin resistance refers to a reduced response by cells to the hormone insulin. Various conditions can cause a cell to stop responding to insulin, making the cell insulin resistant. As more cells become insulin resistant, the body is considered insulin resistant.
For various reasons the harmony in which all the biochemical processes in the body work can be disturbed, affecting the efficient functioning of the body. In the case of insulin, the cells in the muscles, fat and liver may stop responding well to insulin and become resistant to the door opening effect of insulin for the absorption of glucose. This results in a build-up of glucose in the bloodstream, which prompts the pancreas to secrete more insulin to help glucose enter the cells. Should the pancreas secrete enough insulin to overcome the weak response of cells to insulin, blood glucose levels will remain in the normal healthy range. When insufficient insulin for the amount of glucose in the bloodstream is secreted, the build-up of glucose remains in the bloodstream instead of entering the cells. Over time this can lead to prediabetes and type 2 diabetes.
Compensating for insulin resistance by an increase in insulin release is effective only temporarily. As insulin resistance increases, impaired glucose tolerance develops. Ultimately, exhaustion or failure of the pancreatic insulin producing cells results in a relative decrease in insulin production and secretion.
Sugar spikes – the main cause of insulin resistance:
Blood sugar spikes occur when your blood sugar first rises and then falls sharply after you have eaten certain types of food. Unhealthy refined carbs have a high glycaemic index, which means fast digestion, coupled with rapid glucose absorption, to create spikes of high blood sugar (glucose) levels. A regular diet that is high in high-carb foods, and low in blood sugar balancing nutrients such as protein and fibre, results in higher than usual insulin levels as the body tries to lower blood sugar levels. When consuming too much high-glucose foods, too often, cells lose their sensitivity to insulin.
Uric acid from sugar – contributing to insulin resistance:
A single molecule of sugar consists of equal amounts of glucose and fructose, which gets separated early during the digestive process in the small intestine. After separation, they follow different pathways in the body and have different effects when metabolized. About 80% of glucose circulates in the bloodstream and around 20% goes to the liver, while 100% of fructose goes straight to the liver, where it goes through various steps during metabolism, ending up as uric acid.
When liver cells are flooded by excess amounts of fructose, most of this excess is converted to fat, called triglycerides. A build-up of fat can result in insulin resistance in the liver. In addition, high levels of uric acid compromise the way insulin works and can contribute to insulin resistance throughout the body, including the brain.
Insulin resistance and heart health:
Insulin resistance and cardiovascular disorders (various conditions that affect the heart and blood vessels) are viewed as almost inseparable, as there is no single variable more relevant to heart disease than insulin resistance.
Insulin resistance affects blood vessel walls in three ways:
- Insulin resistance and high insulin levels increase blood pressure, resulting in the likelihood of damage to blood vessels.
- Insulin resistance increases lipid deposition (plaque) in blood vessel walls, primarily as higher insulin levels result in the liver producing more of the dangerous smaller, denser LDL cholesterol molecules, which are prone to get stuck in blood vessel walls.
- Insulin resistance increases inflammation in blood vessel walls. Normal levels of insulin have an anti-inflammatory effect, while high levels of insulin activate inflammation in insulin resistant people.
Insulin resistance compromises the heart’s ability to take in and use glucose, causing the heart to suffer from a relative lack of energy and nutrients, leading to the reduced ability of heart muscles to contract and pump blood normally.
Insulin resistance affects the brain and causes neurological disorders:
As recently as 20 years ago the brain was deemed to have no response to insulin, but research has since revealed that brain cells (neurons) have insulin receptors, and that insulin regulates many processes in the brain. Insulin stimulates neurons to take up glucose for fuel. It also plays a role in regulating our appetite – when the brain senses increased insulin in the body after a meal, our appetite will wane.
The brain can become insulin resistant concurrently with the rest of the body and normal brain function can become impaired, such as leading us to overeating, which contributes to weight gain, as well as compromising short term learning and possibly damaging long-term memory.
Insulin resistance can inflict profound harm on brain physiology and contribute to dementia, of which Alzheimer’s disease is the most common form of dementia. Alzheimer’s is a very complicated disorder with many mechanisms involved. Research has shown that insulin resistance contributes to such an extent to Alzheimer’s that this disease is referred to as type 3 diabetes by some scientists.
The neuropathological hallmarks of Alzheimer’s disease are tau protein tangles and beta-amyloid plaque, which have been linked to impairment in brain insulin signaling. Normal insulin signaling in the brain inhibits the activity of tau. When this signaling is compromised due to insulin resistance, tau becomes overactive, potentially leading to tau neurofibrillary tangles. In the case of beta-amyloid plaque, which accumulates in the spaces between brain cells, high levels of insulin increase the release of beta-amyloid from brain cells, which increases its accumulation outside and between brain cells.
In addition, as the brain becomes progressively insulin resistant, it becomes less and less able to obtain sufficient glucose to meet its energy requirements, resulting in a brain that doesn’t work as well as it should. This decline follows the pattern of “less brain insulin sensitivity – less brain glucose uptake – less brain energy – compromised brain function.”
As insulin resistance affects blood vessel function, the brain may suffer from insufficient blood flow, leading to a disorder called vascular dementia.
Many people with Parkinson’s disease (also a brain disorder) develop dementia as the disease progresses, due to a large extent to the loss of dopamine-producing brain cells. Insulin is known to alter dopamine in the brain and studies found that the most insulin resistant people have the lowest production of dopamine in their brains.
A healthy brain requires healthy insulin sensitivity.
Insulin resistance and reproductive health:
As insulin is the king of all metabolic hormones, it is a strong indicator of metabolic health in the body. Normal levels of insulin reflect good metabolic health and normal levels of insulin promote normal fertility in ovaries and testes.
Insulin is essential for normal reproduction, as it acts as a signal to tell the brain whether the environment in the body is metabolically safe. Normal insulin levels indicate that the potential parent is healthy, and their diet is sufficient to grow a fetus and raise a newborn.
Insulin resistant men and women are more likely to be infertile than their insulin-sensitive counterparts
Insulin resistance and cancer:
Cancer is one of the most dreaded diseases of our time and the second leading cause of death worldwide behind cardiovascular diseases. Cancer refers to any malignant growth or tumor in the body, caused by abnormal and uncontrolled cell growth, with cancer cells continuing to divide and grow uncontrollably. Insulin resistance plays a role in this process, as it pushes cancer cells to grow faster.
Cancer cells thrive on two primary ingredients, namely glucose and insulin. The latest research indicates that dietary fat can also promote cancer growth and metastasis.
- Glucose: Cancer cells seem to have a sweet tooth, as they love glucose as their primary metabolic fuel. Cancer cells have the ability to also break down glucose outside the mitochondria, meaning that it doesn’t need oxygen in the blood stream to break down glucose as fuel, the way normal cells do. This allows cancer cells to grow rapidly anywhere in the body, including areas that might not have adequate oxygen containing blood flow.
- Insulin resistance: Insulin resistance results in elevated levels of insulin in the body and one of insulin’s main actions is to cause cells to grow. Cancer cells which have mutated to be more sensitive to insulin are growing much more rapidly than normal.
- Lipids (fats): Increasing evidence indicates that lipid metabolism is enhanced at different stages of cancer development. The excessive consumption of food rich in fat, particularly high levels of saturated fat found in typical Western diets, as well as obesity, are risk factors for cancer metastasis.
Certain types of cancer are more commonly linked to insulin resistance. Breast cancer and prostate cancer tumors have excess insulin receptors (six times more in breast cancer) than noncancerous tissue. Colorectal cancer patients with insulin resistance are roughly three times more likely to die from the cancer.
Insulin resistance affects aging, the skin, muscles, and bones.
Aging can be defined as the sum consequence of the cells in the body losing the ability to replenish themselves, with many factors playing a role, amongst them insulin resistance.
Laboratory studies have indicated that insulin resistance is adversely connected to longevity, but these findings may not apply to humans. However, it is known that the longest living humans are also the most insulin sensitive.
Cells in the skin are also sensitive to insulin and high levels of insulin increase melanin production to such an extent that the skin takes on a darker-than-normal tone. This darkening occurs most often where the skin rubs together and can also appear as large patches.
People with insulin resistance are also more likely to develop skin tags.
Psoriasis is a chronic inflammatory skin disease and people suffering from it are three times more likely to be insulin resistant.
People with acne have higher fasting levels of insulin in the blood than people without acne.
Hearing loss is one of the consequences of aging, but studies have found that inner ear function is compromised in people with insulin resistance.
Muscles are the largest insulin-sensitive tissue in the body. Insulin promotes muscle growth and maintenance, as well as being involved in regulating protein metabolism. When muscles become insulin resistant, they lose a potent growth signal, which potentially contributes to muscle loss, reduced muscle capacity, and decreased performance. Insulin resistance is suspected to also play a role in fibromyalgia, as researchers found that people with fibromyalgia are more likely to struggle with insulin and glucose control.
Although not much is known about bone insulin signaling, it is known that insulin helps to maintain bone mass.
In terms of joints, a study of overweight individuals has indicated that those ones with osteoarthritis were most likely to have the highest levels of insulin in the blood. High levels of insulin are also known to contribute to inflammation in the fluid in the joints.
As insulin resistance contributes to uric acid accruing in the kidneys instead of excreting it into the urine, it is a contributing factor to gout in the joints, commonly manifesting in the big toe.
Insulin resistance affects gastrointestinal and kidney health.
The body’s digestive and urinary tracts are involved in fundamental processes such as moving nutrients into and through the body, also in the elimination of waste that results from digesting and metabolizing these nutrients. The digestive and urinary processes become compromised when insulin resistance starts to change their functions, altering the way the body digest and absorb food, even changing how the kidneys filter waste products.
In the gastrointestinal tract, insulin resistance increases the risk of developing acid reflux and can also slow movement of food through the intestines, a condition called gastroparesis.
Insulin resistance impairs gallbladder function, which can lead to excess cholesterol accumulation that can form gallstones. The gallbladder also may not be contracting enough to push the bile into the intestines. The more insulin resistant a person is, the less the gallbladder contracts. Research has also shown that rising insulin resistance during pregnancy is the most predictive factor for developing gallstones during pregnancy.
When the liver becomes insulin resistant, it increases blood glucose (driving up insulin levels) and fats, as well as altering LDL cholesterol size, which can be detrimental to blood vessels. Excess insulin in the blood signals the liver to create excess fat, which the liver may store. When the liver stores too much fat, it will start to lose functionality. While a fatty liver is usually associated with excess alcohol consumption, a condition known as alcoholic fatty liver disease, a fatty liver can also develop without excessive alcohol intake, a condition known as nonalcoholic fatty liver disease. Being insulin resistant increases the risk of nonalcoholic fatty liver disease about 15 times and this condition can lead to serious liver conditions when the liver becomes inflamed, and it can potentially lead to liver failure.
A high fructose intake can have a similar fat accumulating effect on the liver as alcohol, so much so that this effect has been described as “fructose is alcohol without the buzz.”
Insulin resistance can affect the kidneys as well, as it contributes to the forming of kidney stones. High levels of insulin increase the amount of calcium in the blood and when freshly produced urine becomes supersaturated with calcium, the calcium starts to form crystals in the kidneys that become stones. (Beware the excruciating pain when kidney stones move down the urinary tract, which some claim is worse than the pain associated with childbirth!)
Insulin resistance affects metabolic syndrome and obesity.
Metabolic syndrome refers to a cluster of conditions that occur together, increasing one’s risk of heart disease, stroke, and type 2 diabetes. Together with insulin resistance, the patient must have at least three of the following conditions: excess body fat around the waist, high blood pressure, abnormal levels of cholesterol or triglycerides, and high blood sugar. Insulin resistance plays such a critical role in metabolic syndrome, that it used to be known as insulin resistance syndrome.
The connection between obesity and insulin resistance has been compared to a chicken-and-egg question of which happens first. Insulin is a critical factor when it comes to body fat, for when insulin levels are up, body fat is up, and if insulin is down, body fat goes down. Insulin directs nutrients in the bloodstream toward being stored as fat. It is also true that obesity leads to insulin resistance.
Conclusions:
Many diseases are associated with insulin resistance, and it has become the world’s most common health disorder. It is present in almost every chronic disease.
While this Health Insight blog focuses on insulin resistance as the root cause of most chronic diseases, other Health Insight blogs have covered various other aspects related to insulin resistance and are available to read on www.healthinsight.co.za, namely:
INSULIN RESISTANCE.
METABOLIC HEALTH.
THE EFFECT OF GENETIC MAKEUP, INSULIN RESISTANCE, AND TYPE OF DIET ON WEIGHT LOSS.
References:
Why we get sick. The hidden epidemic at the root of most chronic diseases – and how to fight it. Book by Dr. Benjamin Bikman. Published in 2021 by BenBella Books, Inc. Dallas, Texas. USA. P. 259.
HEALTH INSIGHT.
November 2024