There is some debate over the appropriate amount of carbohydrate in the diet of diabetics (and muggles for that matter). If you want the summary, here is link to tl;dr, otherwise keep reading.
On one side of the argument we have Dr Bernstein and the Type One Grit advocates. They promote very low levels of daily carbohydrate (around 30g) and see excellent control because of this. The risks of hyperglycemia are small because of the lack of carbohydrates and Dr. Bernstein argues the risk of hypoglycemia is small because of the correspondingly smaller amounts of insulin used and the strict control of the carbohydrate count at each meal (typically 6g/12g/12g for breakfast/lunch/dinner).
On the other side we have high carbohydrate advocates, such as Forks Over Knives and the unfortunately named ‘FOK Diet’. FOK promotes a plant-based diet high in carbohydrates and low in animal fats. The thinking here is to reduce insulin resistance in the body and, through this, provide better control. Clearly, the focus is on Type 2 diabetics but the FOK folk also promote this diet for Type 1s. The argument is that while control can be achieved through a low carbohydrate approach, the health cost of high levels of animal fats is too high; you are replacing one problem with another. Hypoglycemia is avoided by eating lots of carbohydrates. Hyperglycemia is avoided by making sure you eat low GI (glycemic index) foods, preferably plant-based. It should be noted that FOK do not say high levels of dietary carbohydrates are necessarily good or essential, they simply say high levels of animal fat are bad.
I am not intending to resolve this debate with this blog article but I do consider where the body gets its energy from and answer just how essential carbohydrates are. From there, it is up to you. In full disclosure, I do not eat a lot of carbohydrate. As a Type 1 LADA in honeymoon, I believe the best thing I can do for my pancreas is to give it as little work to do as possible and a low carbohydrate regimen achieves that.
What Foods Give Us Energy?
There are four main components of food which give us energy. These are:
- Fat (yielding 37 kJ/g or 9 kcal/g)
- Ethanol (aka alcohol) (yielding 29 kJ/g or 7kcal/g)
- Protein (yielding 17 kJ/g or 4 kcal/g)
- Carbohydrate (yielding 17kJ/g or 4 kcal/g)
There are a few other sources of energy, such as organic acids and alcoholized sugars, but we will keep things simple with the main ones.
What Food Gives Us Glucose?
Of these foods, the only ones which get converted to glucose are carbohydrates (whenever you eat them) and proteins (significantly when you are fasting via gluconeogenesis). For a recap of what gluconeogenesis is, refer to “What is Ketosis and Diabetic Ketoacidosis?” where I wrote in detail about how the body finds alternative sources of energy when fasting. In short, when there is insufficient dietary carbohydrate, the liver engages the following processes:
- Glycogenolysis: The release of glucose into the blood from the glycogen energy stores of the liver and muscles
- Gluconeogenesis: The conversion of amino acids from proteins into glucose
- Ketosis: The conversion of fatty acids from fat into ketones (an alternative fuel for some parts of the body)
So even if we are not eating carbohydrate, the liver can release glucose into the blood to fuel the body and, when this runs out, it can convert the body’s protein supplies.
What Food Elements Are ‘Essential’?
So we know, from an energy perspective we can possibly make do but perhaps carbohydrates are needed for something else. In fact, while proteins and fats are necessary to build the structures of the body, this is not the case for carbohydrates. Here are some of the uses of fats, proteins, and carbohydrates:
- Fats: Break down into fatty acids in the body and used for:
- Regulation of vitamin intake
- Hormone regulation
- Insulation and protection of organs
- Proteins: Break down into amino acids in the body and used for:
- Build structures in the body like muscles
- Facilitate communication between cells
- Act as transporters for other molecules
- Carbohydrates: Break down into glucose in the body and used for:
- Energy
That is it. Carbohydrates are used for energy or stored for use as energy later on. There is nothing essential about carbohydrates.
So, assuming you could eliminate carbohydrates, fats, or proteins completely from your diet, could you survive?
For carbohydrates, as we can make glucose from protein via gluconeogenesis, we know they are not essential.
For fats, there are two essential fatty acids: omega-6 and omega-3. Essential meaning the body cannot synthesize enough of them on its own to maintain function. Without omega-6 and omega-3 the body simply cannot function.
For proteins, there are nine essential amino acids. Of these, you may have heard of Phenylalanine, which is one on the substances the sweetener aspartame breaks down into. Another is Tryptophan, made popular by the myth that it causes the drowsiness of excess turkey eating.
Do Our Bodies Need Glucose?
There is a common myth that the brain requires carbohydrate to function. This is not true; the brain runs primarily on glucose, from any source but, more importantly it can also utilize ketones to run as an alternative fuel source in times when glucose is in short supply. In fact there are four main fuel sources the organs of the body can use to fuel themselves.
- Glucose (fuels the kidneys, brain, liver, fatty tissues, and muscles)
- Fatty Acids (fuel the muscles)
- Ketones (fuel the brain and muscles)
- Amino Acids (fuel the liver)
Source: https://www.ncbi.nlm.nih.gov/books/NBK22436/
Clearly glucose is the most versatile fuel source, covering all the bases but the only parts of the body solely dependent on glucose are the kidneys and fatty tissues. Everything else can supplement with alternatives.
I tried to find the maximum rates of glucose production possible through glycogenolysis and gluconeogenesis but came up short. Of particular interest is the rate of glucose production for gluconeogenesis because the liver only keeps enough glycogen stored for a couple of days. After that the only way for the body to generate glucose is through gluconeogenesis.
The story all students are told before going on school camp is the rule of three: you can survive three days without water and three weeks without food. If this is true, as we know glycogen stores are only good for a couple of days, this means the body can get by on gluconeogenesis alone until, presumably, the available protein stores run out. Of course, with enough protein in the diet, we can keep the glucose production going indefinitely.
tl;dr
Unlike fats and proteins, carbohydrates are not essential because the body has ways of generating glucose outside of the digestion of carbohydrates. This is not true for essential amino acids and essential fatty acids which are needed to maintain the health of the body and which can only be obtained by the dietary intake of proteins and fats, respectively.
Moreover, while the kidneys and fatty tissues rely exclusively on glucose for energy, the rest of the body can access alternative fuel sources, such as amino acids, fatty acids, and ketones.
Finally, we know the body can generate enough glucose for its needs outside of carbohydrate ingestion because a person can survive with no food for up to three weeks. Given the liver and muscle’s glycogen stores are only good for a couple of days this means the process of gluconeogenesis (the body’s conversion of amino acids to glucose) is all that is required to maintain blood glucose levels, and as long as a regular supply of protein is provided, this means the process can continue indefinitely.
You do not need to eat carbohydrates!
The Practical Diabetic 