Carbohydrates: The Macronutrient Guide
By Tyler Woodward
In this article, we will talk about everything you need to know about the essential macronutrient carbohydrates.
- The Difference Between each type of Carbohydrates
- How We Digest & Metabolize Carbohydrates
- How Insulin & Glucagon work together to regulate blood sugar
- Why Glucose Metabolism is optimal
- The Benefits of Carbohydrates
Table of Contents:
- What Are Carbohydrates?
- Digestion of Carbohydrates
- The Insulin & Glucagon Feedback Loop
- Are Carbohydrates Bad For You?
- The Benefits Of Consuming Carbohydrates
What Are Carbohydrates?:
Carbohydrates or more commonly referred to as carbs are one of the three main macronutrients. Carbs are composed of the elements carbon, hydrogen, and oxygen and contain 4 calories per gram. Carbohydrates are the body’s primary fuel source and are essential to maintaining a healthy metabolism. Carbohydrates can be separated into two categories, simple and complex carbs.
Simple Carbs are all types of sugar and can also be split up into monosaccharides or disaccharides. The three forms of monosaccharides are glucose, fructose and galactose. When any two of these monosaccharides are combined you will get a disaccharide. The three most common disaccharides are lactose, maltose, and sucrose.
- Glucose + Galactose = Lactose
- Galactose + galactose = Maltose
- Fructose + Galactose = Sucrose
Simple sugars are found in large quantities of many of the fruits and vegetables that we eat.
When we combine thousands of these simple sugars together into one molecule we produce polysaccharides. Animals mainly use these complex carbs to form glycogen which is our main source of energy storage. Plants use polysaccharides to form a number of structures including starch's and cellulose. Starch is used by plants for energy storage while cellulose is a structural molecule that makes up their cell wall. Chitin is another type of polysaccharide that also contains nitrogen which many animals use to build their exoskeleton like insects, crabs or the scales of fish.
As humans we do not have the digestive system or the enzymes required in order to digest cellulose and therefore commonly refer to it as insoluble fiber, meaning it does not break down in water. Since we do not have the capability to break down cellulose we are unable to extract any significant amount nutrients from leaves and stems like broccoli, kale, spinach or lettuce. In contrast, ruminant animals like cows, sheeps, goats and buffalo have a four chambered stomach and produce the enzyme cellulase which allows them to extract all the necessary nutrients out of grass.
What About Processed/Refined Sugars?
Processed sugars typically consist of pure sucrose which is composed of one glucose molecule and one sucrose molecule. Refined sugars aren’t necessarily bad for you, but they are stripped of most of the vitamins and minerals that are normally found with naturally occurring carbohydrates and sugars. They will still be processed in the same way as all other sugars in the body and can therefore be used as energy, but they are not very nutritious. High fructose corn syrup on the other hand is not a purely refined sugar and is turned into a liquid, starchy mix. Additionally, unlike in regular sucrose, the fructose and glucose that are present in high fructose corn syrup are not physically bound to one another. This results in high fructose corn syrup being liquid at room temperature. High fructose corn syrup is generally best to be avoided.
Digestion Of Carbohydrates:
When consumed glucose is directly absorbed into the bloodstream as blood glucose or blood sugar and galactose is quickly converted into glucose in the body. Fructose is directly absorbed by the liver where it will either be metabolized for fuel or converted into glycogen for energy storage.
Disaccharides also require very little work to be digested and only need to be split apart into its two respective sugar. Some people stop producing the enzyme lactase after infancy and over time lose their ability to digest lactose. This is known as lactose intolerance and is significantly more common in East Asian countries where consuming dairy products as adults is much less common compared to European and countries in the Western hemisphere.
Complex carbohydrates on the other hand like starch must be fully broken down into the monosaccharides that make them up. This takes much longer to occur compared to the simple sugars due to the hundreds of sugar molecules bound together in complex carbs. Again, we humans do not have the digestive enzymes required to break down cellulose, so it just passes through our digestive tract and cannot be converted into energy.
The Insulin & Glucagon Feedback Loop:
When we consume large amounts of sugar our blood glucose levels rise which signals to our pancreas to produce insulin. Insulin directs our cells to absorb the glucose present in our bloodstream to be used as energy. Insulin also down regulates the amount of fatty acids in the bloodstream, so glucose can be more easily absorbed into the cell. Any excess glucose that is not currently needed will be converted into glycogen or at times fat, as a form of energy storage. A few hours after eating or during exercise our blood glucose levels begin to decrease. This triggers our pancreas to begin to release glucagon which signals to our cells to convert the stored glycogen back into glucose to be used as fuel.
The Glycemic Index:
The glycemic index is a measuring tool to assess how much specific foods will increase your blood sugar levels irrespective of the quantity of food you consume. The foods highest on the GI index will always be the foods that contain the highest amount of pure glucose. Because fructose is absorbed directly by the liver, it does not cause an increase in blood sugar and actually helps to keep your blood sugar levels down when consumed with glucose. Starches which are made up of pure glucose will also tend to be higher than fructose containing foods, but will rank lower on the GI due to insoluble fiber or fat content that slows down their digestion. Meaning it takes longer for all of the glucose in complex carbs to reach the blood and therefore for your blood sugar levels to rise.
Consuming protein by itself, particularly in large quantities, also causes an increase in the release of insulin. For this reason it is best to consume some form of carbohydrates with your protein typically in a 2:1 or 3:1 ratio of grams of carbohydrates to grams of proteins. For example, if you consume 20 grams of protein you would want to consume somewhere between 40-60 grams of carbs.
The Glucose (Oxidative) Metabolism:
As mentioned before, our body’s primary and preferred fuel source is glucose. Our body is able to convert glucose into large amounts of energy in the form of ATP (Adenosine triphosphate) through a process known as cellular respiration. The release of large amounts of carbon dioxide as a byproduct of the glucose metabolism encourages the cell to absorb more oxygen from the bloodstream as CO2 is released. This results in a positive feedback loop as more CO2 is released, more oxygen is absorbed and the more glucose is broken down to yield further energy
As long as there is adequate glucose supply in our bloodstream our cells will continually uptake glucose to convert into energy. When our blood runs low on glucose and glycogen our cells are forced to shift to other forms of metabolism to produce energy through fatty acid metabolism (converting fat to energy) or gluconeogenesis (the conversion of protein to glucose). Both of these processes are much less efficient than glucose metabolism, producing a lot less energy and a lot more stress hormones as a byproduct.
Are Carbohydrates Bad For You?:
To understand why carbs are not bad and in fact very healthy for us to eat, it’s a lot easier to look at what happens when we do not eat them.
When we do not eat carbohydrates our body slowly begins to deplete our body’s glycogen stores, as we haven't consumed any glucose to replace them. At this time our body begins to release stress hormones in the form of cortisol and adrenaline to signal the release of fatty acids into the bloodstream. If we remain in this state for a prolonged period of time our body also begins to produce ketones. Ketones are a signaling agent to the body that it is starving due to this lack of glucose. At this point stress hormones like cortisol and adrenaline begin to take over turning on our body’s built-in backup system, so we can survive with little to no carbohydrate intake. The longer we remain in this state, the more stress is placed on our body.
The keto diet purposely aims to put our body into this state of ketosis by consuming very little carbohydrates. Due to the lack of carbohydrates present in the keto diet it typically results in short-term weight loss, but not fat loss! Glycogen in our cells regulate water retention, so as we deplete our glycogen stores on the keto diet we rapidly lose water stores as a byproduct.
Additionally, as we consume very few carbohydrates over a period of time the amount of fatty acids in our blood stream increases. When we reintroduce carbohydrates and thereby glucose into our diet these fatty acids compete with glucose to enter the cell. This causes our cells to become more insulin resistant, meaning that our cells do not respond to insulin as strongly and will absorb less glucose as a result. To combat this our pancreas begins to produce more insulin in order to maintain normal levels of blood glucose. This cycle of increased insulin resistance is known as the Randall Cycle and may contribute to the development of Type II diabetes. Type II diabetes occurs when exogenous (made from outside the body) insulin is required to maintain normal blood glucose levels because our body cannot produce enough on its own.
To learn more about the pitfalls of the Keto Diet and why consuming carbohydrates is necessary for optimal health, make sure to check out Christopher Walker's new book, "The Thermo Diet: How To Eat," available on UmzuFit.
The Benefits Of Consuming Carbohydrates:
- Packed With Micronutrients - Carbohydrate dominant foods like fruits, roots and tubers tend to be very micronutrient dense due to the high amount of vitamins, minerals and antioxidants present in these foods. If we forego these foods for a prolonged period of time we become highly susceptible to micronutrient deficiencies which can result in a ton of health issues, inflammation and a lowered metabolism.
- Protein Sparing - When we are deficient in carbohydrates our body is forced to turn to fatty acids and amino acids to utilize as fuel through a process known as Gluconeogenesis. Amino acids are the building blocks of proteins. So by consuming adequate carbohydrates we can prevent the breakdown of protein in our cells and ensure there are enough amino acids present to build new proteins.
- Increased Energy & Metabolic Rate - As we discussed previously, the metabolism of glucose is part of a positive feedback loop that leads to increased oxygen uptake and more energy production. For more information on this, make sure to check out our article, "Sugar Is Good For You | The Power Of Sugar For The Metabolism".
- Improved Sleep Quality - Since we do not eat during our sleep our body must rely on its glycogen stores to fuel itself throughout the night. Having enough glycogen stores and thereby energy allows our body to recover efficiently and produce large amounts of pro-metabolic hormones like T3/T4, testosterone and progesterone throughout the night.
- Reduced Inflammation & Oxidative Stress - Sugar is actually an antioxidant and can help to reduce oxidative stress by binding to free radicals present in the body. Additionally, carbohydrates are required by the body in order to produce the “master” antioxidant glutathione.
Do Not Confuse Carbs/Sugars with PUFAs!
If you read my article, “Fats: The Macronutrient Guide,” you will understand the detriments of consuming polyunsaturated fats (PUFA’s). Due to the double bonds present in PUFA’s they are readily broken down and oxidized in the body into free radicals because of our naturally high body temperature. Sugar often takes the blame as to why foods like cookies, cakes and all other sugar delights are so “bad” for you. In reality the sugar in these foods gets broken down into fuel while the PUFA’s present get oxidized into free radicals causing inflammation, insulin resistance among a string of other health issues. It should be noted that the sugar used to make the majority of baked goods is processed sugar, which means that it is “pure sugar” and is stripped of the micronutrients that carbs and sugars are naturally found with in nature.
My goal in writing this article, as always, is to provide you with logically-based principles that you can use to form your own conclusions regarding any information you may come across within this subject. I really hope you found this article interesting and if you have anything to add to this article, or any comments or criticism, feel free to reach out to me on our facebook groups (The Thermo Diet Community Group, The UMZU Community Group) or on Instagram @tylerwoodward__. Also, please feel free to share this article with anyone that might be interested.
Thanks for reading!
Until next time… be good
B.S. Physiology & Neurobiology