Does Cutting Down on Carbs the Answer to Curing Diabetes and Insulin Resistance?
Maybe this is new news, maybe this is old news — regardless, diabetes is ranked as one of the top 10 causes of death around the world. A long time ago, diabetes was labeled as ‘adult onset’ as the medical community tended to find that older patients had diabetes and was not seen in children. Sadly, today, diabetes in children is a common occurrence!
Over the years, I’ve met more and more people with diabetes and many of them are trying a low-carbohydrate diet. This got me wondering what is diabetes and how would a low-carbohydrate diet help?
There are different types of diabetes and we’ll focus on type 2 diabetes mellitus (T2DM), which is the most common type of diabetes consisting of ~90–95% of all diabetic cases. T2DM is a chronic metabolic disease that is diagnosed by a physician using the following criteria:
- a person’s blood glucose level is high (hyperglycemia),
- there is an increase in red blood cells with glycated hemoglobin (HbA1c),
- and/or the body is insensitive to insulin (insulin resistance).
Let’s unpack all these to learn more about the inner workings of diabetes:
What is glucose and insulin?
Glucose is one of many simple carbohydrates that are from the food we eat. In unrefined whole foods like strawberries or oats, glucose is attached to other glucoses to form complex carbohydrates like starch (a polysaccharide or “many sugars”) or attached to fructose to form sucrose (disaccharide or “two sugars”). In processed foods like candy or soda, most of the carbohydrate comes from table sugar or high fructose corn syrup, which both consist of many, many sucrose molecules and very little complex carbohydrates.
When we eat foods that contain starchy or sucrose carbohydrates, our small intestine releases enzymes, like amylase, that separates glucose from other glucose or fructose molecules. These separated glucose and fructose molecules are then absorbed into the bloodstream (we will talk about fructose another time). This causes blood glucose levels to rise. Depending on whether the food has more simple or complex carbohydrates will determine how fast blood glucose levels will rise. Foods like strawberries and oats will raise the blood glucose levels slower than candy and soda. Scientists have measured different foods and their effects on blood glucose levels. This measurement is called the glycemic index. The higher the glycemic index of a food, the faster that food would increase blood glucose levels. Pure glucose has a glycemic index of 100 whereas strawberries has a glycemic index of 40.
The rise in blood glucose signals the body to produce insulin. The role of insulin is to help the body’s organs, like the liver and muscles, to absorb the blood glucose and lower the blood glucose levels. So every time we eat food that contains starch or sucrose, they get broken down into glucose, which gets absorbed into the blood. Insulin then signals the liver and muscle to take in the blood glucose. This lowers the blood glucose level back to normal.
Why measure blood glucose?
A blood sample can be measured for how much glucose is in the blood at a single point in time (when the blood is drawn). This laboratory test usually is done when a person has fasted for at least 12 hours and is called a fasting blood glucose test. The person’s blood glucose level is then compared to a reference range that determines if the person has a healthy or unhealthy amount of glucose in the blood. For this fasted blood glucose test, an unhealthy blood glucose level is a value more than 100 mg/dL. A physician may diagnose the person as pre-diabetic if the value is between 100 to 125 mg/dL or diabetic if the value is more than 125 mg/dL.
There is a limitation on measuring blood glucose at a single point in time as other factors could have made the blood glucose levels high — maybe the person didn’t fast or was on a medication that raises blood glucose. Another test that measures the average blood glucose levels over a 3 month period is the hemoglobin A1c (HbA1c) test. Red blood cells contain hemoglobin and they play an important role in carrying oxygen in our blood stream. Sometimes hemoglobin and blood glucose meet and connect with one another forming glycated hemoglobin. This connection is forever until the red blood cell dies, which is usually less than 4 months. If a person’s blood glucose levels stay high for a long time, it is easier for a red blood cell’s hemoglobin and blood glucose to meet and connect.
A blood sample can also be run in a HbA1c test and measure how many red blood cells have their hemoglobins connected with blood glucose. The more glycated hemoglobins there are, the more likely the person’s blood glucose levels were high for a long time. A physician may diagnose the person as diabetic when more than 6.5% of red blood cells have glycated hemoglobin. So, a person is diagnosed diabetic when more than 65 out of 1000 red blood cells have glycated hemoglobin.
Both high blood glucose levels (more than 125 mg/dL) and a high amount of glycated hemoglobin (more than 6.5% HbA1c) can cause damage to the body over many years if left unchecked. Such diabetic complications can include damage to the kidneys (diabetic nephropathy), nerves (diabetic neuropathy), eyes (diabetic retinopathy), and blood vessels (atherosclerosis) resulting in a kidney that doesn’t filter properly, loss of muscle control, blindness, and stroke.
Why then are individuals with T2DM unable to use their insulin to lower blood glucose levels? How does insulin resistance happen?
Individuals with T2DM tend to either be overweight or obese, which means they have a high amount of fat. If an individual consumes more calories than they need, he or she will gain weight. When we eat food or drink a calorie-rich beverage, the body can store the excess fat and carbohydrate calories into fat cells called adipose tissue. This gives the body the ability to store energy when needed. If an individual continues to have more calories than he or she needs, over time the fat cells will be filled up and the body will need to find other areas to store the excess calories. This leads the body to create more fat cells in places like the liver, pancreas, and muscles. This may sound innocent but these organs weren’t meant to have so many fat cells near them. These fat cells end up being bad neighbors by throwing their trash outside and ruining their neighborhood. This trash contributes to what scientists call lipotoxicity (“fat poisoning”) and consist of lipid intermediates like diacylglycerol and ceramides. These lipid intermediates block insulin from allowing blood glucose into the liver, pancreas, and muscles; which keeps blood glucose levels high. This means that an individual with T2DM has insulin resistance because their organs aren’t able to absorb the blood glucose. By having too many fat cells all over the body, insulin resistance occurs and blood glucose levels stay high when eating carbohydrate-rich foods and drinks.
If blood glucose is the issue, does a low-carbohydrate diet prevent diabetes?
It seems that by removing carbohydrate from the diet would result in no glucose being absorbed into the blood. A study done by Saslow et al. had patients with T2DM go on either a ketogenic diet or moderate-carbohydrate diet and found that those on a ketogenic diet had reduced HbA1c levels. This should make sense as the ketogenic group shouldn’t have eaten much carbohydrate to cause their red blood cell’s hemoglobin from binding with glucose as very little glucose would be in the blood. This might be okay if these individuals don’t expect to eat any carbohydrate for the rest of their life. If and when these individuals decide to eat carbohydrate, their insulin resistance might be worst than before since they may end up having more fat calories being stored in fat cells causing lipotoxicity. Scientists have termed the continual increase in insulin resistance even without high blood glucose levels as starvation diabetes. While a low-carbohydrate, high-fat (ketogenic) diet can prevent blood glucose levels from being high, such a diet isn’t able to help with the insulin resistance experienced by individuals with T2DM.
So does cutting out carbs from a diet cure diabetes and insulin resistance?
If we define T2DM as chronic high blood glucose levels, then a low-carbohydrate, high-fat (ketogenic) diet seems to keep blood glucose levels in check. Yet the ketogenic diet does not address the underlying cause of T2DM, which is insulin resistance. If an individual with T2DM does not lose weight in the form of fat, an individual with T2DM on a ketogenic diet may continue to store fat in the liver, pancreas, and muscles; which not only increases insulin resistance but may contribute to fatty liver disease, an inflamed pancreas, and muscle loss. So it seems that cutting out carbs from a diet may “cure” high blood glucose levels, but it does not solve insulin resistance and may also cause other damages to the body.
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