Macronutrient Series: Carbs
In this blog post series, you’ll learn about the three major macronutrients (carbohydrates, fats and proteins) and why they’re important to your health. Each macronutrient has a significant impact on our energy levels, performance, recovery, disease risk, body composition and more. In this post, we’ll be covering carbohydrates.
Macronutrients are nutrients the body requires in large amounts. Carbohydrates are one of the three macronutrients that make up most of the food we eat. These molecules effect many physiological processes in our body such as…
Digestion & absorption of nutrients
Cell structure & function
Let’s look at how carbohydrates play a role in these processes.
What is a Carbohydrate?
Carbohydrates are known as saccharides (latin saccharum or sugar) and are divided into 3 groups based on the complexity of their chemical structures.
Monosaccharides: simplest form, containing 1 sugar group. Glucose, Fructose, Galactose, Mannose and Ribose are examples of monosaccharides.
Oligosaccharides: more complex, contain two monosaccharide units links together to form “disaccharides” or three monosaccharides linked together to form “trisaccharides”. Sucrose, Maltose, Lactose and Trehalose examples of oligosaccharides.
Polysaccharides: very complex, long chains of linked monosaccharides units. Starches (amylose & amylopectin) , Glycogen and Fiber are examples of polysaccharides.
Digestion, Absorption, Transport & Metabolism
Carbohydrates must be broken down into monosaccharides for us to digest them. The digestion process first takes place in the mouth with the help of an enzyme known as salivary amylase. Salivary amylase helps with 20% of the breakdown process. If we spend more time chewing our food, we’ll give salivary amylase more of a chance to break down our food. Even in non-”sugary” carbohydrates, after chewing for an extended period of time, you’ll start to taste a sweetness!
Carbohydrates then travel down through the esophagus into the stomach where they are mixed in an acidic bath mixture known as chyme. No digestion takes place here, only the destruction of any harmful pathogens that might be on the carbohydrates.
Once in the small intestine enzymes known as pancreatic amylases begin turning the carbohydrate chains into disaccharides.
Maltase: breaks down maltose into two monosaccharide units of glucose
Lactase: breaks down lactose into the monosaccharides glucose and galactose
Sucrase: breaks down sucrose (table sugar) into glucose and fructose monosaccharides
At this point the carbohydrates are monosaccharides and are absorbed into the bloodstream. The liver stores lots of glucose molecules together in a storage form of glucose is known as glycogen. Our bodies store 80-100g of glycogen in the liver and 300-600g in the muscles (depending on how much muscle mass someone has) . We move about 20g of glucose through our blood every hour (“blood sugar”).
Once glucose has entered the bloodstream it can be sent throughout the body to provide a fuel source for the body. Glucose is the body’s main energy source when not at rest ,meaning carbohydrates are vital for allowing us to expend energy! Without glucose, we cannot provide energy to our cells in order to maintain our physiological processes, create movement, and nearly any other energy dependent function. While the body can “create” (we can alter other macronutrients to become glucose), carbohydrate intake is the quickest and easiest pathway to providing energy.
The glycemic index (GI), is a measure of the rate of which an ingested food causes the level of glucose in the blood to rise when we consume 50g of usable carbohydrate. The less processed and high fiber foods (legumes, whole grains & vegetables) are more complex in structure. As a result, they take longer to digest and have a lower GI value. High GI value foods such as processed foods, sugar, cereal, high fructose corn syrup and candy digest quickly, thus raising the blood sugar fast. Repeated quick elevation of blood sugar can lead to many health concerns over the long term, most notably Type 2 Diabetes.
The glycemic index doesn’t tell the whole story of physiological response to carbohydrate. This is because we don’t eat carbohydrates in isolation of protein, fat and fiber which all change the GI response. A variety of the other factors affect how quickly a food is converted into glucose…
Timing of the meal
We need glucose to survive and thrive. Our brains require 130g of glucose per day. There is no “set” amount of carbohydrates that is the same for everyone. The appropriate amount of carbohydrate intake will depend on…
Lean body mass compared to body fat
Size of a person
Activity levels & Frequency
Intake levels of other macronutrients
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Sources: Berardi, J., Andrews, R., St. Pierre, B., Scott-Dixon, K., Kollias, H., & DePutter, C. (n.d.). The Essentials of Sport and Exercise Nutrition (3rd ed.).
Chek, P. (n.d.). How to Eat, Move and Be Healthy!
Rakel, D. (n.d.). Integrative Medicine (4th ed.).